T H E M I D D L E J... S T O N E S F I E L...

T H E M I D D L E J U R A S S I C F L O R A F R O M

S T O N E S F I E L D , O X F O R D S H I R E , U K by

C . J . C L E A L and

P . M . R E E S

A

BSTRACT.

The Stones®eld `Slate' of Oxfordshire has yielded a diverse Middle Jurassic ¯ora, containing 25 morphospecies, dominated by remains of araucariacean and cheirolepidiacean conifers, bennettitaleans, and leaves of the possible gymnosperm Pelourdea . It mainly represents coastal vegetation, which included mangrove-like stands of Ptilophyllum , and conifers probably growing in lowland coastal habitats that were subjected to periodic waterstress. The Pelourdea leaves may have drifted in from drier, more upland habitats. The ¯ora is similar, but not identical to, the slightly older ¯oras from the Cotswold `Slate' of Gloucestershire, such as from Eyeford and Sevenhampton.

Also comparable are the contemporaneous ¯oras preserved in marine deposits in France and the Venetian Alps of Italy.

It is quite different from the Middle Jurassic ¯ora of Yorkshire, which is thought to represent vegetation growing in deltaic habitats. The new combinations Ptilophyllum pectiniformis (Sternberg), Komlopteris speciosa (Ettingshausen) and Pachypteris macrophylla (Brongniart) are proposed for species found at Stones®eld.

Nilssoniopteris solitarium

(Phillips) comb. nov. is proposed for the species previously named Nilssoniopteris vittata (Brongniart).

Taeniopteris vittata Brongniart is retained as the type species of Taeniopteris , a morphogenus to be used for entire cycadophyte leaves that cannot be de®nitely assigned to the cycads or bennettitaleans.

Conites is shown to be an earlier nomenclatural synonym of Bucklandia , to be used for casts and compressions of cycadophyte stems. This requires a number of new combinations for species that have hitherto been included in Bucklandia : Conites anomala (Stokes and Webb), C. gigas (Seward), C. indica (Seward), C. milleriana (Carruthers), C. pustulosa (Harris) and C. yatesii

(Carruthers).

KEY WORDS

: Jurassic, palaeobotany, impressions.

T

H E

Middle Jurassic tilestones of Stones®eld in Oxfordshire, traditionally known as the `Stones®eld

Slate', have yielded one of the most intensively studied assemblages of Jurassic plant fossils in Britain.

Specimens from here have been studied since the early nineteenth century, culminating in the monograph by Seward (1904). However, the early years of the twentieth century saw a major shift in emphasis in the study of Mesozoic palaeobotany, with the discovery of the importance of cuticle studies (e.g. Thomas and

Bancroft 1913). Very occasionally, cuticles are preserved in Stones®eld fossils (Kendall 1949) and Hill

(1986, ®g. 9.3) has shown that epidermal structure can sometimes be observed impressed in the matrix. In general, however, this material is not suited to cuticle and epidermal studies. A further problem is that it is effectively impossible to obtain further specimens from Stones®eld. The original material was mostly obtained from underground workings that closed a century or so ago (some of the pits have been recently re-opened, but not to work the tilestones, and it is not possible to collect there). Consequently, interest in the Stones®eld plant fossils has waned and few papers have been published on them over the last halfcentury. The decline in interest has been dramatic; in the nineteenth century, Stones®eld was regarded as the most signi®cant British Jurassic plant fossil site (Seward 1904), whereas most recent reviews of

Jurassic palaeobotany (e.g. Vakhrameev et al . 1978; Vakhrameev 1991) just do not mention it.

Nobody would claim that the Stones®eld plant fossils match their Yorkshire counterparts in palaeobotanical signi®cance. They are nevertheless of interest for a combination of historical, taxonomic and palaeobiogeographical reasons, and Stones®eld has been designated a protected site for its palaeobotanical interest (Site of Special Scienti®c Interest: Cleal 1988; Cleal et al.

2001). The ¯ora does not, therefore, deserve the virtual oblivion to which it has been delivered. Seward's work is still the de®nitive account of the ¯ora, but lacks photographic illustrations and is considerably out of date. The present paper provides

[Palaeontology, Vol. 46, Part 4, 2003, pp. 739±801, 15 pls] q The Palaeontological Association

740 P A L A E O N T O L O G Y , V O L U M E 4 6

TEXT-FIG.

1. Palaeogeographical map of southern Britain during the middle Bathonian, showing position of Stones®eld between the Welsh, Cornubian and Anglo-Brabant landmasses (shaded).

the ®rst comprehensive photographic record of the ¯ora and attempts to place it in the context of modern taxonomy, biostratigraphy and palaeobiogeography. The account is based on the two major collections, now stored in The Natural History Museum, London (NHM) and the Oxford University Museum (OUM).

The discussion is limited to the fossils from Stones®eld and its immediate surrounds, and does not cover the fossils from similar deposits found at Eyeford and Sevenhampton Common in Gloucestershire. Seward

(1904) referred to these deposits as `Stones®eld Slate', but in fact they are in the stratigraphically lower

Charlbury Formation (Boneham and Wyatt 1993). While the assemblages from these Gloucestershire sites are similar, they are not identical in composition and lumping them all together may lead to misleading interpretations.

This is not intended as a comprehensive review of each species found at Stones®eld as so many of the synonymies are not complete. The synonymies as normally only list the publication of the protologue of the basionym (marked *), any published illustrations of the type (marked T), and any published records of specimens from Stones®eld (marked } ). Otherwise, only references that are critical for understanding the taxonomy of the species, especially as they relate to the Stones®eld material, are included. The taxonomic hierarchy used is based mainly on that given in Cleal and Thomas (1999).

G E O L O G I C A L B A C K G R O U N D

The fossiliferous tilestones known as the Stones®eld Slate were mined at several sites in the vicinity of

Stones®eld village (National Grid Reference SP 394173; 51´8 8 N, 1´4 8 W), 17 km north-west of Oxford

(Text-®g. 1). They are of variable lithology, ranging from calcareous sandstone to siltstone, with impersistent oolitic laminae. They have a characteristic ®ne, horizontal lamination that allowed the splitting of the `slates'. There is also often a distinct, ®ne cross-lamination. The association of marine and non-marine animal fossils and terrestrial plant fossils suggests that they were deposited in a shallow,

C L E A L A N D R E E S : M I D D L E J U R A S S I C F L O R A

TEXT-FIG.

2. Generalized sequence through the Middle

Jurassic Great Oolite Group of Oxfordshire, showing the main levels that contain strata in the Stones®eld `Slate' facies (marked in black). (Adapted from Boneham and

Wyatt 1993, ®g. 2).

741 near-shore marine setting. Sellwood et al.

(1986) interpreted them as having formed in a narrow `gulf' extending north-east from the main South England Basin.

Poor exposure has hindered the establishment of a coherent stratigraphical framework for the

Stones®eld deposits. Even when the tilestones (`slates') were being mined, relating the sequences seen in the various adits and shafts proved dif®cult. Various and often contradictory stratigraphical schemes were proposed (Fitton 1828; Hull 1859; Horton 1860; Woodward 1894; Walford 1894, 1895, 1896; Arkell

1947; Sellwood and McKerrow 1974). However, our understanding of the stratigraphy improved dramatically when a series of boreholes were drilled in the area during the early 1990s (Boneham and

Wyatt 1993). It had been believed that the Stones®eld Slate was a discrete member of the Sharp's Hill

Formation (Great Oolite Group) but the boreholes showed that it is in fact a facies occurring at different levels within the lower Great Oolite. The mined tilestones that yielded the plant fossils occur at three levels within the Taynton Limestone Formation (Text-®g. 2). The tilestones have yielded ammonites of the

Procerites progracilis Zone, placing them in the lower part of the Middle Bathonian (Torrens in Cope

1980).


H I S T O R I C A L B A C K G R O U N D

Much of the early palaeontological work at Stones®eld was by William Buckland, who was at nearby

Oxford University between 1801 and 1845, eventually becoming the ®rst Professor of Mineralogy. For many years, Buckland visited Stones®eld in the spring to see what had been revealed in the previous year's worked stone after the winter's frosts had had their effect. His main interest was the animal fossils, particularly vertebrates, but he also collected the plants. He published a preliminary list of plant species in

1824, and mentioned in passing some Stones®eld plants in his 1829 paper on the bennettite trunks from

Portland. However, his most important action was to send drawings of the Stones®eld plant fossils to some of the leading palaeobotanists of the day, in particular Sternberg (1823, 1825, 1833, 1838; see KvacÏek and

StrakovaÂ 1997), Brongniart (1823, 1828 a , b , 1831, 1833), and Lindley and Hutton (1835, 1837). Phillips

(1855, 1871) reviewed the palaeobotany of Stones®eld, partly based on the above works, but also including some new species. Other contemporary reviews were by Morris (1841, 1854) and Horton (1860), but they provided little newinformation.

During the middle nineteenth century, the British Museum (Natural History) started to accumulate its collection of Stones®eld plant fossils, which was initially studied by Carruthers (1867 a , 1869, 1870). One of the specimens (a conifer bract, Araucarites brodei ) was also ®gured in the ®rst English language palaeobotanical textbook (Balfour 1872). A catalogue and description of the Stones®eld ¯ora (included details of both the BMNH and Oxford collections) was prepared by Seward (1904). There are several weaknesses with the work. He regarded the tilestones from Sevenhampton and Eyeford as being the same as those of Stones®eld, and thus described the plants as a single ¯ora. There are no photographs, although the drawings are of high quality. Clerical errors in the synonymy lists have caused some nomenclatural confusion. Nevertheless, this is still the primary reference to the Stones®eld ¯ora.

There was little subsequent work on the palaeobotany of Stones®eld other than brief accounts of individual taxa (Edwards 1928; Kendall 1949; Florin 1958; Barnard 1968; Elliott 1979). Arkell (1947) mentioned the Stones®eld fossils, but added no newinformation. The only signi®cant contribution was

Kendall's work on the conifers as she managed to obtain some cuticles. Hill (1986, ®g. 9.3) illustrated stomata in Stones®eld conifer foliage (see also Shute and Cleal 1987, ®g. 3), further demonstrating the potential for anatomical studies there. Most recently, brief reviews of the ¯ora have been given by Cleal and Rees (1998) and Cleal et al.

(2001).

P R E S E R V A T I O N O F F O S S I L S

The fossils are preserved as impressions ( sensu Shute and Cleal 1987), sometimes picked out by iron staining or other mineralization. The quality of preservation is highly variable, depending mainly on the nature of the matrix. In the coarser type of matrix, the fossils will often show little more than the outline of the pieces of plant. However, plants preserved in a ®ner matrix may show the impression of epidermal structure (e.g. Hill 1986). Cuticle fragments have been found in some conifer shoots (Kendall 1949) but these are rare.

S Y S T E M A T I C P A L A E O N T O L O G Y

Division

PTERIDOPHYTA

Class PTEROPSIDA

Order

FILICALES

Family DIPTERIDACEAE Seward and Dale, 1901

Genus DICTYOPHYLLUM Lindley and Hutton, 1834

Type species .

Dictyophyllum rugosum Lindley and Hutton, 1834.

Remarks . This is one of a range of morphogenera for fossil dipteridacean fronds, distinguished mainly on a combination of the degree of division of the frond and characters of the sori.

Dictyophyllum is

C L E A L A N D R E E S : M I D D L E J U R A S S I C F L O R A 743 characteristically once pinnate with polygonal vein-meshes, and has minute and crowded sori (Harris

1961 a ; Rees 1993 a ). Very similar is Thaumatopteris GoÈppert, 1836, which can only be reliably separated from Dictyophyllum in the fertile condition, the sori being larger and more widely spaced.

cf.

Dictyophyllum sp.

Plate 1, ®gure 1

Material . OUM J.43275.

Description . A single fragment of a pinnati®d segment, 25 mm long and 10 mm wide. The rachis is 0´6 mm wide. The lobes are subfalcate, leaning apically, with apices that vary from subacute to rounded. The distance between the lobes

(measured between the points of attachment of the midveins) varies from 4´1±4´9 mm. The distance from the base of primary vein to the lobe apex is 4´8±6´3 mm. The distance between the rachis and the sinus separating the lobes varies from 2´1±2´4 mm, measured perpendicular to the rachis. Venation obscure. The primary vein arises from rachis at about 45 8 , and bears secondary veins at 70±80 8 . Higher order venation obscured by matrix and fracturing of what little phytoleim is present.

Remarks . This is the only known example of a dipteridacean fern fragment from Stones®eld. We have followed Seward (1904) in assigning it to Dictyophyllum but, in view of the small size of the fragment and the poor preservation of the venation, it has been assigned there with a `cf.'. Similarly small fragments of the bipinnate frond Goeppertella OÃishi and Yamasita, 1936 would be almost impossible to distinguish

(Rees 1993 a ).

Family MATONIACEAE Presl, 1847

Genus

PHLEBOPTERIS

Brongniart, 1837

Type species .

Phlebopteris polypodioides Brongniart, 1837.

Remarks . This is the commonest representative genus of the Matoniaceae in the Mesozoic, ranging from the Triassic to the Cretaceous. The closest comparison is with Matonidium Schenk, 1871, which is abundant in Middle Jurassic±Early Cretaceous ¯oras, and is thought to be an evolutionary intermediate between Phlebopteris and the extant Matonia R. Brown (Hirmer and HoÈrhammer 1936). They are best distinguished on the soral characters, in particular that there is a small but distinct indusium in Matonidium but none in Phlebopteris (van Konijnenburg-van Cittert 1993).

Phlebopteris also often has anastomosed veins, whereas in Matonidium the veins are always free. However, this is not always a reliable distinguishing characteristic as some early Phlebopteris species also have non-anastomosed veins (van

Konijnenburg-van Cittert, pers. comm. 2000).

Seward (1904) referred the Stones®eld fossils of this type to the morphogenus Laccopteris Presl, in

Sternberg 1838, following common usage at that time. However, it is now generally recognized that

Phlebopteris is the earlier valid synonym.

Phlebopteris woodwardii Leckenby, 1864

Plate 1, ®gures 2±3

*1864 Phlebopteris Woodwardi Leckenby, p. 81, pl. 8, ®g. 6.

} 1871 Taeniopteris angustata Phillips, p. 168, diagram 28, ®gs 8±10 ( vide Seward 1904).

1899 Laccopteris Woodwardi (Leckenby) Seward, p. 198; text-®g. 9 A .

} 1904 Laccopteris Woodwardi (Leckenby) Seward; Seward, p. 87.

Type . Leckenby's specimen, which originated from the Middle Jurassic near Scarborough, is stored in the Sedgwick

Museum, Cambridge, Specimen Number 126.


Material . Two specimens: OUM J.43276 and J.43279.

Description . Specimen J.43279 (Pl. 1, ®g. 2) is 8 mm long and 6´4 mm wide and has entire margins. The rachis is approximately 0´5 mm wide. The primary veins are opposite to subopposite, arise at about right-angles, and are spaced

0´8±0´9 mm apart. The primary veins divide into elongate meshes about half-way between the rachis and pinnule margin; the meshes are about 1´4 mm long. Near the pinnule margin, the secondary veins become non-anastomosed, simple or forking, and meet the pinnule margin at about right-angles. In some cases, there is an annular sorus in the centre of the large meshes near the rachis, about 0´1±0´2 mm in diameter. The number of sporangia in each sorus is dif®cult to make out but is probably about eight. The receptaculum in the centre of each sorus can be clearly seen, indicatingthat there was no indusium.

Specimen J.43276 (Pl. 1, ®g. 3) shows a segment 9 mm long and with a preserved width of 4´1 mm. The pinnule margin appears lobed, but this may be due to poor preservation. The rachis is 0´9 mm wide. Primary veins are opposite to subopposite given off at about right-angles, and are spaced 1´1±1´3 mm apart. There are annular structures between the primary veins, 1´0±1´2 mm in diameter. Some distance between the rachis and pinnule margin, secondary veins occur within the primary meshes, forminglower-order meshes.

Remarks . The Stones®eld specimens clearly belongto Phlebopteris due to the reticulate veins and the sori lackingan indusium. Although small, the specimens are morphologically similar to the Yorkshire examples of P. woodwardii ®gured by Harris (1961 a , ®g. 35). In particular, they show the vaulting of the lamina below the vein arches where sori would be positioned in fertile fronds, this beinga key character for distinguishing this species from P. polypodioides Brongniart, 1837. Harris noted that the

Yorkshire specimens are normally preserved as fusain fragments. He thus interpreted them as the remains of inland, `heath' plants that had been burned and then transported into the depositional areas of the river delta by ¯ood. However, the Stones®eld specimens do not appear to be preserved as fusain.

Seward (1904) assigned some fragments ®gured by Phillips (1871, pl. 28, ®gs 8±10) as Taeniopteris angusta Phillips to Leckenby's species. Although the specimens are very fragmentary, Harris (1961 a , p. 106) agreed with Seward's identi®cation, without comment. The more poorly preserved fragment occurs within a coarser matrix, suggesting deposition in a higher energy environment.

In his synonymy for this species, Seward (1904) listed a reference by De Zigno dated 1856, which would appear to pre-date Leckenby's (1864) use of the name. However, 1856 is the date of publication of part 1 of

De Zigno's study, whereas P. woodwardii is mentioned in a part dated 1867. A more complete account of the synonymy of P. woodwardii can be found in Harris (1961 a ).

Family

DICKSONIACEAE

Bower, 1908

Genus

CONIOPTERIS

Brongniart, 1849

Type species .

C. murrayana (Brongniart) Brongniart, 1849.

Remarks . The Dicksoniaceae is the commonest fern family found in the Yorkshire Jurassic and

Coniopteris is the commonest genus of that family there (Harris, 1961 a ). As pointed out by Harris,

EXPLANATION OF PLATE

1

Fig. 1. Cf.

Dictyophyllum sp., J.43275, fragment of a pinnati®d segment; ´ 2.

Figs 2±3.

Phlebopteris woodwardii Leckenby; ´ 5. 2, J.43279, leaf segment with anastomosed veining along outer margins, and a possible sorus on right-hand side of midvein. 3, J.43276, leaf segment with undulate margins, possibly due to poor preservation.

Figs 4±5. Cf.

Coniopteris sp. 4, J.54983, bipinnate segment with elongate, shallowly lobed pinnules; ´ 3. 5, J.1150, holotype of S. cysteoides Lindley and Hutton, with more deeply incised pinnules; ´ 2.

Figs 6±7. Cf.

