IAWA Journal, Vol. 32 (4), 2011: 521–530
A NEW LATE CRETACEOUS (CONIACIAN-MAASTRICHTIAN)
JAVELINOXYLON WOOD FROM CHIHUAHUA, MEXICO
Emilio Estrada-Ruiz1 and Hugo I. Martínez-Cabrera2
SUMMARY
We describe a new fossil wood from the San Carlos Formation
(Coniacian-Maastrichtian) in Chihuahua, northern Mexico. This Malvaceae
s.l. wood is diffuse porous, vessels are solitary and in radial multiples,
simple perforation plates, small alternate intervessel pits, vessel-ray
parenchyma pits that are rounded with reduced borders, septate and
nonseptate fibers,homocellular and heterocellular rays, and storied rays and
vessel elements. These features support its inclusion within the genus
Javelinoxylon, Malvaceae s.l., which occurs in other Upper Cretaceous
localities in northern Mexico (Olmos Formation) and Texas (Aguja and
Javelina Formations). This San Carlos fossil wood is the earliest occurrence
of storied structure in the fossil record and the earliest angiosperm record for
the State of Chihuahua, Mexico.
Key words: Late Cretaceous, wood anatomy, Malvaceae s.l., San Carlos
Formation, Chihuahua, Mexico.
INTRODUCTION
Northern Mexico is a promising region for fossil wood studies because it can provide
information about Cretaceous angiosperms at lower latitudes of the Western Interior of
North America. These Mexican Cretaceous florascan be compared with florasfrom higher
latitudes and help with developing an understanding of biogeographic variation. The
formations in northern Mexico (Estrada-Ruiz et al. 2007, 2010) are located near diverse
assemblages of Cretaceous angiosperm fossil woods in Texas (Wheeler & Lehman 2000,
2009). In northern Mexico there are a large number of Late Cretaceous localities bearing
a relatively high diversity of angiosperm and gymnosperm fossil woods, but only a few
species have been described. Cevallos-Ferriz (1983) recognized a Late Cretaceous wood
from Sonora with characters suggestive of Canarioxylon (later considered to be closer to
Paraphyllanthoxylon [Gryc et al. 2009]). The upper Campanian-lower Maastrichtian strata
of the Olmos Formation deposited into the Sabinas Basin, Coahuila State, Mexico, have
several angiosperm woods including cf. Paraphyllanthoxylon (Cevallos-Ferriz & Weber
1992), and others with relationships to modern families of varying certainty
(?Anacardiaceae, ?Burseraceae, Cornaceae, ?Fagaceae, cf. Lauraceae). One of the
1) Department of Biology, Texas State University, 601 University Drive, San Marcos, TX 78666,
U.S.A. [E-mail: emilkpaleobot@yahoo.com.mx or ee20@txstate.edu].2) Department of Ecology
and Evolutionary Biology, University of Connecticut, 75 North Eagleville Road, Unit 3043,
Storrs, CT 06269-3043, U.S.A. [E-mail: hugo.martinez_cabrera@uconn.edu].
IAWA Journal, Vol. 32 (4), 2011522
most important families in the region, given the number of records, is Malvaceae s.l.
(Estrada-Ruiz et al. 2007, 2010). Malvaceae s.l. (which includes Bombacaceae,
Sterculiaceae, and Tiliaceae; APG III, 2009) is a family that has around 4,300 species,
distributed in temperate and warm regions, and is also an important element of the
tropical rainforest (Bayer & Kubitzki 2003). The fossil record of Malvaceae s.l. is
diverse with a large geographic and stratigraphic span. Leaves attributed to Bombax
(Cretaceous to Tertiary), Byttneriophyllum (Neogene), Cola (Late Oligocene), Sterculia
(Eocene to Oligocene) and Byttneriophyllum, Dombeyopsis and Laria (Neogene) (e.g.,
Givulescu 1970; Kvacek & Wilde 2010; Worobiec et al. 2010) have been reported.