Ctenozamites leckenbyi (Bean ex Leckenby) Nathorst. 6, J.1137, pinnae fragment with obliquely attached pinnules; ´ 2. 7, J.54974, terminal part of pinnae with part of terminal pinnule; ´ 3.

All specimens from the Stones®eld Slate, Stones®eld, Oxfordshire.

CLEAL and REES, Jurassic plants

P L A T E 1

746 P A L A E O N T O L O G Y , V O L U M E 4 6 there are nomenclatural problems surrounding Coniopteris , as it is almost certainly a later synonym of

Thyrsopteris Kunze (1834) and/or Tympanophora Lindley and Hutton (1835). However, this will need to be resolved in the context of a thorough revision of these ferns and this review of the poorly preserved

Stones®eld material is not the place to do it.

cf.

Coniopteris sp.

Plate 1, ®gures 4±5; Pl. 2, ®gure 1

} 1835 Sphenopteris cysteoides Lindley and Hutton, pl. 176a.

} 1871 Sphaenopteris plumosa Phillips, p. 168, diagram 28, ®gs 3±4.

} 1871 Pecopteris approximata Phillips, p. 168, diagram 28, ®g. 2.

} 1871 Pecopteris incisa Phillips ( non Sternberg, 1825), p. 168, diagram 28, ®gs 5±6.

} 1871 Sphenopteris cysteoõÈdes Lindley and Hutton; Phillips, p. 168, diagram 28, ®g. 7.

} 1904 Sphenopteris sp. a. Seward, p. 92.

} 1904 Sphenopteris sp. b. Seward, p. 93.

Material . Five specimens: OUM J.1150 (holotype of S. cysteoides ), J.43274, J.43311, J.54982 and J.54983.

Description . Small fragments of fronds, showing small, deeply incised pinnules, c.

2 mm long by 1 mm wide.

One of the specimens (J.43311) shows the rachis being strongly de¯ected at the attachment position of each pinnule. The preservation is very poor and details of the venation and the general outline of the pinnules are unclear.

Remarks . These fragmentary specimens are undoubtedly ferns, but their family and generic position is less certain. Seward (1904) compared them with Coniopteris hymenophylloides and C. quinqueloba

(Phillips) Seward (the latter is, according to Harris 1961 a , a later synonym of C. hymenophylloides ), but decided that the absence of fertile specimens made such an assignment unsafe. This reservation is understandable, but assigning them to that genus with a `cf.' is probably as safe an option as any. They certainly appear different from the other dicksoniacean genera known from the Yorkshire Jurassic,

Kylikipteris Harris, 1961 a , and Eboracia Thomas, 1911, which tend to have less divided pinnules. On the other hand, it must be remembered that such poorly preserved material cannot give unequivocal proof of the existence of the Dicksoniaceae at Stones®eld. There is, for instance, a possible comparison with the schizaeacean fern Stachypteris Pomel, 1849, which can only be reliably distinguished from

Coniopteris where fertile material is available (Thomas 1912; Harris 1961 a ). Seward himself referred to them as Sphenopteris spp., but this name is best restricted to foliage similar to that of its type

S. elegans Brongniart, 1822 (i.e. lagenostomalean fronds, mainly known from the Carboniferous; van

Amerom 1975).

As pointed out by Seward (1904), one of the names used by Phillips (1871) for this Stones®eld material

( Pecopteris incisa Phillips) is a later homonym of P. incisa Sternberg, 1825. According to Kidston (1925), the latter is probably a later synonym of Mariopteris muricata (Schlotheim) Zeiller, the frond of a lianescent gymnosperm (`pteridosperm') from the Upper Carboniferous of Europe.

EXPLANATION OF PLATE 2

Fig. 1. Cf.

Coniopteris sp., J.54982, bipinnate segment with deeply incised pinnules; ´ 2´5.

Fig. 2.

Sagenopteris colpodes Harris, V.4071, pair of attached lea¯ets; ´ 2.

Fig. 3.

Ctenis sp., J.42624, holotype of Ctenis latifolia (Brongniart) Seward, showing venation with occasional anastomoses; ´ 2.

Fig. 4.

Pelourdea megaphylla (Phillips) Seward, V.4652, small leaf with part of stem still attached at base of leaf; ´ 1.



P L A T E 2


Division

GYMNOSPERMOPHYTA

Class

UNNAMED

Order CAYTONIALES

Family

CAYTONIACEAE

Thomas,1925

Genus

SAGENOPTERIS

Presl, in Sternberg 1838 emend. Rees,1993 b

Lectotype species . Harris (1932) designated S. nilssoniana (Brongniart) Ward,1900 as the type species of

Sagenopteris . Technically,this is invalid,as ICBN Article 10.1 (Greuter et al.

2000) requires that a genus be typi®ed by a specimen described or referred to in the generic protologue; Presl referred to neither Brongniart's specimen nor his species epithet. Of the six species referred to in the protologue,four ( S. rhoifolia Presl, S. semicordata Presl,

S. acuminata Presl, S. diphylla Presl) are now regarded as conspeci®c with S. nilssoniana (KvacÏek and StrakovaÂ 1997).

KvacÏek and StrakovaÂ (1997) designated S. rhoifolia as the type of Sagenopteris ,but this proposal is also invalid. Under

ICBN Article 8.5 (Greuter et al.

2000) the type has to be a specimen and the holotype of S. rhoifolia has been lost. Of the other three Presl species regarded as synonyms of S. nilssoniana ,only S. acuminata has an extant type,and so this is proposed here as the lectotype species of Sagenopteris .

Sagenopteris colpodes Harris,1940 emend. Harris,1964

Plate 2,®gure 2

} 1904 Sagenopteris Phillipsi (Brongniart) Presl; Seward,p. 94,pl. 9,®g. 3.

*1940 Sagenopteris colpodes Harris,p. 250,text-®gs 1±2,6 F±H .

1964 Sagenopteris colpodes Harris,p. 4,text-®gs 1±3.

} 1998 Sagenopteris colpodes Harris; Cleal and Rees,pl. 1.

Holotype . NHM V.2641 (®gured Harris 1940,text-®g. 6 G ).

Material . Two specimens,NHM V.4071 and V.4667/4655 (part and counterpart).

Description . The most complete specimen (Pl. 2,®g. 2) shows two obovate lea¯ets joined at the base to a short petiole c.

1 mm long. The left-hand lea¯et has lost its distalmost margin but is otherwise complete; its preserved length is

30 mm,and the maximum width 13 mm. The right-hand lea¯et has also lost its apex,in addition to having lost part of its right-hand side and being longitudinally split. Both lea¯ets have a straight midvein extending for about half their length. Lateral veins are produced from the midvein at c.

5 8 ,arch broadly and meet lea¯et lateral margins at 60±80 8 .

The veins are dichotomous or occasionally anastomosed. There are 16±20 veins per cm along the margin in the middle of the lea¯et.

The second specimen (represented by part and counterpart) shows a single broken lea¯et with both the apex and proximal attachment missing. The venation consists of a midvein,and dichotomous or occasionally anastomosing lateral veins.

Remarks . Seward (1904) ®rst noted the two specimens of this species from Stones®eld. However,his illustration of the venation of the more complete of the two is a little misleading as it fails to show that the laterals occasionally anastomose,and suggests that they meet the lea¯et margin at a much lower angle.

Seward (1904) referred them to Sagenopteris phillipsii ,which at that time was the only welldocumented species of the genus from Yorkshire. However,Harris (1940) revised the taxonomy of the

Yorkshire fossils,recognizing two discrete species, S. phillipsii and S. colpodes . Harris (1964) also noted that two distinct morphologies were recognizable within what he called S. colpodes ,a large and a small form. The more complete of the two Stones®eld specimens is identical in shape to the small morphotype of

S. colpodes . There are obviously no cuticles to corroborate its identi®cation,but we can ®nd no other species with which it compares so well morphologically.

Order

PELTASPERMALES

Family CORYSTOSPERMACEAE

Genus CTENOZAMITES Nathorst,1886,emend. Harris,1964

Type species .

Ctenozamites cycadea (Berger) Schenk,1887 (type ®gured by Berger 1832,pl. 3,®g. 2) was designated by Harris (1964). In the protologue of this genus,Nathorst (1886) referred to this species as C. bergeri (GoÈppert),based

C L E A L A N D R E E S : M I D D L E J U R A S S I C F L O R A 749 on ` Odontopteris ' bergeri GoÈppert, 1836. However, the latter is a later nomenclatural synonym of ` Odontopteris ' cycadea Berger, 1832and must, therefore, be suppressed.

Remarks.

At ®rst glance, the fossils assigned to this morphogenus are typical cycadophyte fronds, belonging either to cycads or bennettitaleans. However, Schenk (1887) and Harris (1961 b ) have shown that there is sometimes (but not always) a bifurcation of the primary rachis, which is a feature not normally associated with either cycads or bennettitaleans (see also Schweitzer and Kirchner 1998). Furthermore, fronds of the very similar morphogenus Ptilozamites Nathorst have been linked with the corystosperm pollen-bearing organ Harrisothecium Lundblad, 1961, which is quite unlike the male organs of cycads or bennettitaleans (Lundblad 1950; Harris 1961 b , 1964). We have, therefore, also provisionally placed

Ctenozamites in the Corystospermaceae.

cf.

Ctenozamites leckenbyi (Bean ex Leckenby) Nathorst, 1886 emend. Harris, 1964


Material.

Two specimens; OUM J.1137 and J.54974.

Description.

The larger specimen (Pl. 1, ®g. 6) is a near-terminal fragment of a pinnate segment, 25 mm long and up to

13 mm wide. The fragment tapers distally but the terminal part is missing. Lea¯ets are suboppositely or alternately arranged along the rachis, obliquely attached at c.

45 8 . The largest lea¯et is 8 mm long and 4 mm wide, parallel-sided in its proximal part, but tapering distally to a bluntly acuminate apex. They are broadly attached to the rachis, sometimes showing a slight acroscopic constriction.

The second specimen (Pl. 1, ®g. 7) is from nearer the apex of the frond and preserves part of the apical pinnule. The fragment is 15 mm long and 8 mm wide, with obliquely attached lea¯ets alternately arranged along the rachis. The largest lea¯et is 6 mm long and 3 mm wide, parallel-sided in its proximal part, but tapering distally to a bluntly acuminate apex. They are broadly attached to the rachis. In both specimens, the venation is unclear but there is no evidence of a prominent midvein.

Remarks.

Harris examined one of these fragments and left a note suggesting that it was C. leckenbyi .

He also mentioned it brie¯y in the second volume of his Yorkshire monograph (Harris 1964, p. 93). It has much smaller lea¯ets than normally seen in this species. However, this may be simply because it is from near the end of a frond and there is some comparison with another near-terminal fragment ®gured by Harris (1964, text-®g. 39

E

). The second fragment is equally poor but seems to show similar-shaped lea¯ets.

There is some comparison in lea¯et shape with Pachypteris papillosa (Thomas and Bose) Harris or even

P. lanceolata Brongniart, such as ®gured from the Yorkshire Jurassic by Harris (1964). However, they do not show the distinct midvein that normally occurs in these fronds. On balance, we have decided to follow

Harris's opinion, although in view of the fragmentary nature of the specimens we have assigned them to

C. leckenbyi with a `cf.'.

Genus PACHYPTERIS Brongniart, 1828 a emend. Harris, 1964

Type species .

Pachypteris lanceolata Brongniart, 1829.

Remarks.

This is a tightly circumscribed morphogenus, with distinctive morphological and cuticular characters (Harris 1964; Barale 1971, 1981). Harris (1964) argued that there is repeated association in the Yorkshire Jurassic between Pachypteris papillosa (Thomas and Bose) Harris and the corystospermacean pollen organ Pteroma thomasii Harris. Kirchner and MuÈller (1992) have also shown that

Pachypteris rhomboidalis (Ettingshausen) Nathorst has similar epidermal features to the corystospermacean reproductive organs Umkomasia franconica Kirchner and MuÈller ( , ) and Pteruchus septentrionalis Kirchner and MuÈller ( < ). There seems little doubt, therefore, that Pachypteris represents corystospermacean foliage.


Pachypteris macrophylla (Brongniart) comb. nov.

Plate 13, ®gure 2; Plate 14, ®gure 2

} 1828 a Sphenopteris ?

macrophylla Brongniart, p. 51 (name only).

} 1828 a Taxites podocarpoides Brongniart, p. 108 (name only).

T } 1831 Sphenopteris ?

macrophylla Brongniart, p. 212, pl. 58, ®g. 3.

1836 Hymenophyllites macrophylla (Brongniart) GoÈppert, p. 262.

} 1849 Hymenophyllites macrophyllus (Brongniart) GoÈppert; Brongniart, p. 105.

} 1849 Taxites podocarpoides Brongniart; Brongniart, p. 106.

?1867

Hymenophyllites macrophylla (Brongniart) GoÈppert; De Zigno, p. 87.

} 1871 Hymenophyllites macrophylla (Brongniart) GoÈppert; Phillips, p. 168.

} 1871 Taxites podocarpoides Brongniart; Phillips, p. 171, diagram 31, ®g. 6.

} ?1871

`Ramose plant.

Tax. podoc.

' Phillips, diagram 30, ®g. 7.

Holotype . The specimen from Stones®eld ®gured by Brongniart (1831, pl. 58, ®g. 3) and photographically re®gured here on Plate 14, ®gure 2; OUM J.43273.

Emended diagnosis . Bipinnate frond, at least 60mm wide, with primary rachis 3±4 mm wide. Ultimate pinnae oppositely or suboppositely attached to primary rachis at c.

45 8 , and spaced at 10±25 mm intervals.

Rachis of ultimate pinnae 1±2 mm wide, bearing linear or slightly spathulate pinnules, up to 15 mm long and 1´5±2´0mm (rarely 3 mm) wide. Pinnules attached at 25±30 8 to rachis, non-decurrent at base, spaced at 5±10mm intervals. Single vein extends along length of each pinnule.

Material . In addition to the holotype, there two other OUM specimens: J.29748 (the type of Taxites podocarpoides

Brongniart) and J.43291.

Description.

The specimen shown on Plate 13, ®gure 2 consists of a bipinnate fragment that was originally 60mm wide and is preserved for a length of 60mm. The primary rachis is 4 mm wide in its proximal part, tapering distally to 3 mm wide. Parts of ®ve pinnae are attached to the left-hand side of the primary rachis at intervals of 10±15 mm. On the right-hand side, there is just one complete pinna attached, the stump of the rachis of a second pinna, and part of a third pinna that probably lies in its original position although the attachment is not preserved. The pinnae are only very slightly offset from an opposite arrangement along the primary rachis, and are inserted at c.

45 8 .

The most completely preserved ultimate pinna has a preserved length of 40mm and only seems to lack a small part of the elongate-linear terminal pinnule. The lateral pinnules are attached at c.

30 8 at intervals of 5±8 mm. In none of the preserved pinnae is it possible to determine if the pinnules are arranged oppositely or alternately. The pinnules are elongate-linear and up to 15 mm long and 2 mm wide. The venation is not clearly visible other than for a prominent midvein that extends the length of the pinnules.

The holotype (Pl. 14, ®g. 2) is 75 mm long and originally represented a foliar fragment 55 mm wide. The primary rachis is 3 mm wide. On the left side of the specimen, just one ultimate pinna is attached, and there are the remains of what might be another detached pinna. On the right-hand side, there are parts of two pinnae, and part of a third pinna that would have been attached below the preserved part of the primary pinna. The pinnae appear to be preserved in a near-opposite arrangement. The angle of attachment is dif®cult to con®rm, but appears to be 30±45 8 .

None of the pinnae is complete. They bear elongate-linear pinnules at 25±30 8 . The only complete pinnule is 18 mm long and 2 mm wide, and has a midvein extending along its length. One pinnule on the same pinna appears to be slightly spathulate.

Remarks.

Brongniart (1849) regarded the lectotype of Pachypteris desmomera (de Saporta) Barale (from the lithographic limestones at Morestel, near Lyon) as conspeci®c with what he then called Hymenophyllites macrophyllus from Stones®eld. De Saporta (1873) had distinguished them because the French specimen has pinnae and pinnules that are oppositely arranged. He believed the Stones®eld specimen

(which he erroneously stated as originating from Yorkshire) to have, in contrast, alternately arranged pinnae and pinnules. However, this is mainly a result of Brongniart's (1831) somewhat diagrammatic illustration and the actual specimen shows an opposite or subopposite arrangement, as does the other OUM specimen (J.43291).

Most authors have agreed with Brongniart and regarded the two species as conspeci®c, at least with a

C L E A L A N D R E E S : M I D D L E J U R A S S I C F L O R A 751 query (Seward 1904; Harris 1964; Barale 1981). However, the preserved leaf width and the size of the pinnules of P. desmomera suggests that its fronds were normally much larger than in the Stones®eld specimens. Also, we do not know the epidermal structure of the latter, whereas it has been well documented for P. desmomera (e.g. Barale 1971, 1981), and so it is impossible to compare them anatomically. In our view, it is wiser to keep the two as separate species, at least until more can be found out about Brongniart's Stones®eld species.

In view of the similarities between the Stones®eld specimens and P. desmomera , we believe that the former is also a Pachypteris and thus propose the new combination, Pachypteris macrophylla .

Genus KOMLOPTERIS Barbacka, 1994

Type species .

Komlopteris nordenskioeldii (Nathorst) Barbacka.

Remarks.

This morphogenus was established for certain species that had traditionally been assigned to

Thinnfeldia Ettingshausen, 1852. It was recognized shortly after the ®rst publication of Thinnfeldia that its type was probably a Pachypteris Brongniart, 1828 b and was thus a later taxonomic synonym of the latter

(AndraÈ 1855).

Thinnfeldia nevertheless continued to be widely used in the literature, albeit surrounded by taxonomic and nomenclatural confusion (for more in depth discussions, see Doludenko 1971; Barbacka

1993; Popa 1997; Doludenko et al . 1998).

Barbacka (1994) attempted to overcome the problem by proposing a new name Komlopteris as a morphogenus for certain species previously assigned to Thinnfeldia .

Komlopteris was described as having exclusively once-pinnate fronds, and pinnules that are entire-margined and mostly more than 30 mm long and 10 mm wide.

Pachypteris , in contrast can have once- or twice-pinnate fronds, and the pinnules are often dissected and usually less than 30 mm long and 10 mm wide. Barbacka (1994) also noted that the stomata in Komlopteris occur in marked intercostal bands on the pinnules and there is not the marked cuticular thickening around the pore, as seen in Pachypteris .

Komlopteris speciosa (Ettingshausen) comb. nov.


*1852 Thinnfeldia speciosa Ettingshausen, p. 4, pl. 1, ®g. 8.

1867 Thinnfeldia speciosa Ettingshausen; Schenk, p. 115 (description only).

} 1904 Cf.

Thinnfeldia speciosa Ettingshausen; Seward, p. 95, pl. 10, ®gs 1±3.

1912 Thinnfeldia speciosa Ettingshausen; Gothan, p. 69, pl. 13, ®g. 1 (copy of Ettingshausen's illustration).

1914 Thinnfeldia speciosa Ettingshausen; Antevs, p. 33, pl. 4, ®g. 2 (copy of Ettingshausen's illustration).

Neotype . The holotype ®gured by Ettingshausen (1852, pl. 1, ®g. 8) originated from the Lower Jurassic Anina ¯ora,

Romania. According to Popa (1997), this specimen has been lost, probably during World War II. Popa has therefore designated as neotype leaf fragment number 1 on specimen P41/C2/S6/E16, stored in the collections of the Department of Geology and Palaeontology, University of Bucharest. There are also ten cuticle slides prepared from this specimen

(numbers 100±110). The specimen was collected from `the pizza with plant bed' in the Valea Tereziei Member

(Hettangian Stage), Ponor Quarry, near Anina, Romania.

Material.

Three specimens: NHM V.3422 and V.4074, and OUM J.43277.

Description.

The fronds appear to be once-pinnate, of unknown length, but reaching a width of at least 45 mm. The apical pinnule is robust and lanceolate, 46 mm long and 12 mm wide, and has an undulate margin (Pl. 13, ®g. 3).

Lateral pinnules are inserted at 25±35 8 on the rachis, and are suboppositely arranged. Lateral pinnule spacing varies from c.

8 mm in the apical part of the frond to at least 15 mm lower down. Lateral pinnules 4±5 mm wide, but varying inlength from c.

30 mm near the frond apex to at least 47 mm long lower down. In the distal part of the frond, the pinnules are slightly barrel-shaped with a bluntly acuminate apex (Pl. 13, ®g. 3). Lower down, they are more parallelsided for most of their length, tapering in their distal part to what seems like a sharply acute apex, although the preservation is too poor to be certain (Pl. 15, ®g. 1). At the base the pinnules are decurrent and sometimes slightly constricted.

7 52 P A L A E O N T O L O G Y , V O L U M E 4 6

A strong midvein extends along the middle of the pinnules. Lateral veins are only faintly preserved, but are simple, straight and oblique to the pinnule margin.

Remarks.

The most recent account of this species has been by Popa (1997), who illustrated additional specimens from the type area (Anina Mountains, Romania). Popa retained the species in Thinnfeldia , which he regarded as being intermediate between Pachypteris and Komlopteris . However, Popa (pers.

comm. 2001) now agrees that Thinnfeldia must be regarded as a later synonym of Pachypteris and thus suppressed. Popa (1997, table 1) gave a detailed morphological and epidermal comparison between

` Thinnfeldia ' speciosa , and the types of both Pachypteris and Komlopteris . The stomata in Ettingshausen's species are hypoamphistomatic, whereas Pachypteris is hypostomatic and Komlopteris is amphistomatic.

However, in all other characters ` T.

' speciosa clearly lies closest to Komlopteris (leaf and pinnule morphology, venation, stomatal distribution, form of subsidiary cells). We therefore propose that

Ettingshausen's species should be transferred to Komlopteris .

Harris (1964) suggested that the holotype of K. speciosa was a detached part of a bipinnate leaf. We can see no reason for making such a suggestion and reject it. Harris (1964) also suggested that the Stones®eld specimens probably belong to Pachypteris papillosa (Thomas and Bose) Harris. However, the former has a much more robust apical pinnule, and more slender, elongated lateral pinnules than P. papillosa . Only the pinnules from the apical parts of smaller leaves of P. papillosa (e.g. Harris 1964, text-®g. 52 A , E ) are similarly elongate to K. speciosa , the more typical ones (e.g. Harris 1964, text-®g. 53

D

) being far more robust.

Seward (1904) assigned the Stones®eld specimens (plus others from Eyeford) to this species with a `cf.', due to their fragmentary nature. However, Antevs (1914) had no doubt that they belonged to

Ettingshausen's species, a view with which we concur. An added complication is that Seward (1904) included a range of bipinnate frond segments in this species, which more probably belong to Pachypteris macrophylla (Brongniart) comb. nov.

` CYCADOPHYTES '

Remarks.

Foliage resembling that of modern-day cycads has presented palaeobotanists with major problems, especially when dealing with foliage lacking cuticles. Although the Bennettitales and Cycadales were quite different biologically (Harris, 1964, 1969 a ) their leaves (as well as those of the Pentoxylales) are often very similar macroscopically. In some cases, it is possible to make a reasonable conjecture based on a comparison of gross morphology with more completely preserved fossils. This is in many ways no different from assigning a fern impression to a particular genus and family in the absence of fertile pinnules. In other cases, however, such a comparison does not help, as either the comparison is too tenuous or the particular type of bennettite/cycad foliage just cannot be separated on gross morphology. An example of the latter problem is foliage of the Nilssonia / Nilssoniopteris type, which cannot reliably be distinguished on morphology alone. The veins of Nilssonia are always simple but in Nilssoniopteris they are often (but not always) forked. The midvein in Nilssonia is normally covered by lamina and so is only visible on the lower surface. In Nilssoniopteris , the lamina is more laterally attached to the midvein so that the latter can normally be seen on the upper leaf surface. As pointed out by Harris (1969), however, some slender leaves of

Nilssoniopteris have mainly simple veins and a midvein that is all but invisible on the upper surface. The


Fig. 1.

Ctenis cf.

sulcicaulis (Phillips) Ward, J.43325, fragment of large frond with elongate pinnules that have anastomosed veins and a decurrent basiciopic margin; ´ 0´5.

Figs 2±4.

Ptilophyllum pectiniformis (Sternberg) comb. nov. 2, BMNH 40693; large, decurrent pinnules; ´ 2. 3,

J.43290, fragment of frond with small pinnules, gently tapering towards frond apex; ´ 1´5. 4, J.21796, holotype, fragment of frond with larger pinnules, frond tapering more markedly towards apex; ´ 1´5.


CLEAL and REES, Ctenis , Ptilophyllum

P L A T E 3

754 P A L A E O N T O L O G Y , V O L U M E 4 6 problem is epitomized by the Stones®eld specimens (Pl. 7, ®gs 1±2) that show simple veins and a prominent midvein on what appears to be the upper leaf surface. We have, therefore, proposed that a third morphogenus should be used ( Taeniopteris ) for fossils lacking cuticles. The case for doing this is argued out more completely later.

Class

CYCADOPSIDA

Order CYCADALES

Family

UNKNOWN

Genus

CTENIS

Lindley and Hutton, 1834 emend. Harris, 1964

Lectotype species .

Ctenis sulcicaulis (Phillips) Ward (basionym Cycadites sulcicaulis Phillips, 1829), designated by

Harris (1964).

Ctenis cf.

sulcicaulis (Phillips) Ward, 1905

Plate 3, ®gure 1

Material . OUM J.43325.

Description . The specimen represents part of a frond, preserved for a length of 160 mm. The rachis is 3 mm wide and bears ®ve long pinnae on the left side and a single pinna on the right, all attached at c.

75 8 . The pinnae are suboppositely arranged and spaced at 25 mm intervals. None of the pinnae is complete, but the most proximal seems to have only lost its apex and was probably originally c.

110 mm long. The adjacent pinna has lost a little more of the apex, but is estimated to have been originally 120±130 mm long. The pinnae are parallel-sided for most of their proximal part but taper in the distal half; they are 12±14 mm wide half-way along the length of the pinna. The acroscopic margin of the pinnae is straight, the basiscopic margin strongly decurrent. The venation is poorly preserved, but some evidence of parallel veins with occasional anastomoses can be seen.

Remarks.

In view of the presence of vein anastomoses, we have little doubt that this is a cycad of the genus

Ctenis . It agrees closely in size and shape with the better-preserved examples of C. sulcicaulis from

Yorkshire ®gured by Harris (1964, text-®gs 44, 46

C

). If it had been found at somewhere like Gristhorpe, it would probably have been assigned to that species without a query. However, the fact that the venation is not perfectly preserved, and there is no evidence of cuticles, has caused us to be more cautious. This is particularly in view of the existence of species from other ¯oras (e.g.

Ctenis minuta Florin, 1933 from the

Rhaetic of Sweden and Greenland) that are very similar in shape to C. sulcicaulis but differ in epidermal features.

Similar specimens have recently been described from the Middle Jurassic of Iran by Schweitzer and

Kirchner (1998) as Ctenis sp. cf.

C. sulcicaulis . These fronds have pinnae with a very similar venation to the Stones®eld specimens, but which are somewhat wider (20±30 mm).

Ctenis sp.

Plate 2, ®gure 3

} 1833 Taeniopteris latifolia Brongniart, p. 266, pl. 82, ®g. 6.

} 1904 Ctenis latifolia (Brongniart) Seward, p. 115.

For a full synonymy of this species, see Seward (1904).

Material.

OUM J.42624.

Description.

The specimen shows a short pinna fragment 40 mm long. The rachis is 2 mm wide and bears short pinnae, two on the left side and three on the right, in an alternate arrangement. The pinnae are subtriangular, the proximal two

20 mm long and 18 mm wide, the next one 30 mm long and 12 mm wide; the distal two pinnae are incomplete. The acroscopic margin of the pinnae mostly run straight to the rachis, while the basiscopic margin is usually decurrent.

C L E A L A N D R E E S : M I D D L E J U R A S S I C F L O R A 755

Eleven prominent, more or less parallel veins run along the proximal part of the pinnae and show clear but widely spaced anastomoses.

Remarks.

This specimen is the holotype of Ctenis latifolia (Brongniart) Seward. However, it is a poor fragment, clearly representing the basal part of a frond, which does not show the shape of the fully developed pinnae. It is thus totally inadequate as the basis of de®ning a species and so the name is rejected.

The venation nevertheless clearly indicates that it is from the cycad frond Ctenis . It is thus tempting to regard it as the basal part of a frond of the same species as the previous specimen, described as C . cf.

sulcicaulis . However, Harris (1964) has reported the basal part of the C. sulcicaulis frond to have short, spine-like pinnae, quite different from the squat, subtriangular pinnae in the Stones®eld specimen.

Thus, either there is a single Ctenis species here, which is different from C. sulcicaulis ; or there are two species, one of which is C. sulcicaulis . The matter clearly cannot be resolved on the available material, and we have adopted a conservative approach of keeping the specimens taxonomically separate.

Hill (1987) reported areas of necrosis on this specimen, comparing it with similar damage in marattialean foliage from the Yorkshire Jurassic.

Class

GNETOPSIDA

Order BENNETTITALES

Family

UNKNOWN

Genus PTILOPHYLLUM Morris, 1840

Type species .

Ptilophyllum acutifolium Morris, 1840.

Remarks.

The background to this morphogenus has been reviewed by Harris (1969 a ). He distinguished it from both Otozamites and Zamites because the basiscopic angle of its pinnae is decurrent rather than constricted (see also Table 1). It is a highly distinctive form of bennettite foliage, with no known cycad having comparable fronds. Consequently, although the Stones®eld specimens do not reveal any evidence of epidermal anatomy, they have been placed unequivocally within the Bennettitales.

Ptilophyllum pectiniformis (Sternberg) comb. nov.

Plate 3, ®gures 2±4; Plate 4, ®gures 1±2

* } 1823 Polypodiolites pectiniformis Sternberg, p. 36, pl. 33, ®g. 1.

} 1823 Fucoides (Caulerpa) pennatula Brongniart, p. 301, pl. 21, ®g. 3.

} 1828 a Zamia pectinata Brongniart, p. 49.

} 1835 Zamia pectinata Brongniart; Lindley and Hutton, p. 61, pl. 172.

} 1835 Zamia taxina Lindley and Hutton, p. 67, pl. 175.

} 1871 Palaeozamia pectinata (Brongniart) Phillips, p. 169, diagram 30, ®gs 2±3.

} 1871 Palaeozamia taxina (Lindley and Hutton) Phillips, p. 169, diagram 30, ®gs 4±5.

} 1904 Williamsonia pecten (Phillips) Seward, p. 106, pl. 9, ®g. 6; pl. 12, ®g. 8.

} T1917 Ptilophyllum pecten (Phillips) Morris; Seward, p. 523, text-®g. 595 (photograph of holotype).

} 1998 Ptilophyllum pectinoides (Phillips) Morris; Cleal and Rees ( non Phillips), pl. 8.

Holotype . OUM J.21796 (Pl. 3, ®g. 4), from Stones®eld.

Material.

There are 12 NHM specimens: 40693, 40694, 41377a/b, V. 84 (ex Egerton Collection), V. 1021, V.1022a/b

(ex J. E. Lee Collection), V.3361 (®gured by Seward 1904, pl. 9, ®g. 6), V.3521, V.4659, V.4664, V. 4668 and V.9428/

9. There are a further 12 OUM specimens: J.1147, J.1147a, J.1148 (three syntypes of Zamia taxina ), J.1154 (holotype of Zamia pectinata Brongniart ex Lindley and Hutton), J.43280, J.43289, J.43292, J.43294, J.43316, J.43318, J.43319, plus the holotype (see above). A single specimen is in Willoughby Hall Museum, Nottingham: FS 06622.

Description.

Leaf once pinnate. Pinnae attached to upper surface of rachis at 50±75 8 (typically 60±65 8 ), decreasing to

40 8 near leaf apex. Only broken leaves are known, the most complete being 41 mm wide and 220 mm long (Pl. 4, ®g. 1).


TABLE

1. Pinna characteristics in Zamites , Otozamites and Ptilophyllum (modi®ed from Person and Delevoryas 1982 and Gee 1989).

Acroscopic basal margin

Basiscopic basal margin

Curvature of acroscopic veins

Curvature of basiscopic veins

Symmetry of pinna base

Presence of auricle

Zamites

Typically contracted

Typically contracted

Basipetal

Acropetal

Typically symmetrical

Typically absent

Otozamites

Contracted

Contracted

Acropetal

Acropetal

Asymmetrical

On acroscopic margin

Ptilophyllum

Contracted

Decurrent

Basipetal

Basipetal

Asymmetrical

Typically absent

Leaves typically parallel-sided for much of their length (Pl. 4, ®gs 1±2) but taper gently towards the apex (Pl. 3, ®gs

3±4). Pinnae are typically alternate, occasionally subopposite. Pinna margins are parallel or subparallel for 55±85 per cent of pinna length before converging towards the apex. Pinnae 7±19 mm long (typically 11±15 mm), 1´5±3 mm wide. Length:width ratio of pinna 3´5:1 to 8:1 (typically c . 6:1). Pinna apices are typically acute, occasionally subacute or obtuse. Pinna bases decurrent on rachis (Pl. 3, ®g. 2). Venation often indistinct, veins subparallel, diverging slightly towards pinna apices. Vein density (measured in central region of pinna) 4±9 per mm, c.

10±15 veins per pinna.

Remarks.

Harris (1969 a ) commented on the similarity between the Stones®eld species and the betterpreserved Ptilophyllum pectinoides (Phillips) Morris from the Yorkshire Jurassic. He recommended that the Stones®eld material should be referred to as P . sp. cf.

pectinoides . However, this ignores the fact that there is a perfectly legitimately published name based on the Stones®eld specimens, viz.

P. pectiniformis

(Sternberg). This cannot merely be regarded as an orthographic variant of the Yorkshire species name, as

Phillips (1829) made no reference to the Sternberg (1823) description; the similarity in the name merely re¯ects the similar, `comb'-like form of these leaves.

In essence, we are using P. pectiniformis for P. pectinoides -like foliage for which cuticles are not available. Some might consider it unwise to `clutter' the taxonomic literature with a second name for what is in effect poorly preserved material, but we cannot just ignore the Sternberg species because we do not like it.

It is validly published with a good type, and there can be little doubt that it is the same as the rest of the

Stones®eld fossils of this type. The alternative would be to say that the Stones®eld and Yorkshire material are conspeci®c, despite the epidermal structure of the former being unknown. This would clearly be unwise, as Harris (1969 a ) showed that epidermal characters are important for distinguishing species of Ptilophyllum .

Furthermore, it would mean that P. pectinoides would have to be suppressed in favour of P. pectiniformis , the latter having chronological priority. Such a proposal would be unlikely to meet with widespread favour among palaeobotanists as it in effect replaces a tightly de®ned taxon with a loosely de®ned taxon for what are essentially nomenclatural reasons. In our view, the best way to maintain taxonomic stability is to keep the two separate names for fossils of this type that are with and without cuticles.

Ptilophyllum cf.

hirsutum Thomas and Bancroft ex Harris, 1949

Plate 4, ®gure 3

Material.

OUM J.43323.


Figs 1±2.

Ptilophyllum pectiniformis (Sternberg) comb. nov. 1, J.1154, holotype of Zamia pectinata Brongniart ex

Lindley and Hutton, largest known leaf fragment; ´ 0´7. 2, V.3361, pinna fragment showing traces of venation;

´ 1´5.

Fig. 3.

Ptilophyllum cf.

hirsutum Thomas and Bancroft ex Harris, J.43323; ´ 1´25.


CLEAL and REES, Ptilophyllum

P L A T E 4


Description.

A single leaf fragment preserved for a length of 140 mm. The pinnae on only one side of the rachis are more or less fully preserved, but from these the leaf width can be estimated to have been 40 mm. The pinnae are alternately or suboppositely attached at about 70 8 to the rachis. The pinnae are 6±7 mm wide, straight for most of the length, but tapering in their distal one-third to a sharp apex. The basiscopic angle is decurrent, the acroscopic angle slightly constricted. The faint impression of parallel veins can be seen along the pinnae, but details of the venation are obscure.

Remarks.

This one specimen has all of the morphological characteristics of Ptilophyllum but has much broader, more robust pinnae than the common form of that genus found at Stones®eld, P. pectiniformis . A much closer comparison is with Ptilophyllum hirsutum Harris, 1949, from the Yorkshire Jurassic, with which it agrees in all observable morphological characters. However, as there is only one specimen from

Stones®eld and there is no evidence of cuticles, we feel it best to assign it to that species with a `cf.'.

There are nomenclatural dif®culties surrounding this species. Thomas and Bancroft (1913, p. 183) gave in a footnote to their Ptilophyllum sp. that it was a species that ` . . . will later be described as Ptilophyllum hirsutum . . . '. This clearly cannot be regarded as a valid publication of the species (ICBN, Article 34.1).