There are also records of reproductive structures, e.g., Florissantia, Cantitilia (Eocene),
Daberocarpon (Cretaceous), Sterculia (Oligocene), Byttneriopsis and Craigia
(Oligocene to Miocene), Reevesia (Miocene) (e.g., Kvacek et al. 1991; Manchester
1992; Mehrota 2000; Kvacek 2006; Kvacek & Wilde 2010). Fossil woods of Malvaceae
s.l. have been reported from several parts of the world including North America,
Europe, Africa and Asia, see Gregory et al. (2009). In this paper we describe a new
species of Javelinoxylon from the San Carlos Formation. This record represents the
earliest stratigraphic occurrence of Javelinoxylon as well as the earliest occurrence of
storied structure. The identificationof a new species of Javelinoxylon extends our
knowledge of the Late Cretaceous flora of Mexico and offers hints on the possible
relationships with foras from other localities in the Western Interior of North America
during the Late Cretaceous.
D.E.C.A.
Parque
Cretácico A.C.
locality
Juan
Aldama
Chihuahua
Figure 1. Location of the fossiliferous outcrop. – A: Map of Mexico. – B: Map of Chihuahua state.
523
Estrada-Ruiz & Martínez-Cabrera — Javelinoxylon from Mexico
Figure 2. Stratigraphic column of the D.E.C.A. Parque Cretácico, A.C. locality, San Carlos Formation. (Courtesy of Dr. Jesús Alvarado, Institute of Geology, UNAM.)
MATERIALS AND METHODS
The fossil wood specimens studied were collected from a single locality in an outcrop of
the San Carlos Formation. The locality is within the D.E.C.A. (Daniel Eduardo/ David
Ernesto Carrillo Acosta) Parque Cretácico A.C., which is located approximately 55 km
east of Juan Aldama town, Aldama Municipality, Chihuahua, Mexico (28° 51 ' 45 " N and
105° 24' 05" W) (Fig. 1). The area under study has different fossiliferous outcrops that
contain plants, bivalves, gastropods, ammonites, and dinosaur bones (Ernesto Carrillo,
personal comm. 2010). Many of the wood specimens in the outcrop are in situ, some of
the woods are in growth position and are up to 10 m long. The samples described here,
however, are not in situ and are less than 16 cm long (Fig. 2).
GEOLOGICAL SETTING
Hernández-Noriega et al. (2000) mapped the area where the woods studied here were
collected. These authors found that the oldest Cretaceous strata that outcrop in this area
belong to the formations Las Vigas (Neocomian), Del Rio (Upper Albian–Lower
IAWA Journal, Vol. 32 (4), 2011524
Cenomanian), and Buda (Upper Cenomanian). We found the geology in the area to be
complex and requiring additional study. Overlying these Cretaceous strata there are
Oligocene rhyolitic tuffs (unnamed), and Miocene polymictic conglomerates and basalt- ic
spills, as well as wide spread Quaternary silts on the top of the sequence. According to
Hernández-Noriega et al. (2000) the contact between the Buda Formation and San Carlos
Formation (Coniacian-Maastrichtian) is not seen in the studied area but they show that
on the top of this latter formation there are oligomictic conglomerates (unnamed). During
the paleontological prospecting within and around the D.E.C.A. Park area, the fossil
woods were collected with dinosaur bones from strata of green and yellow sandstone with
parallel and cross laminations and paleochannels of up to 1 m long, which here are
interpreted as part of the San Carlos Formation. On the top of these sands there are
conglomerates that also bear dinosaur bone remains, which correspond to those
conglomerate strata on the top of the San Carlos Formation mapped by HernándezNoriega
et al. (2000). Below the fossil wood-bearing strata there are calcareous clays with
abundant invertebrate fossils, including bivalves, gastropods and ammonites. A
preliminary taxonomical analysis on these ammonites by Dr. González-Arreola (personal
comm. 2011) and her students shows the occurrence of a Barremian-Turonian assemblage
that includes Mortoniceras, Brancoceras, Prionocyclus, Coillopoceras, Acanthoceras,
Acompsoceras, Romaniceras, Mammites, Pseudothurmannia, which suggests a
post-Turonian age of the fossil wood-bearing strata recognized here as the San Carlos
Formation. Transverse, tangential and radial sections of wood were obtained using the
standard thin section technique. The descriptions use terminology from the IAWA
Hardwood List (IAWA Committee 1989). Affinitieswere determined by consulting the
literature (e.g., Metcalfe & Chalk 1950; Détienne & Jacquet 1983; Ilic 1987, 1991), and
by performing searches on InsideWood, a wood identification database web site (Inside
Wood 2004-onwards; Wheeler 2011). The specimens described herein are housed in the
National Paleontological Collection, Institute of Geology, Universidad Nacional
Autónoma de México (UNAM).