Seward (1917, p. 520) also mentioned the name, but only as one that had been `proposed', and he gave neither diagnosis nor type. The earliest effectively published diagnosis is by Harris (1949) and this must be regarded where the species is ®rst validly published. Harris (1949, 1969) did not mention a type specimen.

However, Thomas and Bancroft (1913) referred to a specimen from Marske Quarry ®gured by Thomas

(1913, text-®g. 3 B ) as showing a ` . . . typical outline of a frond . . . ' of this species. This specimen is therefore proposed here as the type.

Genus SPHENOZAMITES (Brongniart) Miquel, 1851 emend. Wesley, 1958

Type species .

Sphenozamites beanii (Lindley and Hutton) Miquel, 1851, designated by Brongniart (1849).

Remarks. Sphenozamites was originally established by Brongniart (1849, p. 61) as a section of Otozamites .

It was distinguished from the type section of that genus by the absence of a basal auricle on the lea¯ets. He suggested that it might eventually merit being raised in rank to genus and Miquel (1851) later did this. De

Saporta (1875, p. 183) revised the morphogenus, emending the diagnosis so that it was compatible with certain fronds with large pinnae (now known to be bennettitalean) from the French Jurassic. Fronds with broadly similar large pinnae were also described by de Zigno (1881) from the Grey Limestones of Veneto, northern Italy. It has been in this sense that most authors have accepted the genus. The most complete account has been by Wesley (1958), who revised the diagnosis to make Sphenozamites more clearly separated from the other morphogenera of bennettitalean fronds. According to Wesley, the main distinguishing characters are that the pinnae are (1) constricted both acroscopically and basiscopically,

(2) do not have an acroscopic auricle, and (3) are attached laterally to the rachis.

As pointed out by Seward (1904), however, there is a nomenclatural problem with such an interpretation of Sphenozamites as the type clearly belongs to Otozamites (see also Harris 1969 a ). A strict application of the nomenclatural rules would thus require the name Sphenozamites to be suppressed and another generic name found for the fossils described by de Saporta, De Zigno, and Wesley. Alternatively, the usually accepted concept of Sphenozamites could be retained by conserving it with an alternative type, such as one of the species described by de Saporta (1875) or De Zigno (1881). Wesley (1958) in effect did this when he revised Sphenozamites based mainly on observations on S. rossii De Zigno, but the move has not been formalized. Wesley's revision is nevertheless the preferred option and we have followed it here.


Fig. 1.

Sphenozamites bellii Seward, V.4069, single lea¯et showing broad basal attachment; ´ 1´5.

Figs 2, 4. ?

Weltrichia sp., part and counterpart of a single ray from a bennettite ¯ower; ´ 2. 2, V.4657; 4, V.4656.

Fig. 3.

Pelourdea megaphylla (Phillips) Seward, V.4652, close-up of leaf shown in Plate 2, ®gure 4, showing part of stem still attached at base; ´ 5.



P L A T E 5


Linnel (1932) had earlier tried to revise Sphenozamites based on Triassic specimens from Germany known as S. tener Compter. As pointed out by Wesley (1958), however, this species differs signi®cantly from Sphenozamites (as he and most other authors have interpreted it) in that the pinnae are oppositely arranged and attached towards the upper side of the rachis, and the frond is terminated by a single terminal pinnule. In addition, as pointed out by Linnel, the cuticles show a cycad-like epidermal structure, whereas the other species where epidermal structure is known are bennettitalean. For this reason, Wesley (1958) proposed the alternative name Apoldia tenera (Compter) Wesley for these Triassic fronds. If Linnel had formally proposed that this Triassic species should be regarded as the type of Sphenozamites then there might have been a case for accepting his interpretation. However, he did not and so we feel that it is legitimate to keep with Wesley's interpretation of the genus.

Sphenozamites bellii Seward, 1904


} 1871 Naiadea obtusa Buckman; Phillips, p. 169.

* } 1904 Sphenozamites Belli Seward, p. 119, pl. 11, ®g. 4.

} 1998 Sphenozamites bellii Seward; Cleal and Rees, pl. 3.

Holotype . OUM J.38471 (Pl. 6, ®g. 1), collected from Stones®eld by A. M. Bell.

Material.

Six specimens. In addition to the holotype, there is a second, unnumbered specimen in the OUM. There are also four NHM specimens: V.4069 (Pl. 5, ®g. 1) and its counterpart V.4642, 41381 and 52817.

Description.

Isolated lea¯ets, 70±90 mm long and 40±45 mm wide at their broadest part. They are subovate, tending sometimes to subfalcate, with a more or less pointed apex and a constricted base; the widest part is about a quarter of the way up the lea¯et from the base. They are attached to the rachis by a width of about 10 mm of the lea¯et. The lea¯et base is asymmetrical but never auriculate. Numerous veins enter the lea¯et at the base, and radiate out and occasionally dichotomize. On what is presumed to be the acroscopic side, the basalmost vein lies more or less parallel to the forward-extending margin of the lea¯et (Pl. 6, ®g. 1).

Remarks.

This species is only known from Stones®eld and Eyeford. Stones®eld material was ®rst recorded by Phillips (1871) as Naiadea obtusa Buckman ( in Brodie and Buckman 1845). Buckman's species may well be the same as N. obtusa , but the original illustration is poor and the specimen has not been available for study. It was for this reason alone that Seward (1904) decided to assign the Stones®eld material to a new species.

Although it is only known from isolated lea¯ets without cuticular evidence, Wesley (1958, p. 26) regarded the Stones®eld specimens as a `valid species of Sphenozamites' . In particular, he noted that the basalmost acroscopic veins lie parallel to the lea¯et margin, which indicates that there was no auricle at the base.

Family WILLIAMSONIACEAE

Genus WELTRICHIA Braun, 1849 emend. Harris, 1969 a

Type species .

Weltrichia mirabilis Braun, 1849.


Fig. 1.

Sphenozamites bellii Seward, J.38471, single lea¯et showing constricted basal attachment; ´ 1´5.

Fig. 2.

Pelourdea megaphylla (Phillips) Seward, J.42625, largest known leaf, clearly showing concave abscission zone at base; ´ 0´5.

Both specimens from the Stones®eld Slate, Stones®eld, Oxfordshire.

CLEAL and REES, Pelourdea , Sphenozamites

P L A T E 6


Remarks.

We follow Harris (1969 a ) in his interpretation of this morphogenus as male bennettitalean reproductive organs.

?

Weltrichia sp.

Plate 5,®gures 2,4

} 1998 ?

Weltrichia sp. Cleal and Rees,pl. 5.

Material.

Part and counterpart of a single fragment: NHM V.4656 and V.4657.

Description.

The fossil resembles the ray of a male bennettitalean ¯ower,preserved in lateral view. The ray is cuneate,

36 mm long,20 mm wide at its distal end,tapering to 3 mm wide proximally. The distal margin is incised with bluntly pointed teeth. The incisions extend for up to 6 mm into the lamina. The surface of the distal third of the ¯ower is covered with dense longitudinal striae. This part of the ¯ower gives the impression that the `sporophyll' was made of thick tissue. The part specimen (Pl. 5,®g. 2) clearly shows numerous circular indentations covering the lamina, c . 0´5 mm in diameter and at a density of c . 3 per mm sacs.

2 . These are interpreted as the position of attachment of resinous

Remarks.

This fossil has never been previously described or ®gured. Its interpretation as a male bennettite cone is to an extent speculative. However,the presence of numerous indentations,similar to those found in

Weltrichia ,is strongly suggestive. It is quite different from the ¯owers found in the Yorkshire Jurassic described by Harris (1969 a ) in having cuneate rays with a dentate distal margin.

CYCADOPHYTES incertae sedis

Genus TAENIOPTERIS Brongniart,1828a emend. nov.

Type species .

Taeniopteris vittata Brongniart,designated by Miller (1889).

Emended diagnosis . Leaves with a simple,entire-margined lamina. Midvein rigid,extending for entire length of leaf. Lateral veins approximately perpendicular to midvein,simple or forking at base. Evidence of epidermal structure not known.

Remarks.

The typi®cation of this morphogenus has been the subject of some confusion. In fact,it was resolved by Miller (1889) but this has been widely ignored. In view of its importance for understanding the taxonomic status of this morphogenus,we feel it worthwhile to go over again the historical background to the problem.

Brongniart (1828 a ) originally assigned three species to the genus ( T. vittata , T. latifolia and

T. bertrandii ) but none was at that time validly published. In principle,the lectotype of Taeniopteris could be chosen from any specimen that could be shown to have been available to Brongniart (1828 a ), including those ®gured by Brongniart (1831). On this basis,there are seven candidate specimens.

1. The specimen ®gured by Sternberg (1823,pl. 37,®g. 2) as èin BlattstuÈck einer Scitaminae' and which

Brongniart (1828 a ) included within T. vittata .

2. The four specimens ®gured by Brongniart (1831,pl. 82,®gs 1±4) with the protologue of T. vittata ,three of which originated from the Yorkshire Jurassic,the fourth from Scania. Harris (1969 a ) regarded these as belonging to the bennettite genus Nilssoniopteris .

3. The holotype of T. bertrandii ,from the Vicentian Alps,®gured by Brongniart (1831,pl. 82,®g. 5). This is clearly a fern and was transferred to Angiopteridium by Schimper (1869,p. 606).

4. The holotype of T. latifolia ,again from Stones®eld,®gured by Brongniart (1831,pl. 82,®g. 6). This con¯icts with the original diagnosis as the leaf is clearly not entire and the venation is anastomosed.

The last two of these candidates clearly must be rejected. As pointed out by Miller (1889),this leaves the

®ve T. vittata syntypes and we will later argue that,of these,the Sternberg (1823) specimen is the only sensible choice as lectotype.


The lectotype of T. vittata originated from Stones®eld and lacks cuticles. It is, therefore, impossible to be sure whether it is a cycad (similar to Nilssonia ) or a bennettite (similar to Nilssoniopteris ). We therefore concur with the often expressed view (e.g. Florin 1933) that Taeniopteris should be used as a morphogenus for entire-leafed cycadophyte foliage that cannot be assigned to either the cycads or bennettitaleans due to lack of cuticle evidence.

Nilssonia can sometimes be distinguished from

Nilssoniopteris on purely morphological characters. The midvein in Nilssonia can often not be seen on the upper surface of the leaf, being covered by the lamina; in Nilssoniopteris , the midvein is visible on both surfaces. Also, the veins in Nilssonia tend to be unforked, whereas those of Nilssoniopteris are often (but not always) forked. However, these morphological characters are not always reliable guides to distinguishing these morphogenera. The Stones®eld specimens are a case in point, as they show simple veins (suggesting Nilssonia ) but clearly show the rachis on what appears to be the upper surface of the leaf (suggesting Nilssoniopteris ). We, therefore, suggest that it is taxonomically useful to have a morphogenus for such leaves lacking cuticles. To clarify this, we have emended Brongniart's original diagnosis.

Florin (1933) and Harris (1969 a ) stated that T. vittata is the type species for the bennettite leaf morphogenus Nilssoniopteris Nathorst, 1909. This was because the specimens described by Nathorst

(1909) are conspeci®c with bennettite leaves from the Yorkshire Jurassic ®gured by Brongniart (1831) as

T. vittata (Thomas and Bancroft 1913). However, Nathorst (1909) only included one species in the protologue of Nilssoniopteris ( N. tenuinervis Nathorst), which must therefore be regarded as the type.

Harris (1964) later reinterpreted Nilssoniopteris tenuinervis as a cycad and transferred it to Nilssonia , but this is in total con¯ict with the species diagnosis and must be rejected.

N. tenuinervis is almost certainly a later taxonomic synonym of Nilssoniopteris solitarium (Phillips) comb. nov. (see later in this paper).

Nevertheless, the type of Nilssoniopteris remains N. tenuinervis and certainly cannot be Taeniopteris vittata .

Taeniozamites Harris, 1932 was erected for `species of the form-genus Taeniopteris which possess a bennettitalean cuticle' (p. 33). However, the only species that he unequivocally included in the morphogenus was T. vittata and so this must be regarded as the type. Consequently, Harris's generic name must be rejected as a later nomenclatural synonym of Taeniopteris . Gomolitzky (1987) argued that

Taeniozamites is synonymous with Nilssoniopteris . However, if the type of Nilssoniopteris is a bennettite leaf with preserved cuticles (see above), it must be quite different from the type of Taeniopteris (and consequently of Taeniozamites ).

Taeniopteris vittata Brongniart, 1831


T } 1823 ` Scitaminearum folium ' Sternberg, p. 37, pl. 37, ®g. 2.

1828 a Tñniopteris vittata Brongniart, p. 62 (name only).

* } 1831 Tñniopteris vittata Brongniart, p. 263 ( non pl. 82, ®gs 1±4 Nilssoniopteris sp.).

T } 1837 Tñniopteris vitata Brongniart; Lindley and Hutton, pl. 176, ®g.

B .

} 1838 Tñniopteris scitaminea Presl, in Sternberg, p. 139.

T } 1871 Tñniopteris scitamineñ-folia Phillips, p. 168, diagram 30, ®g. 8.

} 1904 Tñniopteris vittata Brongniart; Seward, p. 91.

Lectotype . We here designate as lectotype OUM J.23456 (Pl. 7, ®g. 1), which was ®rst ®gured by Sternberg (1823) and originated from Stones®eld.

Material.

In addition to the lectotype, there is a second OUM specimen: J.29620.

Description.

The two available specimens show the distal and proximal parts of what appear to be undivided leaves.

The total lengths of the leaves are unknown. The distal fragment is 47 mm long and has a maximum (basal) width of

27 mm (Pl. 7, ®g. 1); it is linguaeform, with gradually tapering margins and a bluntly rounded apex. The proximal

764 P A L A E O N T O L O G Y , V O L U M E 4 6 fragment is 50 mm long and 14 mm wide (Pl. 7, ®g. 2). At the base, there is what appears to be a short petiole, 5 mm long. From this petiole, the leaf width expands at ®rst rapidly and then more gradually along its length. Both fragments show a 1-mm-thick, deeply indented midvein along the entire length of the leaf. Numerous, ®ne lateral veins are emitted at 80±90 8 from the midvein, and extend in a more or less straight line to the leaf margin. As far as can be made out the veins are simple and there are about 30 veins per cm along the leaf margin.

Remarks.

Considerable confusion has surrounded the use of this species name, largely because of the failure to clearly designate a lectotype. Among the candidate syntypes, there are two groups of specimens:

(1) the Yorkshire Jurassic specimens and (2) the Stones®eld specimen. Whichever group the lectotype is selected from will result in some nomenclatural disruption but we believe that our choice is the lesser of two evils.

The Yorkshire specimens clearly belong to the species that Harris (1969 a ) and others have referred to as

Nilssoniopteris vittata (Brongniart) Florin, and which is a bennettite leaf. However, using this combination ignores the fact that there is a perfectly legitimate name that had been published for this bennettite species and which pre-dates Brongniart (1831), namely Scolopendrium solitarium Phillips, 1829. Although Harris

(1969 a ) acknowledged this fact, he illegitimately chose to suppress Phillips' species name in favour of

N. vittata . Designating one of the Yorkshire specimens as the lectotype of this species would also require the suppression of Nilssoniopteris Nathorst, 1909 in favour of Taeniopteris , as both would have the same type. Unless a formal proposal was made to conserve the former, it would require numerous new combinations to be proposed, as ` Nilssoniopteris ' species were transferred to Taeniopteris . It would also disrupt the normal use of Taeniopteris for entire cycad- or bennettite-like leaves, for which no cuticles or reproductive structures are known.

The consequences of designating the Stones®eld specimen as the lectotype of T. vittata are much less dramatic. The ` Nilssoniopteris vittata ' from Yorkshire would need to be renamed, but there is already an available species epithet (although it would require a new combination). However, it would have no impact on the normally accepted usage of Nilssoniopteris or Taeniopteris . This seems by far the most acceptable solution and hence our proposal to designate the Stones®eld specimen as the lectotype.

Consequently, we propose the following new combination:

Nilssoniopteris solitarium (Phillips) comb. nov. Basionym: Scolopendrium solitarium Phillips, 1829, p. 147, pl. 8, ®g. 5. Diagnosis: see Harris (1969 a , p. 69). Later synonym: Nilssoniopteris vittata Florin,

1933, non Brongniart, 1831.

KvacÏek and StrakovaÂ (1997) argued that Phyllites scitamineaeformis Sternberg, 1823 should take priority over T. vittata . It is far from clear, however, if Sternberg intended this as a formal taxonomic name.

More signi®cantly, no meaningful diagnosis was provided; the only description was ` . . . ein BlattstuÈck einer Scitaminea als ein Farrenkraut zu sehn' [ . . . a leaf-fragment of a Scitamineae resembling a fern]

(p. 37). The name cannot, therefore, be regarded as validly published and so cannot take priority over the validly published T. vittata .

Genus CONITES Sternberg, 1823 nov. emend .

1823 Conites Sternberg, p. 36.

1825 Bucklandia Sternberg, p. 4.

1828 a Bucklandia Brongniart, p. 128.


Figs 1±2.

Taeniopteris vittata Brongniart. 1, J.23456, lectotype, distal fragment of leaf; ´ 2. 2, J.29620, proximal fragment of leaf, showing short pedicel; ´ 3.

Fig. 3.

Carpolithes sp., V.2513a; ´ 4´5.


CLEAL and REES, Carpolithes , Taeniopteris

P L A T E 7


1828 a Clathraria Brongniart, p. 128 ( non Clathraria Brongniart, 1822).

1870 Yatesia Carruthers, p. 687.

1870 Fittonia Carruthers, p. 690.

Type species .

Conites bucklandii Sternberg (see below).

Emended diagnosis . Casts or compressions ofcycadophyte stems in which a thick stele is surrounded by a dense armour ofpetiole bases.

Remarks . The type ofthis genus, which originated from Stones®eld, was interpreted by Sternberg (1823) as a conifer cone. Buckland (1829) later suggested that it was a cone from the group of plants now known as the Bennettitales. However, the specimen is clearly a cycadophyte stem similar to those traditionally known as Bucklandia Sternberg, 1825. Sternberg had based Bucklandia on some stems from the Lower

Cretaceous ofsouthern Britain originally described as Clatharia anomala Stokes and Webb, 1824 (one has been re-®gured by Watson and Sincock 1992, pl. 18, ®g. 4). Brongniart (1828 a ) later renamed the

Stones®eld specimen as Bucklandia squamosa Brongniart, although he illegitimately retained the Stokes and Webb specimen (i.e. the type of Bucklandia ) in Clathraria . This confusion introduced by Brongniart is academic, however, as Bucklandia Sternberg, 1825 must be suppressed as a later taxonomic synonym of

Conites Sternberg, 1823.

Clathraria as interpreted by Stokes and Webb (1824) and Brongniart (1828 a ) is clearly also a taxonomic synonym of Conites . However, the type species of Clathraria is C. brardii Brongniart, 1822, which is based on a fragment of stem from a Late Carboniferous arborescent lycophyte, today more normally included in Sigillaria Brongniart, 1822. There is, therefore, no question of Conites being suppressed in favour of Clathraria .

Carruthers (1870) recognized two further morphogenera for cycadophyte stems preserved as casts,

Yatesia and Fittonia . However, ifthe above emendation ofits diagnosis is accepted, then both of

Carruthers' genera ®t within the circumscription of Conites (see also Watson and Sincock 1992).

Sternberg (1825) described four other species of Conites , which include Carboniferous sphenophyte foliage ( Conites armatus ), Carboniferous lycophyte cones ( Conites cernus ), Cretaceous conifer foliage

( Conites familiaris ) and Palaeogene conifer foliage ( Conites ornatus ). These clearly have little to do with

Conites in the sense used here, and should be excluded from the morphogenus.

Conites has not been widely used in the literature and, where it has, it has usually been for poorly preserved casts and adpressions ofconifer or cycad cones. As the type is unambiguously a cycadophyte stem, using Conites for such cones is obviously illegitimate. The only way that Conites could continue to be used for cones would be to conserve it formally with, perhaps, C. familiaris Sternberg or C. ornatus

Sternberg as the type. However, it is dif®cult to see how this would help signi®cantly to stabilize nomenclature as Conites has been so infrequently used for such cones. The preferable option must therefore be to emend the diagnosis of Conites to make its circumscription identical to that of Bucklandia

Sternberg. It also necessitates the establishment ofa number ofnew combinations, for those species traditionally included in Bucklandia . After consulting the Fossilium Catalogus , it is evident that some species that have been included in Bucklandia are anatomically preserved and have been correctly transferred to other genera, such as Cycadeoidea . However, the following taxa appear to be based on casts or adpressions, and thus fall within the circumscription of Conites .

Conites anomala (Stokes and Webb) comb. nov. Basionym: Clathara anomala Stokes and Webb, 1824, p. 42, pl. 45; pl. 46, ®g. 8; pl. 47, ®g. 4

A±D

.

Conites gigas (Seward) comb. nov. Basionym: Williamsonia ( Bucklandia ) gigas Seward, 1917, p. 425, ®g.

541.

Conites indica (Seward) comb. nov. Basionym: Bucklandia indica Seward, 1917, p. 488, ®g. 579.

Conites milleriana (Carruthers) comb. nov. Basionym: Bucklandia milleriana Carruthers, 1870, p. 687, pl. 55, ®g. 1.

Conites pustulosa (Harris) comb. nov. Basionym: Bucklandia pustulosa Harris, 1969 a , p. 173, pl. 6, ®gs 2,

4, 8.


TEXT-FIG.

B

3.

A

, Conites bucklandii Sternberg. J.29202, (?)bennettite stem with thick, ¯eshy petiole bases; ´ 0´85.

, J.43278; (?)seedling of the Pelourdea -bearing plant; ´ 1. Both specimens from the Stones®eld Slate, Stones®eld,

Oxfordshire.


Conites yatesii (Carruthers) comb. nov. Basionym: Cycadeoidea yatesii Carruthers, 1867 b , p. 199, pl. 9,

®gs 1±2.

Conites bucklandii Sternberg, 1823, nov. emend.

Text-®gure 3 A

* } 1823 Conites Bucklandi Sternberg, p. 36, pl. 30.

} 1828 a Bucklandia squamosa Brongniart, p. 128.

} 1829 Àmentum of a Cycadeoidea ' Buckland, p. 400.

} 1849 Cycadeoidea squamosa (Brongniart) Brongniart, p. 106.

} 1871 Bucklandia squamosa Brongniart; Phillips, p. 169, diagram 29.

} 1904 Cycadeoidea squamosa (Brongniart) Brongniart; Seward, p. 109.

Holotype . OUM J.29202.

Emended diagnosis . Stem up to 80 mm wide. Pith cast 21±23 mm wide, with irregular diamond-shaped marks. Helically arranged, thick petiole bases, 18 mm wide.

Material . In addition to the holotype, there is a second specimen, which may belong to this species: NHM V.4669.

Remarks . This species has usually been referred to as Bucklandia squamosa but, as pointed out above, this is a later nomenclatural synonym of Conites bucklandii and must be suppressed. Seward (1904) suggested that it should be referred to the genus Cycadeoidea , but this is normally used for petri®ed bennettite trunks.

There would be little to gain by widening the circumscription of this anatomically de®ned genus to allow the inclusion of casts and compressions, some of which cannot de®nitely be proved bennettitalean.

Seward (1904) placed a second Stones®eld specimen in this species (Natural History Museum specimen

V.4669). This is an approximately cylindrical structure with similar marks to those on the pith cast of the holotype. However, there are no leaf bases still attached and so its assignment to this species must be regarded as equivocal.

Class

PINOPSIDA

Order GINKGOALES

Family

GINKGOACEAE

Engler, 1897

Genus

GINKGO

Linnaeus, 1771

Type species. Ginkgo biloba L. (extant).

Ginkgo aff.

longifolius (Phillips) Harris, in Harris et al . 1974


?1845

Stricklandia acuminata Buckman, in Murchison, pl. 2, ®g. 2 ( nomen dubium ).

} 1871 Stricklandia acuminata Buckman; Phillips, p. 169.

} 1904 Baiera Phillipsi Nathorst; Seward, p. 101, text-®g. 10; ?pl. 9, ®g. 2.


Figs 1±2.

Ginkgo aff.

longifolius (Phillips) Harris, V. 3422 (part and counterpart); ´ 2´25.

Figs 3±5.

Brachyphyllum expansum (Sternberg) Seward. 3, V.27703, leafy shoot showing three orders of branching;

´ 1. 4, BMNH 38932, leafy shoot that yielded details of epidermal structure ®gured by Hill (1986); ´ 2. 5, 41382a, leafy shoot with cone attached; ´ 2.


CLEAL and REES, Brachyphyllum , Ginkgo

P L A T E 8


Material.

The only specimen is NHM V.3422 (part and counterpart). The part was ®gured by Seward (1904, text-®g. 10).

Description.

The only specimen of this type from Stones®eld consists of part of a leaf with four segments, separated by deep incisions, the middle incision being deeper than the other two. The longest segment is 42 mm long and 5 mm in maximum width. The segments are parallel-sided for most of their length, converging slightly in their distal part. The apex of each segment is broken and its form is thus unknown. Venation is not well preserved, but seems to consist of parallel veins without a distinct midvein.

Remarks.

Seward (1904) ®rst ®gured the only ginkgophyte leaf known from Stones®eld. However, this illustration is misleading because it suggests that the leaf segments have converging margins and an acute apex. Seward (1904, pl. 9, ®g. 2) ®gured a second specimen of a similar leaf fragment, but this came from Gloucestershire (it was probably the same specimen ®gured earlier by Buckman in

Murchison 1845).

The morphology of the Stones®eld specimen compares well with Ginkgo longifolius as illustrated by

Harris et al . (1974) from Yorkshire. As pointed out by Czier (1998), however, the infraspeci®c morphological variability of Ginkgo leaves makes it impossible to identify them accurately without epidermal evidence; specimens lacking such evidence should at best be assigned to a species only with an

àff.'.

Order

PINALES

Family UNKNOWN

Genus

BRACHYPHYLLUM

Brongniart, 1828 a emend. Harris, 1979

Type species .

Brachyphyllum mamillare Brongniart ex Lindley and Hutton, 1835.

Remarks.

We have followed Harris (1979) and used this as a generalised morphogenus for conifer foliage with short, broadly attached leaves.

Brachyphyllum expansum (Sternberg) Seward, 1919 emend. Kendall, 1949

Text-®gure 4; Plate 8, ®gures 3±5; Plate 9; Plate 11, ®gure 1

* } 1823 Thuites expansus Sternberg, p. 38, pl. 38, ®gs 1±2.

} 1823 Thuites articulatus Sternberg, p. 36, pl. 33, ®g. 3.

} 1823 Thuites cupressiformis Sternberg, p. 36, pl. 33, ®g. 2.

} 1823 Thuites divaricatus Sternberg, p. 38, pl. 37, ®gs 1, 4; pl. 39.

} 1825 Thuites expansus Sternberg, p. XXXVIII.

} 1825 Thuites articulatus Sternberg, p. XXXVIII.

} 1825 Thuites cupressiformis Sternberg, p. XXXVIII.

} 1825 Thuites divaricatus Sternberg, p. XXXVIII.

} 1833 Caulerpites expansus (Sternberg) Sternberg, p. 22.

} 1871 Thuytes expansus ? Sternberg; Phillips, p. 171, diagram 31, ®gs 4±5.

} 1871 Thuytes articulatus Sternberg; Phillips, p. 171, diagram 31, ®gs 1±3.

} 1871 Thuytes cupressiformis Sternberg; Phillips, p. 171.

} 1871 Thuytes divaricatus Sternberg; Phillips, p. 171, diagram 31, ®gs 7±8.

} 1904 Thuites expansus Sternberg; Seward, p. 142, text-®g. 19; pl. ®gs 1, 4.

} 1919 Brachyphyllum expansum (Sternberg) Seward, p. 317, ®g. 754.

1948 Brachyphyllum stemonium Kendall, p. 244, ®gs 7±8 (according to Kendall 1949).

} 1949 Brachyphyllum expansum (Sternberg) Seward; Kendall, p. 308, text-®gs 1±2.

} 1986 Pagiophyllum araucarinum (Pomel) de Saporta; Hill, ®g. 9.3.

} 1998 Brachyphyllum expansum Kendall [ sic ]; Cleal and Rees, pl. 7.

Holotype . OUM J.1114, from the tilestones of Stones®eld (`Stones®eld Slate').


Material.

In addition to the holotype, there are 22 other OUM specimens: J.1112 (syntype of Thuytes divaricatus ; location of other two syntypes unknown), J.1115 (holotype of Thuytes articulatus ), J. 1131, J.1135 (holotype of

Thuytes cupressiformis ), J.21660, J.43287±J.43288, J.43293±J.43298, J.43300±J.43301, J.43308±J.43309,

J43313±J.43315, J.43317, and an unnumbered specimen. There are also 47 NHM specimens: 38931±38932,

41169±41170, 41372, 41382, 41382a, 41384 (2 specimens), 52817, 52937a, V.81 (10 specimens), V.81a, V.1019

(3 specimens), V.2514±V.2515 (2 specimens), V.2515a, V.3417, V.3637, V.4072±V.4073, V.4392, V.4678, V.4688,

V.4692, V.6577±V.6578, V.7612, V.9381, V.9710±V.9711, V.9717, V.11519, V.27703 and V.31151.

Description.

Numerous conifer fragments showing mainly alternate lateral or occasionally dichotomous branching, usually in one plane. There are up to three orders of branching (Pl. 8, ®g. 3; Pl. 11, ®g. 1). The widest preserved axis is

4 mm wide, the ultimate branches about 2 mm wide.

The leaves are helically arranged; where observable, they seem to be in a 2/5 phyllotaxy. They are usually closely adpressed to the stem (Pl. 9, ®gs 2±3)but are sometimes protruding, especially in the wider stems (Pl. 8, ®g. 4; Pl. 9,

®g. 1). The leaves have a broad basal cushion and taper distally to an obtuse apex. The free part of the leaf always projects above its own cushion. On the largest stems, the leaves are up to 6 mm long (4´5 mm free part)and 4 mm wide; on the smallest, ultimate branches, they are about 2 mm long ( c.

1 mm free part)and 2 mm wide.

The leaves are thickly cutinized. Stomata are arranged in irregular rows on both upper and lower sides of leaf

(Text-®g. 4 B±C ). Each stomatal apparatus consists of 4±7 subsidiary cells (Text-®g. 4 E ), each with a prominent papilla that over-arches the stomatal pore (Text-®g. 4 F ). No guard cells were seen, making it impossible to determine the orientation of the stomata. The entire stomatal apparatus is somewhat sunken and is c.

70 m m in diameter in surface view. Stomata density crenulate (Text-®g. 4

D

).

c.

95 per mm 2 . Other epidermal cells are subrectangular, 15±40 m m in size, with prominently cutinized anticlinal walls (Text-®g. 4

A

). The cuticle from the margin of the leaf appears to be ®nely

Remarks.

Under normal circumstances, the interpretation of such conifer foliage based on impression material is nigh on impossible. However, in Stones®eld we have been fortunate, as there is good evidence of epidermal structure and attached cones. Kendall (1949)reported some surprisingly large pieces of cuticle preserved in these fossils, but unfortunately did not illustrate them. We provide, for the ®rst time, a photographic record of these cuticles (Text-®g. 4). This is supplemented by evidence from an apparently poorly preserved specimen (BMNH 38932)found during the early phases of the present study. C. R. Hill

(formerly of The Natural History Museum, London)prepared a latex replica from this specimen, which under the SEM showed clear details of the stomata. In particular, it demonstrated that (1)the stomata occur on both surfaces of the leaf, (2)they are strongly papillate, (3)they are sunken, and (4)they occur in more or less distinct rows but not in sunken furrows.

The evidence of attached reproductive structures is based on a specimen ®gured as a drawing by Kendall

(1949, ®g. 1

D

)and a specimen in Oxford Museum (Pl. 8, ®g. 5). The leafy shoots have not yielded cuticles but are morphologically indistinguishable from those that have. The terminally attached cones are poorly preserved but appear very similar to the better-preserved Stones®eld cones referred to here as

Classostrobus sp. This would suggest that they belong to the Cheirolepidiaceae (see discussion later).

The problem arises, however, that other reproductive structures have been found at Stones®eld, which suggest the existence of the Araucariaceae here. Either the foliage of this araucariacean has been selectively discriminated against during transportation prior to fossilization or there are two natural species of conifer represented within the foliage that we have referred to as B. expansum . At this stage we cannot decide which is the case and so must continue to regard this foliage species as a generalized morphogenus for foliage within the order Pinales.

This is the commonest species found at Stones®eld. Leaf shape varies considerably, which caused

Sternberg to establish several different species. As pointed out by Seward (1904)and Kendall (1949),


Figs 1±4.

Brachyphyllum expansum (Sternberg)Seward. Stones®eld Slate, Stones®eld, Oxfordshire. 1, V.6577, shoot with more robust leaves; ´ 2. 2, V.2514; ´ 1´5. 3, BMNH 52817; ´ 1´5. 4, V.81a, shoot bearing very slender ultimate branches; ´ 1´5.

CLEAL and REES, Brachyphyllum

P L A T E 9


TEXT-FIG.

A

4.

Brachyphyllum expansum (Sternberg) Seward, Stones®eld Slate, Stones®eld, Oxfordshire; cuticles.

, V.2514d, side view of almost complete leaf; ´ 50.

B , V.2935b, cuticle from upper part of leaf showing irregular rows of stomata; note the sinuous row of holes on the right of the cuticle, where the stomatal apparatuses have been lost; ´ 50.

C , V.4678a, cuticle from lower part of leaf; ´ 50.

D , V.6587a, cuticle from margin of leaf showing ®ne crenulation; ´ 100.

E , V.2514d, stomata surrounded by clear ring of subsidiary cells; ´ 100.

F , V.2514b, stomata with papillae; ´ 100.

however, there is a complete gradation between the different morphologies, making it impossible to justify the taxonomic separation.

Very similar is Brachyphyllum crucis Kendall from the Oxford Clay of Wiltshire, the Forest Marble of

Oxfordshire and the Yorkshire Jurassic (Kendall 1947, 1952; Harris 1979), which has similar-shaped, helically arranged leaves with a frilled margin. It is also known to have borne a cheirolepidiacean male

774 P A L A E O N T O L O G Y , V O L U M E 4 6 cone (van Konijnenburg-van Cittert 1971, 1972). However, B. crucis can be distinguished by the stomata, which are not arranged in distinct rows and have no or only weakly developed papillae. Harris (1979) also noted that B. crucis does not seem to have abscised the `richly and regularly' branched shoot systems as did B. expansum . Nevertheless, it seems likely that the two species are closely related and it may be signi®cant that both tended to favour (although not exclusively) marine-in¯uenced habitats.

The common Brachyphyllum from the Yorkshire Jurassic ( B. mamillare Lindley and Hutton), which seems to have preferred deltaic conditions, has much shorter leaves than B. expansum . Also, the stomata are not surrounded by prominent papillae and are often in sunken furrows (Harris 1979). According to

Harris, it is probably an araucariacean conifer.

In his discussion on the similar B. crucis , Harris (1979) compared it with a number of other Jurassic conifer remains, but all differ from B. expansum . They lack either papillate stomata, adaxial stomata, stomata in clear rows, or frilled leaf margins. Barnard (1968) identi®ed specimens from the Elburz

Mountains of Iran as B. expansum . However, Barnard and Miller (1976) recognized that they differed from true B. expansum in having whorled leaves and therefore placed them in a new species, Cupressinocladus pseudoexpansum .

Genus ELATOCLADUS Halle, 1913 emend. Harris, 1979

Type species .

Elatocladus heterophylla Halle, 1913.

Remarks.

There have been various views as to the circumscription of this morphogenus. Halle (1913) essentially used it as a catch-all for any conifer shoot that could not be placed in one of the better-de®ned genera. Seward (1919) gave it a slightly tighter morphological de®nition, using it for conifer shoots with spreading needles. Florin (1958) attempted to rede®ne it as a `natural' genus by incorporating cuticular details in the diagnosis, thereby excluding many species. For one of these, he created the new combination

Sewardiodendron laxum (Phillips) Florin, since he found it had taxodiaceous-like cuticles. However,

Harris (1969 b ) argued against narrowing the circumscription in this way for such sterile conifer shoot fragments and he reverted to a wider, morphological de®nition. The de®nition currently used by most palaeobotanists is that eventually given by Harris (1979, p. 104): `Fossil conifer shoot bearing elongated, dorsiventrally ¯attened leaves with a single vein. Leaves divergent from the stem.'

Elatocladus cf.

laxus (Phillips) Harris, 1979

Plate 10

1828 a Taxites podocarpoides Brongniart, p. 108 (name only).