DESCRIPTION
Wheeler, Lehman & Gasson 1994 (Malvaceae s.l.) Javelinoxylon deca
Estrada-Ruiz & Martínez-Cabrera, sp. nov. (Fig. 3) Diagnosis — Growth rings indistinct,
woods diffuse porous, vessels solitary and in radial multiples of 2–7, some vessels in clusters,
simple perforation plates, alternate intervessel pits, vessel-ray parenchyma pits rounded and of
a single type, axial parenchyma scanty paratracheal and apotracheal diffuse, septate and
non-septate fibers,rays homocellular and heterocellular, vessel elements and rays storied.
Description — This description, and means of the quantitative characters, is based on two
specimens. Growth rings indistinct. Wood diffuse porous, vessels are solitary (25%) and in
radial multiples of 2 (3 [7]), oval in outline with 16.5 (9–26) vessels/mm (Fig. 3A, B). Some
vessel clusters are
2J a v e l i n o x y l o n
525
Estrada-Ruiz & Martínez-Cabrera — Javelinoxylon from Mexico
Figure 3. Light micrographs of Javelinoxylon deca holotype – A: Transverse section (TS). Diffuse
porous. – B: TS. Scanty paratracheal axial parenchyma (arrows). – C: Radial longitudinal section
(RLS). Simple perforation plate (PP). – D: Tangential longitudinal section (TLS). Storied
multiseriate rays. – E: RLS. Vessel-ray parenchyma pits with circular shape (arrows). – F: TLS.
Alternate intervessel pits. – G: RLS. Heterocellular rays. — Scale bar = 300 µ m in A, 130 µ m in B
& C, 335 µ m in D, 30 µ m in E, 17 µ m in F, 70 µ m in G.
also present, the vessels have a mean tangential diameter of 123 (80–200) µ m, and a
mean vessel element length of 226 (310–500) µ m. Simple perforation plates (Fig. 3C).
Vessels have abundant thin-walled tyloses (Fig. 3D) and dark contents and small
alternate intervessel pits with aperture diameter of 5 (4–6) µ m (Fig. 3F). Vessel-ray and
vessel-parenchyma pits are rounded and with reduced borders (Fig. 3E). Vessel
elements are storied in some regions. Axial parenchyma apotracheal diffuse and
occasionally scanty paratracheal (Fig. 3B). Fibers are both septate and non-septate,
with thin to thick walls. Heterocellular and homocellular rays, 1–4 cells wide,
triseriate rays are common, rays are storied in some regions (Fig. 3D), homocellular
rays are composed of procumbent
IAWA Journal, Vol. 32 (4), 2011526
cells and heterocellular rays are composed of procumbent cells in the body with one row
of erect cells in the margins (Fig. 3G). Multiseriate rays are 562 (216–1176) µ m high and
65 (32–100) µ m wide. Holotype designated here: National Paleontological Collection,
Institute of Geology, UNAM. IGM-PB 374 (wood specimen, c. 9 cm in diameter and c. 7
cm long). IGM-LPB 966-977 (slides with thin sections). Paratype: National
Paleontological Collection, Institute of Geology, UNAM. IGMPB 584 (wood specimen, c.
1.5 cm in diameter and c. 16 cm long). IGM-LPB 978-991 (slides with thin sections).
Etymology: The specific epithet refers to D. E. C. A. Parque Cretácico, where the wood
was collected. Horizon: Upper Cretaceous, Coniacian-Maastrichtian, San Carlos
Formation .
DISCUSSION
Comparison to fossil plants The combination of characters seen in this San Carlos
wood (diffuse porous, vessels solitary and in radial multiples, simple perforation plates,
alternate intervessel pits, vessel-ray parenchyma pits rounded with reduced borders,
septate and non-septate fibers and heterocellular rays, are found in Paraphyllanthoxylon
and Javelinoxylon (e.g., Wheeler et al. 1994, 1995; Estrada-Ruiz et al. 2007; Wheeler &
Lehman 2009). Javelinoxylon deca and Paraphyllanthoxylon share some characters
such as diffuse porosity, simple perforation plates, alternate intervessel pits, vessel-ray
parenchyma pits with reduced borders, septate fibersthat lack distinctly bordered pits
and heterocellu- lar multiseriate rays (Wheeler & Lehman 2009). However, the
presence of storied structure and homocellular rays in J. deca does not support its
inclusion in Paraphyllanthoxylon (Wheeler & Lehman 2009; InsideWood 2010),
instead these characters bring it closer to Javelinoxylon. Several other Malvalean fossil
woods have been described (e.g., Müller-Stoll & Müller-Stoll 1949; Beauchamp et al.