} 1958 Sewardiodendron laxus (Phillips) Seward ( non Phillips); Florin, p. 332, pl. 45, ®gs 1±4 [?

non p. 303, pls 25±27 Elatocladus laxus (Phillips) Harris, 1979].

Material . Three OUM specimens: J.9545±J.9547. There is also a specimen in the Museum d'Histoire Naturelle, Paris, which Brongniart had labelled as Taxites podocarpoides (this is the counterpart of OUM J.9546).

Description.

Leafy shoot, with elongate leaves spaced widely along a slender axis (Pl. 10, ®g. 2), except near the shoot apex where they are more clustered (Pl. 10, ®g. 1). The leaves are at 50±80 8 to the axis, and apparently arranged in a single plane. They are 5±30 mm long and 0´5±2´0 mm wide, with a bluntly acuminate apex and a constricted base

(Pl. 10, ®g. 3).


Figs 1±3.

Elatocladus cf.

laxus (Phillips) Harris. 1, J.9546, terminal part of shoot with one side branch and small leaves; ´ 3. 2±3, J.9545. 2, more proximal part of a shoot showing larger leaves; ´ 2. 3, close-up of a leaf showing constricted base; ´ 8.


CLEAL and REES, Elatocladus

P L A T E 1 0


Remarks.

The known fossils of this species were fully documented by Florin (1958). He assigned them to

Sewardiodendron (i.e.

Elatocladus ) laxus . As pointed out by Harris (1979), however, this species normally has broadly attached leaves, whereas the Stones®eld shoots have basally constricted leaves. Also, E. laxus has helically arranged leaves, although again as pointed out by Harris (1979), poor preservation of this thin-leafed conifer can sometimes make them look as if they are in a single plane. In other characters, the

Stones®eld shoots do seem similar to E. laxus . A lso, E. laxus is thought to be taxodiaceous, and possible taxodiaceous male cones have been found at Stones®eld (see next species). In the absence of a better attribution, we have placed this material in E.

cf.

laxus .

Florin (1958) ®gured the specimen on which Brongniart (1828 a ) had based his Taxites podocarpoides and showed that it is clearly the same as this conifer. However, as Brongniart provided neither diagnosis nor illustration, nor referred to a previously published diagnosis, the name is invalidly published. Phillips

(1871) used this name for some Stones®eld fossils with robust foliar segments, which are assigned here to

Pachypteris macrophylla (Brongniart) comb. nov. Based on Phillips' error, Seward (1904) placed

T. podocarpoides in the synonymy of Thinnfeldia (i.e.

Komlopteris ) speciosa .

Genus MASCULOSTROBUS Seward, 1911

Type species .

Masculostrobus zeilleri Seward, 1911.

Remarks . This morphogenus is now used for coniferous male cones of uncertain family position

(Grauvogel-Stamm and Schaarschmidt 1979).

Masculostrobus sp.


} 1871 `Fruits of Thuytes' Phillips, p. 171, diagram 32, ®gs 5, 8±9.

} 1904 Thuites expansus Sternberg (male ¯owers); Seward, p. 147.

} 1949 Male cones; Kendall, p. 318.

} 1968 Cones associated with Brachyphyllum expansum (Sternberg) Seward; Barnard, p. 171, Text-®g. 2 E±G .

Material.

Four OUM specimens: J.21650a/b (part and counterpart), J.21651, J.21652, and J.21657. Two NHM specimens: 52937 and V.12299.

Description.

The cones are 4 mm wide, the longest preserved length being 11 mm (Barnard 1968, text-®g. 2 F ), but still incomplete. Three (Pl. 11, ®gs 2±3; also Barnard 1968, text-®g. 2

E±F

) show a longitudinal section through a parallelsided cone, with a 0´5-mm-wide cone axis. Stiff peltate sporophylls are attached at about right-angles to the cone axis, and are c.

2 mm long. In longitudinal section, the sporophylls are spaced at c.

1 mm. The fourth specimen (Barnard

1968, text-®g. 2

G

) represents an internal cast of the lower part of a cone and shows its surface features. This shows the peltate heads of the bracts to be rhomboidal, 3 mm wide and 2 mm high. It also shows that the sporophylls are helically arranged with (according to Barnard 1968) 2 3 parastichies.

EXPLANATION OF PLATE

11

Fig. 1.

Brachyphyllum expansum (Sternberg) Seward, BMNH 38931, leafy shoot showing three orders of branching with tightly adpressed leaves; ´ 1.

Figs 2±3.

Masculostrobus sp., ´ 2. 2, BMNH 52937. 3, V.12299.

Figs 4±6.

Classostrobus sp. 4, V.12293, longitudinal section through cone, viewed after coating with ammonium chloride; ´ 2. 5, V.12302, similar section but viewed on polished surface of rock; ´ 2. 6, V.4696, outer surface of cone; ´ 2.

Fig. 7. (?)Araucariacean male cone, V.3441; ´ 2.



P L A T E 1 1


Remarks.

Seward (1904) interpreted these as the male cones of the plant that bore the Brachyphyllum expansum foliage and the larger cone that he interpreted as female (called here Classostrobus sp.).

However, these larger cones are now recognised as being also male and so obviously cannot have belonged to the same plant as B. expansum / Masculostrobus sp. It is also unlikely that it is the male counterpart of the

Araucarites ovules found here, as a rather different pollen cone is interpreted as ful®lling that role

(V.3441, see below). Among the Yorkshire Jurassic conifers, the nearest comparison seems to be with the male cones of the taxodiaceous Elatides thomasii Harris, 1979, although no foliage of the type associated with this species is known from Stones®eld.

Family CHEIROLEPIDIACEAE Takhtajan, 1963

Genus CLASSOSTROBUS Alvin et al.

, 1978

Type species .

Classostrobus risha (Barnard) Alvin et al ., 1978.

Remarks . This morphogenus was erected for male cones of the Cheirolepidiaceae. No pollen occurs in the

Stones®eld cones to verify that they are cheirolepidiacean. However, they are very similar morphologically to the type species of Classostrobus , which contains Classopollis pollen (Barnard 1968). We are, therefore, reasonably con®dent that the Stone®eld cones belong to the same morphogenus.

It is arguable that these cones should be merely referred to as `cones associated with Brachyphyllum expansum ' as did Barnard (1968). However, more than one natural species of conifer is probably included within the leafy shoots referred to B. expansum . We do not, therefore, know whether these cones belonged to the `real' B. expansum (i.e. the natural species that bore the holotype of B. expansum ) or to a species with morphologically similar shoots. We have, therefore, opted to assign the cones to a separate morphogenus.

Classostrobus sp.


1845 Murchison, p. 67, pl. 1, ®g. 6 A±B .

} 1871 `Fruits of Thuytes ' Phillips, p. 171, diagram 32, ®gs 6±7, 10±11.

} 1904 Thuites expansus Sternberg (female ¯owers); Seward, p. 147, pl. 9, ®g. 4.

} 1949 Brachyphyllum expansum (Sternberg) Seward (cone); Kendall, p. 314, ®gs 1 B±D , 2 A±C , E±F .

} 1968 Cones associated with Brachyphyllum expansum (Sternberg) Seward; Barnard, p. 171, text-®g. 2 D , I .

Material.

There are nine OUM specimens: J.1132±J.1134, J.21652±J.21654, J.21660 (attached to shoot), J.21661, and

J.21663. There are a further seven NHM specimens: 41382a (attached to shoot), 41404, V.3439, V.4696, V.6578,

V.6587 and V.12293.

Description.

Cones, mostly found isolated, but two known terminally attached to shoots of Brachyphyllum expansum

(see remarks on that species). The cones vary from 10±22 mm long and 5±16 mm wide. The larger cones are only a little longer than broad, and have a woody appearance (Pl. 11, ®gs 4±6); the smaller cones, which look more ¯eshy, tend to be up to twice as long as broad. Only the smaller cones are known attached to shoots and are interpreted as immature equivalents of the larger ones.

When seen in longitudinal section (Pl. 11, ®gs 4±5) the larger cones have a cone-axis 3 mm wide. These bear peltate scales borne on slender stalks, the latter being up to 5 mm long and 1 mm wide. The heads are 5±7 mm in size, have a rhomboidal face, and overlap with the heads of the more distal scales. Neither ovules nor pollen-sacs are preserved in the cavity between the head and the cone axis.

Remarks.

Seward (1904) and Kendall (1949) interpreted these as the female cones of the plant bearing

Brachyphyllum expansum foliage. Kendall noted that all the cones appeared empty and she thought that the ovules must already have been shed. However, it is dif®cult to see how the ovules could have escaped from the still tightly packed scales. By comparing them with similar but better-preserved cones from Iran,


Barnard (1968) suggested that they might instead be male cones, with pollen sacs rather than ovules having been borne on the scales. There is still no evidence of the pollen sacs, but their absence is easier to understand than a lackof ovules from a female cone.

Barnard (1968) recognized two types of such cone from Stones®eld: the smaller, more ¯eshy cones, including the two examples attached to leafy shoots (OUM J.21660 and NHM 41382a); and the larger, more woody-looking cones, only known detached. Although there are some differences in the shape of the cones, the overall arrangement and shape of the scales looks similar. In our view, they simply represent the juvenile and mature forms of the same type of cone.

Family ARAUCARIACEAE Henkel and Hochhstetter, 1865

Remarks.

Abundant arauraciacean cone scales and a possible male cone have been found at Stones®eld, but no unequivocal foliage. All of the foliage with either attached cones or else yielding anatomical data is cheirolepidiacean ( Brachyphyllum expansum ). However, it is likely that some of the Stones®eld conifer foliage assigned to B. expansum is in fact araucariacean, but we do not at present have a means of distinguishing it from the cheirolepidiacean shoots on gross morphology.

Genus

ARAUCARITES

Presl, in Sternberg 1838

Lectotype species .

Araucarites goeppertii Presl, in Sternberg 1838 (designated by BuzÏek et al.

1968, p. 555).

Remarks.

There are complications with the nomenclature of Araucarites . Zijlstra and van Konijnenburgvan Cittert (2000) have proposed that Araucarites Presl, in Sternberg 1838 should be conserved with

A. goeppertii as the lectotype species, for araucariaceous female cones and cone scales. However, Florin

( in Reid and Chandler 1925, p. 50) argued that the types of A. goeppertii were of very little value, as they lacked any distinguishing characters (see also BuzÏek et al.

1968). BuzÏek et al.

argued that it would be advisable to conserve the morphogenus with another better-de®ned type, probably from the Mesozoic, but this did not form part of the Zijlstra and van Konijnenburg-van Cittert (2000) proposal.

Isolated remains of wedge-shaped, woody bracts, with what seems to be a fused ovuliferous-scale, occur commonly in Jurassic ¯oras. Although not all specimens can be unequivocally assigned, some show ovuliferous-scales with a single ovule and a free distal ligule, which suggest that they belong to the

Araucariaceae. Some authors assign fossil bract/ovuliferous-scale units to the extant genus Araucaria but in our view it is better to assign such isolated organs to the fossil morphogenus Araucarites .

Araucarites brodiei Carruthers, 1869

Plate 12

?

} 1837 Carpolithes ; Lindley and Hutton, pl. 193, ®g. A3.

* } 1869 Araucarites Brodiei Carruthers, p. 3, pl. 2, ®gs 1±6.

} 1871 Araucarites Brodiñi Carruthers; Phillips, p. 171, diagram 32, ®g. 4.

?

} 1871 Carpolithus Lindleyanus Carruthers; Phillips, p. 171, diagram 32, ®g. 1.

} 1904 Araucarites Brodiei Carruthers; Seward, p. 136, pl. 3, ®g. 5; pl. 12, ®g. 2.

?

} 1904 Araucarites sp.; Seward, p. 139, pl. 12, ®g. 6.

Lectotype . The syntypes all originated from Stones®eld and are now in the NHM and OUM. The specimen re®gured by

Seward (1904, pl. 12, ®g. 2) is here designated the lectotype (NHM V.3364). Despite the comments of Carruthers

(1869) that the specimen was from Stones®eld, the label and register both con®rm that the specimen originated from

Sevenhampton.

Material.

There are ®ve NHM Stones®eld specimens: V.6593, V.9707, V.12300, 41384 and 41404. There are another

®ve OUM specimens, J.1130 (®gured by Phillips 1871), J.1131, J.43294, J.43298 and J.54967. The Manchester

Museum has a specimen, 197. The NHM also has 15 isolated ovules that are provisionally included in this species,

V.1018 (seven specimens), V.3443±V.3444, V.6346±V.6347, V.6591, V.10681, V.11141, and V.12295.


Description.

Cuneate bracts, up to 30 mm long and 18 mm wide, have a woody appearance. Some bracts show a marked 10 mm long distal beak, although this is often broken off. An oval depression normally occurs in the lower part of the bract, marking the position of the cone scale. When found detached, the cone scales are oval or slightly cuneate,

20±25 mm long and 10±12 mm wide, with a small ligule at the distal end.

Inverted, platyspermic ovules can occur either detached (Pl. 12, ®gs 4±5), attached to a cone scale (Pl. 12, ®g. 1), or attached to a bract (Seward 1904, pl. 3, ®g. 5). When attached to a bract, they occur in the proximal part of the bract.

They are up to 11±15 mm long and 6±7 mm wide, broadest near their chalazal end and tapering gradually to a slender micropylar end. Some ovules show a 0´5-mm ¯attened rim, probably the remains of the integument.

Remarks.

These fossils are clearly the remains of araucariacean bract-scale complexes. They are similar to

Araucarites phillipsii Carruthers from the Yorkshire Jurassic and Harris (1979) suggested that some of the

`Stones®eld specimens' (in fact, most originated from Sevenhampton) might belong to that species.

However, the A. phillipsii bracts are consistently smaller than those from Stones®eld, and the ovules are preserved embedded in the middle rather than the lower region of the bract.

Araucaria brownii Stockey, 1980, from the ?Oxfordian of Osmington Mills, southern England was described from a cone preserved in a limestone block. It has well-preserved ovuliferous scales and ovules, which are similar in size and shape to those from Stones®eld. However, the Osmington Mills specimen does not preserve the bracts, hindering any further comparison.

Barnard (1968) suggested that there might be two types of bract-scale complexes preserved at

Stones®eld: those with broad bracts and a relatively small apical beak, and those with narrower bracts and a prominent beak. However, the two types of bract seem to be associated together and those with an apparently small beak are probably just cases of it having been damaged during fossilization. We have little doubt that we are dealing here with just one species.

Seward (1904) separately described isolated araucariacean ovules from Stones®eld as Araucarites sp.

However, as they seem indistinguishable from those found with the A. brodiei bracts, we see little reason for treating them separately.

(?)Araucariacean male cone

Plate 11, ®gure 7

} 1904 Thuites expansus Sternberg (male ¯owers); Seward, p. 147.

} 1949 Male cones; Kendall, p. 318.

} 1968 Cones associated with Brachyphyllum expansum (Sternberg) Seward; Barnard, p. 171, text-®g. 2 H .

Material.

A single specimen: NHM V.3441.

Description.

The ovoid cone is preserved as a complete longitudinal section, and is 10 mm wide and 18 mm long. The cone axis is 2 mm wide and seems to show surface markings, possibly representing the attachment scars of the sporophylls. The sporophylls are up to 4 mm long and in their distal end bend upwards towards the cone apex; these imbricating distal ends of the sporophylls are c.

1 mm long. In longitudinal section the sporophylls are spaced at c.

0´5 mm. According to Barnard (1968), the parastichies are in an 8 13 arrangement.

Remarks.

This is among the specimens that were interpreted by Seward (1904) as male cones of

Brachyphyllum expansum . However, it is now known that Classostrobus is the male cone of


Figs 1±5.

Araucarites brodiei Carruthers, Stones®eld Slate, Stones®eld, Oxfordshire. 1, V.12300, detached cone scale with ovule still attached; ´ 5. 2, BMNH 41384; cuneate bract showing depression marking position of attachment of cone scale; also showing fragment of Brachyphyllum expansum shoot; ´ 2. 3, V.6593, similar bract showing longitudinal ribs; ´ 2. 4±5, isolated ovules; ´ 4. 4, V.10681. 5, V.6591.

CLEAL and REES, Araucarites

P L A T E 1 2


B. expansum and that it is cheirolepidiacean. Instead, it may have been the male cone of the plant that bore the Araucarites brodei ovules. This is based on its similarity to the male cone from the Yorkshire Jurassic described by Harris (1979)attached to Brachyphyllum mamillare Lindley and Hutton foliage, and which is associated with Araucarites phillipsii Carruthers cone scales and ovules. The cones are a similar size and shape, and the distal ends of the sporophylls are not peltate. Furthermore, the sporophylls seem in both cases to be arranged in 8 13 parastichies.

Division

UNKNOWN

Genus

PELOURDEA

Seward, 1917 emend. Ash, 1987

Type species . Seward unequivocally stated that Pelourdea is a replacement name for Yuccites , and so the type of the former must be the same as the latter (i.e.

Y. vogesiacus Schimper and Mougeot, 1844). The holotype of P. vogesiacus is reported lost (Arber 1907, p. 115)and a neotype will have to designated. However, this is beyond the scope of the present paper.

Diagnosis (as emended by Ash 1987). Plant short; stem erect, unbranched, narrow, bearing leaves in a helix. Leaves lanceolate to linear-lanceolate, margins entire, apex acute to acuminate, base narrowing slightly to clasp stem; veins radiating from base, generally parallel, ending in lateral margins and apex.

Remarks.

This genus corresponds to Yuccites Schimper and Mougeot, 1844, which was originally described for leaves from the Triassic of the Vosges, France. As pointed out by Seward (1917), however, this name was preoccupied when used by Schimper and Mougeot, and so he proposed the new name

Pelourdea .

Much of Seward's interpretation of Pelourdea was based on the specimens ®gured by Arber (1907)and

Wills (1910)as Z amites grandis Arber, which he regarded as synonymous with P. vogesiacus . Of the species mentioned in the protologue, only P. megaphylla (Phillips)Seward from Stones®eld was well circumscribed and based on several specimens demonstrating the range of morphological variation.

Pelourdea imhof®i (Halle)Seward and P. keuperiana (Compter)Seward are based on single isolated leaves.

Pelourdea hadroclada (Halle)Seward shows leaves helically attached to a branch, but the leaves are so poorly preserved that it is impossible to establish the morphological characteristics that would de®ne the species.

Pelourdea mirabilis (VelenovskyÂ)(basionym Krannera mirabilis Corda ex VelenovskyÂ, 1885) was based on a conifer stem with helically-arranged leaf-scars from the Cretaceous of Bohemia, which has been assigned by HlusÆtik (1976)to Dammarites albens Presl, in Sternberg 1838.

The genus has been most recently investigated by Ash (1987), who provided an emended diagnosis and a reconstruction. We accept his emendation of the diagnosis, but note that his reconstruction, especially that on his text-®gures 4b and 5, greatly exaggerates the degree to which the leaves expand basally to clasp the stem. Both his specimens (Ash 1987, pl. 1, ®g. 3

B

; pl. 2, ®gs 4±5), those ®gured by Wills (1910), and our material show a gradually tapered base that wraps slightly around the stem, but does not embrace it to the same extent as suggested by Ash. Ash used the clasping form of the leaf base as one of the crucial differences between Pelourdea and the Palaeozoic morphogenus Cordaites . However, Cordaites leaves do in fact clasp the stem slightly, as is clearly shown by the specimen ®gured by Grand'Eury (1877, pl. 19)


Fig. 1.

Pelourdea megaphylla (Phillips)Seward, J.1174, holotype; ´ 1.

Fig. 2.

Pachypteris macrophylla (Brongniart)comb. nov., J.43291, bipinnate segment with elongate pinnules; ´ 2.

Fig. 3.

Komlopteris speciosa (Ettingshausen)comb. nov., V.4074, terminal part of leaf with robust apical pinnule;

´ 1´25.



P L A T E 1 3


(and redrawn by Ash 1987, text-®g. 4

A

). All of the larger leaves assignable to Pelourdea show a similar mode of attachment to Cordaites .

Should such Mesozoic leaves therefore be assigned to Cordaites ? Seward (1917, p. 278) proposed the name Pelourdea ` . . . for leaves of the Yuccites type which in form, venation, and spiral phyllotaxis agree with those of Cordaites but cannot con®dently be assigned to that genus or even to the Cordaitales.' We totally concur with this view, especially as no cordaitalean fructi®cations have ever been found in the

Mesozoic.

Florin (1936) and Wesley (1958) assigned some very similar Mesozoicleaves to the morphogenus

Desmiophyllum Lesquereux, 1878. However, the type of Desmiophyllum is a leafy cordaite shoot from the

Pennsylvanian (Upper Carboniferous) of the Appalachians (Lesquereux 1880) and is almost certainly synonymous with Cordaite s. Using the same logicas in the previous paragraph, we do not feel it wise to use Desmiophyllum for Mesozoicleaves. Harris et al.

(1974) used the name Desmiophyllum for leaves from the Yorkshire Jurassic associated with the male cone Ixostrobus , but they are far more slender than typical Pelourdea leaves and probably have little to do with them.

There are a number of conifer morphogenera that bear some similarity especially to the smaller

Pelourdea leaves (e.g. Pl. 14, ®g. 3), most notably Podozamites Braun, 1843 and Lindleycladus Harris,

1979. According to Harris (1979), these morphogenera can only be recognized reliably by their epidermal features and this is unknown in Pelourdea . However, Podozamites and Lindleycladus can be distinguished from Pelourdea by the leaves being far more constricted at the base and there being only one vein entering each from the stem.

Florin (1936) mentioned Zeugophyllites Brongniart, 1828 a as another morphogenus of Mesozoic parallel-veined veins that is similar to what is called here Pelourdea . However, this is based on a type species ( Z. calamoides Brongniart) that is a nomen nudum and must, therefore, be rejected.

The af®nities of Pelourdea remain obscure in the absence of reproductive structures. SchluÈter and

Schmidt (1927) and Grauvogel-Stamm (1978) reported Pelourdea -like leaves from the Triassicof France associated with Willsiostrobus male cones, but they are not attached and a similar association has not been reported from other Pelourdea localities. The stomata reported in Triassic Pelourdea -like leaves are similar in arrangement and structure to those in Palaeozoic Cordaites leaves (Florin 1936), which suggests it is a gymnosperm. However, it is most unlikely to be closely allied to the Cordaitales as no reproductive structures similar to Cordaitanthus have ever been reported from the Mesozoic. We conclude that

Pelourdea is a gymnosperm, most probably related to the conifers, but beyond that it is impossible presently to say.

Pelourdea megaphylla (Phillips) Seward, 1917

Plate 2, ®gure 4; Plate 5, ®gure 3; Plate 6, ®gure 2; Plate 13, ®gure 1; Plate 14, ®gures 1, 3

* } 1871 Palaeozamia megaphylla Phillips, p. 169, diagram 30, ®g. 1.

} 1871 Palaeozamia longifolia Phillips, p. 169, diagram 30, ®g. 6.

1873 Yuccites Schimperianus De Zigno, p. 7, pl. 26, ®gs 1±4.

1888 Irites alaskana Lesquereux, p. 36 (one of the specimens on which this record was based was ®gured by

Fontaine, in Ward 1905, pl. 45, ®g. 5).

1889 Baeira palmata Heer; Lesquereux ( non Heer), p. 31, pl. 16, ®gs 4±5.

} 1894 Yuccites megaphylla (Phillips) Woodward, p. 598.


Figs 1, 3.

Pelourdea megaphylla (Phillips) Seward. 1, V.4652, small leaf with part of stem still attached at base of leaf;

´ 1´5. 3, near-terminal part of shoot with helically arranged leaves; ´ 1.

Fig. 2.

Pachypteris macrophylla (Brongniart) comb. nov., J.43273, holotype; ´ 2.

Fig. 4.

Carpolithes diospyriformis Sternberg, J.1152, cast of ovule; ´ 2´5.



P L A T E 1 4


} 1904 Zamites megaphyllus (Phillips) Seward, p. 110, text-®g. 11; pl. 10, ®gs 4±5; pl. 12, ®gs 1, 3±5.

1905 Nageiopsis longifolia Fontaine; Fontaine, in Ward, p. 171, pl. 45, ®gs 1±5 (®g. 2 copy of Lesquereux

1888, pl. 16, ®g. 5).

?1905

Podozamites grandifolius Fontaine; Fontaine, in Ward, p. 167, pl. 44, ®g. 1 (copy of Lesquereux 1888, pl. 16, ®g. 4).

1914 Zamites megaphyllus (Phillips) Seward: Knowlton, p. 51, pl. 7, ®g. 1.

1917 Pelourdea megaphylla (Phillips) Seward, p. 281.

} 1998 Pelourdea sp. Cleal and Rees, pls 2, 4.

Holotype . OUM J.1174, from tilestones of Stones®eld (Phillips 1871, pl. 30, ®g. 6). The specimen is re®gured here on

Plate 13, ®gure 1.

Material.

In addition to the holotype, there are 31 OUM specimens of P. megaphylla : J.1155 (holotype of Palaeozamia longifolia Phillips), J. 42625, J.43285±J.43286, J.43324, J.46262, J.54947±J.54958, J.54960±J.54969 and J.54971.

There are another 20 NHM specimens: 41380, V.86, V.3426, V.3428, V.3460, V.4063, V.4064±V.4068, V.4644,

V.4647, V.4650, V.4652, V.4661, V.4675, V.9010, V.10810 and V.12294.

Description.

Mainly isolated leaves. The largest complete example is 322 mm long and 32 mm wide (Pl. 6, ®g. 2), although there are broken fragments of what were probably larger leaves; the largest fragment is 49 mm wide. The smallest complete leaf is 55 mm long and 7 mm wide. The larger leaves are sublinguaeform with a sharply acute apex

(Pl. 6, ®g. 2; Pl. 13, ®g. 1). The taper in the distal part of the leaves is a little more on one side than the other, giving them an asymmetrical, subfalcate aspect. The widest part of the large leaves is just below half-way along their length.

In its proximal part, the leaf is more or less symmetrical about the long axis. The line of attachment at the base of the leaf is broad and concave, and usually shows a thickened edge (?abscission layer).

The smaller leaves may be sublinguaeform or have a more subtriangular aspect, with their widest point near the base

(Pl. 2, ®g. 4; Pl. 14, ®g. 1). There is not the clear-cut concave base as seen in the larger leaves. The smaller leaves instead show a constriction just above the base, but then widen to what is usually a ragged basal margin (Pl. 5, ®g. 2).

The venation consists of parallel, rarely forking veins extending along the length of the leaf. Vein density across the width of the leaf varies from 7±25 veins per cm (mean 14´2, s.d. 4´8) and is inversely correlated with leaf width.

Only one Stones®eld specimen shows leaves attached to a stem (Pl. 14, ®g. 3). This shows four leaf fragments attached to a stem 2´5 mm wide and preserved length 32 mm. There are also two other leaf fragments, one above and one below the stem, whose basal attachment is not preserved but which were probably part of the same shoot.

The most complete leaf is 56 mm long and 8 mm wide and has a sublinguaeform shape. The most proximal leaf seems to have been attached to the underside of the stem as preserved, but the compression of the sediment has twisted it round tolie along the bedding plane. The next twoleaves seem tobe attached tothe side of the stem facing the viewer (as preserved), the ®rst extending to the left side of the stem, the second to the right of the stem.

The attachment of the fourth leaf is not clearly visible, but probably was to the underside of the stem. Without knowing if all the leaves are visible (some may be embedded in the matrix, lost on the counterpart, or removed during fossilization), it is impossible to determine the phyllotaxy. However, the general pattern of attachment is clearly helical rather than pinnate.

Remarks.

Phillips (1871) used two species names for different examples of this species from Stones®eld:

Palaeozamia megaphyllus for the large, isolated leaves, and P. longifolia for the smaller leaves that he found attached to a shoot. We now know that there is a complete gradation between the two types of leaves at Stones®eld, and there can be little doubt that they all belong to the same species.

Seward (1904) assigned tothis species (with a query) Yuccites Schimperianus De Zigno, 1873, originally described from the Lower Jurassic of the Venetian Alps. The types of this Italian species are large, isolated lea¯ets, up to 42 mm wide. The largest complete example is 240 mm long (De Zigno's ®g. 2) but an incomplete leaf (his ®g. 1) was probably at least 330 mm long. The veining seems very similar to the

Stones®eld material .

In a signed manuscript note in Seward's copy of De Zigno (1873), Seward states that there were seven veins per cm, an observation that seems to have been made in Padua looking at the originals. Although this is rather low for P. megaphylla , it is in the lower part of the total range of variation that we found in the Stones®eld material .

We have, therefore, opted to follow Seward and include the

Italian material in P. megaphylla .

There have been several records of this species from the Upper Jurassic of Cape Lisburne, Alaska


(Lesquereux 1888, 1889; Fontaine, in Ward 1905; Knowlton 1914). Theyare all based on isolated leaves, which are verysimilar in shape and venation to the Stones®eld material .

In particular, when the base is preserved, it is usuallyconcave, indicating that the leaves originallyclasped the stem. Fontaine ( in Ward

1905) regarded them as conspeci®c with Nageiopsis longifolia Fontaine, 1889 from the Potomac ¯oras of the USA, but the types of the latter all have a markedly constricted base more reminiscent of Podozamites .

Arber (1907, 1909) and Wills (1910) described some verysimilar plant remains from the Triassic of the

English Midlands as Zamites grandis Arber. There are manypoints of similaritybetween these Triassic specimens and P. megaphylla , including the helical arrangement of the leaves around the branch.

Compared with the Stones®eld species, however, the Triassic leaves do not have such a graduallytapered apex. In manyof the Triassic leaves, the base is clearlyconstricted, whereas most Stones®eld leaves are broadlyattached; onlythe smallest of the Stones®eld leaves are constricted above the base. We therefore regard this Triassic material as a distinct species of Pelourdea , for which we propose the new combination

Pelourdea grandis (Arber) (basionym Zamites grandis Arber, 1907).

Signi®cantly, no comparable leaves or leafy shoots are known from the Yorkshire Jurassic ¯ora. The specimens described byHarris et al.

(1974, p. 135) as Desmiophyllum are much more slender and have little in common with Pelourdea .

The larger leaves, which are byfar the commonest at Stones®eld, have what seems to be a de®nite abscission zone at the base, suggesting that theyhad been shed bythe plant. The smaller leaves, in contrast, show a near-basal constriction, which might have marked an incipient abscission zone, but was not where the leaf was detached from the stem. These smaller leaves were presumablynot, therefore, shed bythe plants but were torn awaybysome traumatic process.

In the absence of reproductive structures, it is impossible to be sure of the af®nities of this plant. Its inclusion in Pelourdea rather than the bennettite morphogenus Zamites is based largelyon the spiral mode of attachment of the leaves. The apparent presence of an abscission layer at the base of the larger leaves is also evidence that it is not bennettitalean.

?

Pelourdea sp. (seedling)

Text-®gure 3 B

Material.

OUM J.43278.

Description . A (?)shoot preserved for a length of 170 mm, with a main axis 1´5 mm wide at its base. Slender (?)leaves are widelyspaced in a helical arrangement. The (?)leaves are decurrent at the base and then recurved at more distal positions. The (?)leaves are slender and parallel-sided, less than 1 mm wide. The longest (?)leaf is 65 mm long.

Remarks . This is unique among the Stones®eld specimens and probablyrepresents a leafyshoot. The nearest comparison is with Triassic specimens that have been interpreted as seedlings of the herbaceous conifer Aethophyllum stipulare Brongniart (Grauvogel-Stamm 1978, pl. 15; Rothwell et al.

2000, pl. 1,

®g. 3). There is no evidence at Stones®eld of mature Aethophyllum plants and we do not suggest that our specimen belongs there. However, leaves of mature Aethophyllum have a passing resemblance to small

Pelourdea leaves. We therefore tentativelysuggest that this mayhave been part of a seedling of the

Pelourdea -bearing plant.

Genus

CARPOLITHES

Linnaeus ex Sternberg, 1823

Remarks . Numerous isolated ovules occur at Stones®eld and show a range of morphologies. Seward

(1904) recognized this variabilitybut still assigned them to a single species, Carpolithes diospyriformis .

Having examined these ovules carefully, we feel we can now recognize two distinct morphologies. One has a verydistinctive shape, corresponding to the original C. diospyriformis . The other, although clearly different, has fewer distinctive characters and so we have referred to it just as Carpolithes sp.

In the following descriptions, we refer to these fossils as ovules, although we recognize that there is no evidence as to whether or not theywere fertilized.


Carpolithes diospyriformis Sternberg, 1823

Plate 14, ®gure 4; Plate 15, ®gures 2±3

* } 1823 Carpolites diospyriformis Sternberg, p. 37, pl. 37, ®g. 6.

?

} 1825 Carpolites morchellaeformis Sternberg, p. 37, pl. 37, ®g. 3.

} 1871 Carpolithus diospyriformis Sternberg; Phillips, p. 171, diagram32, ®g. 2.

} 1904 Carpolithes diospyriformis Sternberg; Seward, p. 128, pl. 12, ®g. 1; pl. 13, ®g. 7.

Holotype . OUM J.55980 (Pl. 15, ®g. 2) (in error, KvacÏek and StrakovaÂ 1997 recorded it as J.1151). It originated from

Stones®eld.

Material.

In addition to the holotype, there are 14 OUM specimens: numbers J.1151 (part and counterpart),

J.1152±J.1153, J.43303±J.43307, J.43312, J.43320±J.43321, and MM.483. The NHM has 29 specimens: 40514

(two specimens), 41168, 52866 (ten specimens), 52938, V.82 (two specimens), V.2513 (seven specimens), V.4648,

V.4663, V.6347, V.6582, V.6590, and V.35711. A number of the latter specimens are labelled as coming from Ènslow

Bridge', which is c.

9 km east of Stones®eld, but is assumed to be from the same stratigraphical level.

Description.

Casts of isolated pyriform ovules, 18±32 mm long and 11±18 mm wide. Their widest part is about one-quarter of the way up fromthe base, fromwhich they gradually taper to a narrow apex (Pl. 14, ®g. 4; Pl. 15, ®g. 3).

Although suffering from some compression, the ovules seem to be platyspermic, but without any sign of lateral wings

(Pl. 15, ®g. 2). Where there is both cast and mould preserved, there is a signi®cant cavity between them, suggesting there was originally a ¯eshy integument. The nucellus shows a short `stalk' at the base but none is visible on the outer preserved surface of the ovule (Pl. 15, ®g. 2).

Remarks.

These are the commonest ovules found in the Stones®eld ¯ora and are clearly conspeci®c with the holotype ®gured by Sternberg. Their af®nities are unknown as there is no evidence of attachment. If they are platyspermic, it is unlikely that they will belong to either the Cycadales or Bennettitales. The

Caytoniales have platyspermic ovules, but they are normally much smaller, and the ovules associated with

Sagenopteris colpodes in the Yorkshire Jurassic (Harris, 1964) certainly bear no resemblance to

C. diospyriformis . Conifer ovules also, although platyspermic, are rarely this large. More similar are the ovules of some ginkgoaleans. Ginkgoalean foliage is quite rare at Stones®eld but biostratinomic sorting could explain why the ovules are far more common. However, if relative abundance is taken into account, it is notable that the ovules of the commonest megaphyllous foliage ( Pelourdea ) are unknown, and C. diospyriformis is the commonest species of ovule.

Seward (1904) claimed that the stalk of these ovules was not centrally attached to the base of the ovule, but offset to the side. This was based on two specimens. One of these (V.2513b; ®gured by Seward 1904, pl. 12, ®g. 7) shows what seems to be an offset scar fromwhere it was abscissed froma stalk. However, the ovule is much smaller than the normal C. diospyriformis and we regard it as belonging to a different species. The second specimen (V.2513; ®gured by Seward 1904, pl. 13, ®g. 7) is more typical in size and shape for C. diospyriformis , but the offset `stalk' is not convincing. When viewed closely, however, the

`stalk' appears to be merely a piece of matrix that was not an integral part of the ovule.

Similar detached ovules have been found at the Osmington Mills site, from where Stockey (1980) described Araucaria brownii Stockey (P. Davies, pers. comm. 2001). However, both C. diospyriformis and


Fig. 1.

Komlopteris speciosa (Ettingshausen) comb. nov., J.43277, part of middle of leaf, with very elongate pinnules;

´ 1´5.

Figs 2±3.

Carpolithes diospyriformis Sternberg. 2, J.1151/J1151a, holotype, preserved as cast and mould; ´ 2. 3, cast showing evidence of integument in distal part; ´ 2´5.

Fig. 4.

Phyllites sp., BMNH 41385, angiosperm-like leaf; ´ 1´25.



P L A T E 1 5

790 P A L A E O N T O L O G Y , V O L U M E 4 6 the new Osmington Mills ovules are signi®cantly larger than those in Stockey's cones, the latter being more comparable with Araucarites brodei (see earlier in this paper).

Carpolithes sp.

Plate 7, ®gure 3

} 1904 Carpolithes diospyriformis Sternberg; Seward ( non Sternberg), pl. 12, ®g. 7; pl. 13, ®g. 6.

Material.

NHM V.2513a, V.2513b and V.4649.

Description . Small ovoid ovules, 11 mm long and 7±11 mm wide, with a slightly protruding micropyle. One specimen

(Pl. 7, ®g. 3) is preserved as a cast and mould, with a wide gap between them presumably representing the integument.

Both this and another specimen that is just a cast (V.2513b) shows what appears to be an attachment scar at its chalazal end. This scar is offset from the long axis of the ovule.

Remarks.

Seward (1904) discussed the possibility that these small ovules might be a separate species from

C. diospyriformis . He eventually decided they were the same species largely because of the laterally offset attachment scar, which he thought was also present in C. diospyriformis . As remarked above, however, we believe the laterally offset stalk that Seward believed he had seen in C. diospyriformis is a taphonomic effect. In view of the marked difference in size and shape of these ovules, we have placed them in a separate species.

Genus PHYLLITES Brongniart, 1822

Remarks . This morphogenus is now used mainly for entire leaves of uncertain af®nities.

Phyllites sp.

Plate 15, ®gure 4; Text-®gure 5

} 1904 Phyllites sp. Seward, p. 152, pl. 11, ®gs 5±6.

} 1998 Phyllites sp. Cleal and Rees, pl. 6.

Material . NHM 41385 and V.85, which are part and counterpart of the same leaf.

Description . A wide elliptical leaf, 36 mm long and 23 mm wide, with a bluntly acuminate apex and a decurrent base.

The stalk is preserved for a length of c.

7 mm beyond the leaf base. Leaf margin entire. Venation is actinodromous, with three primary veins radiating from a point just above the leaf base. The central primary appears to extend to the leaf apex although the upper part of the leaf is rather poorly preserved. The lateral primaries curve slightly in their upper regions and appear to meet the leaf margin c.

8 mm from the apex. One lateral primary shows two or possibly more secondaries on its outwards facing side. The secondaries diverge narrowly from the primary, at c.

35 8 in the lower part of the leaf, increasing to c.

45 8 at more distal levels. Higher level veins not preserved.

Remarks.

This remarkable fossil clearly caused Seward (1904) considerable dif®culties when he ®rst described it. As he wrote, `Had the specimen been found in rocks known to contain the remains of

Angiosperms, there would be no hesitation in identifying it as a leaf of a Dicotyledon' (p. 153). One explanation considered by Seward was that the leaf did not in fact come from Stones®eld but, for both curatorial and lithological reasons, he dismissed this option. We have taken this a step further, by having a thin section of the matrix prepared (courtesy of C. H. Shute, NHM) and this is fully compatible with the other fossils from Stones®eld. We can ®nd no reason to disbelieve the record in original registers of NHM, that the fossil originated from Stones®eld.

Another explanation considered by Seward (1904) was that it was the leaf of another group of plants, such as the ferns. It is true that some Mesozoic ferns (e.g.

Dictyophyllum ) and gymnosperms (Caytoniales, some cycads and bennettitaleans) show reticulate veining. However, the possibility of angiosperm


TEXT-FIG.

5.

Phyllites sp., Stones®eld Slate, Stones®eld, Oxfordshire.

A , BMNH 41385, complete leaf showing petiole;

´ 2.

B , V.85, counterpart, not showing petiole, but with remnants of venation more clearly preserved; ´ 3.

af®nities for this leaf is not based on reticulate veining, the high order veins not being preserved. Rather, it is suggested by its apparently actinodromous primary veins.

The af®nities of this leaf must obviously remain in doubt, due to its relatively poor preservation, and the absence of any anatomy or reproductive structures. However, the age of the fossil is becoming less of a problem with it having angiosperm af®nities. The recent discovery of a fully-¯edged angiosperm fruiting structure in the basal Cretaceous or Upper Jurassic of China (Sun et al.

1998) has further closed the gap between the Stones®eld fossil and the earliest unequivocal angiosperm. In our view, the likelihood must be that, if this is not the leaf of an early angiosperm, it is from a gymnosperm ancestor that had already developed many of the foliar characters of the angiosperms.

D I S C U S S I O N

Palaeoecological interpretation

Being preserved in marine deposits, the Stones®eld ¯ora is probably in part the remains of vegetation that grew on the coastal slopes surrounding the marine basin in southern England (Text-®g. 1). There may also be some remains of plants from ùpland' vegetation, especially if they had durable leaves that could withstand long-distance transportation. The prevalence of cheirolepidiacean conifer remains suggests that forests of these trees occupied large areas of these coasts. Some Early Cretaceous cheirolepidiaceans may have been adapted to a wider range of habitats including non-saline conditions (Alvin 1982). In the


Jurassic, however, such as in the upper Portlandian deposits of southern England, the evidence suggests they mainly favoured lowland, salt-affected coastal habitats that suffered periodic water-stress (Francis

1983). The commonest of the cycadophyte fossils is the slender-lea¯eted Ptilophyllum , which Krassilov

(1975) suggested might have been a mangrove-like plant during the Middle Jurassic, growing on the coastal margins where they would periodically be inundated by sea-water. The third common component of the Stones®eld ¯ora ( Pelourdea ) is of unknown habitat-preference but, from its other occurrences, probably favoured relatively well-drained substrates. Plants thought to favour freshwater, wetland habitats

(sphenophytes, ferns, czekanowskialeans, ginkgoaleans) are all but absent. One factor may have been that these plant groups tend to have more delicate foliage with less robust cuticles, making them less able to withstand transportation. However, these groups are found in the Kimmeridgian ¯oras of Scotland (van

Konijnenburg-van Cittert and van der Burgh 1996) which are preserved in a similar marine setting to

Stones®eld and in some cases (e.g. Culgower) are in a similar coarse matrix. This suggests that wetland habitats were not a dominant feature of coastal regions of southern England.

We therefore envisage the area surrounding the marine basin in southern England being fringed by a belt of coastal vegetation consisting mainly of Ptilophyllum -bearing bennettitaleans. Behind this were lowlands with mainly conifer forests (cheirolepidiaceans and araucariaceans). These lowlands were either well drained or periodically affected by sea-water, the almost complete absence of plants indicating saltmarsh conditions (e.g.

Hausmannia , Pachypteris lanceolata ) perhaps suggesting the former.

Comparison with other ¯oras

The ¯oras found in the stratigraphically older Charlbury Formation of Gloucestershire (Eyeford and

Sevenhampton Common) occur in a very similar facies to that at Stones®eld. Neither of the Gloucestershire ¯oras has been subjected to detailed systematic analysis for over a century, although Seward (1904) included some specimens in his Stones®eld study. A list of the plants collected by the local amateur,

Edward Witts, is given by Savage (1961), although it does not say on whose authority the identi®cations are based. Based largely on the records in Seward (1904), a comparison between the Stones®eld and

Gloucestershire ¯oras is given in Table 2. The most obvious fact brought out by this analysis is that the

Stones®eld ¯oras appears far more diverse (with 25 species), Eyeford only having 12 recorded species and

Sevenhampton eight. However, this may be mainly due to the absence of modern systematic work on the Gloucestershire ¯oras. The most notable point of comparison is the abundance at all three of

Brachyphyllum expansum , although there are no reports of cones from the Gloucestershire sites to con®rm they are foliage of the same conifer-types. The distinctive bennettite frond Sphenozamites bellii is also known from all three sites. However, Ptilophyllum pectiniformis has not been reported from the

Gloucestershire ¯oras and, in view of its abundance at Stones®eld, this absence must be regarded as signi®cant. There are also taxa in the Gloucestershire ¯oras that are unknown from Stones®eld, most notably Ginkgo digitata , Podozamites stones®eldensis and Carpolithes conicus . Clearly, a detailed comparison must await a systematic revision of the Gloucestershire ¯oras, but the presently available evidence does not support the view of Seward (1904) that they are essentially indistinguishable ¯oras.

An anatomically preserved ¯ora has recently been reported from marine Middle Jurassic sediments on the Isle of Skye, Scotland (Bateman et al.

2000; see also Cleal et al.

2001). The Skye ¯ora is dominated by mainly araucariacean conifers, rather than cheirolepidiaceans as seem to dominate the Stones®eld ¯ora.

Ptilophyllum occurs on Skye and an entire-leafed cycad. However, ferns are more diverse in the Skye ¯ora compared with Stones®eld, with four or ®ve species having been identi®ed. Also present is a rhizome that belongs to the sphenophytes, a group unknown in the Stones®eld ¯ora.

Brongniart (1828 a ) was the ®rst to suggest the similarity between the Stones®eld and Yorkshire Jurassic

¯oras, a view that seems to have become well established. It is dif®cult to make a coherent comparison between a ¯ora like that of Stones®eld, containing a mere 27 species, and the more than 200 species of the

Yorkshire ¯ora. An important point is that the Yorkshire `¯ora' in fact represents many ¯oras collected from many different localities and horizons, whereas the Stones®eld ¯ora is from just one locality and horizon. Furthermore, Stones®eld has yielded far fewer specimens than most of the Yorkshire localities, and many rare species in the original vegetation will, therefore, tend not to be represented in the


TABLE

2. Comparison of Middle Jurassic ¯oras from Stones®eld, Eyeford and Sevenhampton (not including some of the unnamed species known from Stones®eld but not the other localities).

Eyeford Sevenhampton cf.

Ptilophyllum pectiniformis

Ptilophyllum

Sphenozamites bellii

Weltrichia

Taeniopteris vittata

Conites bucklandii

G. digitata

Brachyphyllum expansum

Elatocladus

Podozamites stones®eldensis

Masculostrobus

Classostrobus

Araucarites brodiei

Pelourdea megaphylla

Carpolithes diospyriformis

C. conicus

C.

Dictyophyllum

Phyllites aff.

sp.

sp.

cf.

cf.

sp.

sp.

sp.

Phlebopteris woodwardii cf.

Coniopteris sp.

Sagenopteris colpodes

Pachypteris macrophylla

Komlopteris speciosa cf.

Ctenozamites leckenbyi

Ctenis

Ctenis

Ginkgo sp.

cf.

sp.

sulcicaulis hirsutum longifolius

(Brongniart) Heer laxus

Lindley and Hutton

X

X

X

X

X

X

X

X

X

Stones®eld

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X?

X

X

X

X

X

X

Oxfordshire fossil ¯ora. The poor representation of ferns at Stones®eld is maybe because their relatively delicate fronds could not normally withstand signi®cant transportation. However, other absentees from

Stones®eld are less easily explainable, such as the horsetails. According to Harris (1961 a ), Equisetum is one of the most abundant recognizable fossils in the Yorkshire Jurassic ¯ora and its stems are suf®ciently robust to be able to withstand considerable transportation. Their absence from Stones®eld must re¯ect the absence of the type of marshy conditions occupied by most Mesozoic horsetails. Ginkgoalean foliage is often common in the Yorkshire Jurassic (Harris et al.

1974), partly because it is deciduous, but is represented at Stones®eld by just a single poor specimen.

More signi®cant are the taxa found at Stones®eld but not in Yorkshire. Most signi®cant here is

Pelourdea , which is one of the most abundant leaf-types at Stones®eld, but which has never been discovered at Yorkshire. The (relatively) abundant ovules at Stones®eld called Carpolithes diospyriformis also have no equivalent in Yorkshire.

Komlopteris is so far unreported from Yorkshire, although it is similar to species such as Pachypteris papillosa that are common there. Similarly, the apparent rarity of

Sphenozamites in Yorkshire may have to be reconsidered in the light of its similarity with Otozamites .

Vakhrameev (1991) suggested that two types of Early and Middle Jurassic vegetation could be recognized in Europe. This was mainly based on observations on Early Jurassic ¯oras, but his observations can be related to Middle Jurassic ¯oras. Early Jurassic vegetation from moister habitats is epitomized by the Bavarian ¯oras, which include abundant equisetaleans, ferns and caytonialeans (Weber 1968).

Conifers are relatively rare and consist mainly of large-leafed forms such as Podozamites . This bears

794 P A L A E O N T O L O G Y , V O L U M E 4 6 some comparisons with many of the ¯oras from the Yorkshire Jurassic. The Yorkshire ¯oras contain what appear to be a much broader range of plant groups, but this may in part be due to the extensive collecting that has taken place at these extensive natural exposures.

The second of Vakhrameev's (1991) vegetation types favoured drier slopes adjoining marine basins and is thus most often preserved in marine sediments. This is epitomized in the Lower Jurassic fossil record by the Venetian Grey Limestones ¯ora of northern Italy (De Zigno 1856±67, 1873±85; Grandori 1913;

Wesley 1956, 1958, 1966, 1974). This has relatively rare ferns, equisetaleans and caytonialeans, and

Ginkgo is all but absent. Instead, there are abundant small-leafed conifers, corystospermaceans, and bennettitaleans. This is clearly more similar to the Stones®eld ¯ora (and those of the Cotswold `Slates' and

Skye). The comparison is further strengthened by the bennettitaleans, including abundant Ptilophyllum and Sphenozamites , and the presence of leaves evidently belonging to Pelourdea .

There are two areas in Britain that have yielded well-preserved evidence of Late Jurassic vegetation. In southern England, especially around the Isle of Portland in Dorset, petri®ed remains of conifer and bennettitalean trunks are known from the latest Jurassic (reviewed by Cleal et al.

2001). Francis (1983,

1984) has interpreted them as representing vegetation growing in a semi-arid environment adjoining the sea. A detailed comparison with Stones®eld is hindered by the virtual absence of foliage remains from

Portland, but the general aspect of the two ¯oras is comparable.

Other British Late Jurassic ¯oras are from the Kimmeridgian of north-east Scotland, such as Culgower and Lothbeg Point (reviewed by van Konijnenburg-van Cittert and van der Burgh 1996 and Cleal et al.

2001). As with the Stones®eld ¯ora, these Scottish ¯oras are mainly preserved as small fragments preserved in marine deposits. Some, such as Culgower, are also preserved in a coarse matrix, although others, such as Lothbeg, are in ®ner-grained sediment and thus tend to show ®ner surface detail and often have cuticles. Conifers are abundant in both the Stones®eld and Scottish ¯oras. The latter do not seem to be dominated by cheirolepidiaceans as Stones®eld appears to be, although the dif®culty of establishing the family af®nities of isolated sterile foliage makes it dif®cult to be certain of this. What is clear, however, is that the Scottish ¯oras contain abundant ferns, including at Culgower, where the coarser matrix might have been expected not to favour the preservation of ferns. Particularly abundant are forms thought to have inhabited saltmarshes, such as Hausmannia and Gleichenites . They also include abundant czekanowskias,

Sagenopteris and Pachypteris , which are either absent or very rare at Stones®eld. Bennettitaleans occur in the Scottish ¯oras but they do not form such a large proportion of the ¯ora as at Stones®eld, and the dominant morphogenus in the latter ( Ptilophyllum ) appears to be absent.

Pelourdea is unknown from

Scotland. Part of this marked difference between the Stones®eld and Scottish ¯oras is that the latter are dominated by riparian vegetation that had drifted down-river into the sea (van Konijnenburg-van Cittert and van der Burgh 1996). The coastal vegetation in Scotland also seems to have been quite different, being dominated by herbaceous saltmarsh vegetation.

There is also some comparison between the Stones®eld ¯ora and Oxfordian±Kimmeridgian ¯oras from

France, preserved in marine deposits (Barale 1981). There is no evidence of Pelourdea or any comparable foliage in the French ¯oras, but cheirolepidiacean conifer remains are common. Some of the foliage appears indistinguishable from Brachyphyllum expansum , although the associated cones ( Masculostrobus dorchensis Barale) are more elongate than those found at Stones®eld. No Ptilophyllum was reported from the French ¯oras, but some of the Zamites present [e.g.

Z. feneonis (Pomel) Ettingshausen, Z. pumilo de

Saporta] have very slender lea¯ets and may conceivably have occupied a similar ecological niche.

Pachypteris desmomera from near Lyon is very similar to (possibly conspeci®c with) the Stones®eld species P. macrophylla . According to Barale, the French ¯oras represent vegetation from temporarily emergent, coastal habitats and may include mainly halophile plants.

Based on these comparisons, it is clear that depositional environment is only part of the explanation for understanding the differences between these ¯oras. If it was the overriding factor, the Scottish ¯oras should be far more similar to the Stones®eld and southern Europe ¯oras. A more important factor may have been climate. A recent global study of Jurassic phytogeography by Rees et al.

(2000) suggests that two biomes can be recognised in western Europe, re¯ecting differences in the prevailing climate. A warm temperate biome is represented by the Yorkshire and Scottish ¯ora, while a seasonally dry biome is represented by the Stones®eld, French and Italian ¯oras. This is consistent with the detailed differences

C L E A L A N D R E E S : M I D D L E J U R A S S I C F L O R A 795 discussed above, with plants such as ferns and horsetails being far more common in the wetter warmtemperate regions, and microphyllous conifers more dominant components of the seasonally dry regions.

Acknowledgements . The paper is based mainly on the collections in The Natural History Museum, London, and the

Oxford University Museum, to whose authorities we are very grateful for allowing access to their collections. The help provided at those institutions by C. H. Shute, T. Foster and P. G. Davis (NHM), and P. Powell (OUM) is especially acknowledged. The illustrations in this volume are nearly all based on photographs by P. Crabb (NHM), and J. Cooke and R. Hall (OUM), to whom we are deeply indebted. The photographs of Brachyphyllum cuticles were taken by CJC and printed by the Photographic Department, National Museums and Galleries of Wales, Cardiff. Thanks go to

J. KvacÏek, C. H. Shute, C. R. Hill, W. A. Wimbledon, K. L. Alvin and G. Zijlstra for their helpful comments and advice on various aspects of the study. Finally, we are greatly indebted to Han van Konijnenburg-van Cittert for constructively reviewing the manuscript and making numerous helpful suggestions and corrections.

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Typescript received 16 October 2001

Revised typescript received 30 April 2002

C. J. CLEAL

Department of Biodiversity and Systematic Biology

National Museums and Galleries of Wales

Cathays Park, Cardiff CF10 3NP, UK e-mail chris.cleal@nmgw.ac.uk

P. A. REES

Department of the Geophysical Sciences

University of Chicago

5734 South Ellis Avenue

Chicago Il60637, USA e-mail rees@geosci.uchicago.edu

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