1973; Privé-Gill & Pelletier 1981; Crawley 2001; Wheeler & Lehman 2000), but none
of these records have the combination of characteristics present in J. deca. The position
of Javelinoxylon within Malvaceae s.l., which includes Malvaceae, Bombacaceae,
Sterculiaceae and Tiliaceae (sensu APG III 2009) is uncertain. However, Wheeler et al.
(1994) suggested it is anatomically closer to Sterculiaceae (Sterculioideae) and
Tiliaceae (Grewioideae and Tilioideae, Bayer et al. 1999) than to Bombacaceae and
Malvaceae (Bombacoideae and Malvoideae respectively [Bayer et al. 1999]). At
present two species of Javelinoxylon have been described: J. multiporosum from the
Javelina Formation of the Big Bend National Park, Texas (Wheeler et al. 1994) and J.
weberi from the Olmos Formation in northern Mexico (Estrada-Ruiz et al. 2007). In
addition, two other xylotypes assigned to Javelinoxylon were described from the Olmos
Formation (Estrada-Ruiz et al. 2010). In the last two cases, the authors did not erect
new species because there was considerable anatomical variation in samples from the
Olmos Formation (also observed in Javelinoxylon samples from the Big Bend;
527
Estrada-Ruiz & Martínez-Cabrera — Javelinoxylon from Mexico
E.A. Wheeler, personal comm.) and because the small sample size of each of the Olmos
Formation Javelinoxylon xylotypes precluded analysis to determine whether there were
significant diferences between the samples. Most of the differences between the formally
erected Javelinoxylon species, the aforementioned Javelinoxylon xylotypes, and J. deca
are in quantitative characters, especially in the environmentally plastic vessel characters.
The other anatomical characters of J. deca fall within the range of the other
species/xylotypes of Javelinoxylon, but we believe they differ enough to justify a new
species. For example, J. deca differs from J. multiporosum (Wheeler et al. 1994) and
Javelinoxylon xylotype 2 (Estrada-Ruiz et al. 2010) in the height and width of multiseriate
rays. Javelinoxylon deca has vessel clusters, high (up to 1.1 mm) multiseriate rays and
septate and non-septate fibers, unlike J. weberi (Estrada-Ruiz et al. 2007), which has
exclusively septate fibers and shorter rays. Vessel-ray parenchyma pits in J. deca are of a
single type (rounded), a feature only shared with the Olmos Formation Javelinoxylon
xylotype 2. In the other species vessel-ray parenchyma pits are of two types. We believe
that the combination of vessel clusters, enlarged vessel-ray parenchyma pits that are round
and with reduced borders, occurrence of both septate and non-septate fibersand higher (up
to 1176 µ m) and wider (up to 100 µ m) rays justify erecting a new Javelinoxylon species,
J. deca. The other two records of Cretaceous woods with storied structure, one also in
Malvaceae s.l. and the other in Ebenaceae, are significantly different from J. deca.
Wheeleroxylon atascosense (Estrada-Ruiz et al. 2010), from the Olmos Formation, has
exclusively non-septate fibers,homocellular and low rays, and vessel-ray parenchyma pits
of two sizes. Ebenoxylon deccanensis (Trivedi & Srivastava 1982) has banded axial
parenchyma and mainly solitary vessels.
Common floristic elements in the Late Cretaceous along the Western Interior of
North America Javelinoxylon deca extends the geographic distribution of this genus
further west. It also extends the temporal span of this genus. As has been pointed out
before (Wheeler et al. 1994; Wheeler & Lehman 2005, 2009; Estrada-Ruiz et al. 2007,
2010), it seems the southern portion of the Western Interior of North America, southern
North America and northern Mexico, had floristic elements in common along the
margin of the Epicontinental Sea. Specificall, the genera Metcalfeoxylon, Javelinoxylon
and Paraphyllanthoxylon are shared between the San Juan Basin, New Mexico, and Big
Bend National Park, Texas, and the Sabinas Basin, Coahuila in northern Mexico, all of
which are younger than the San Carlos Formation. These floras, including those in the
San Juan Basin, such as those in the Kirtland and Fruitland formations, and the Olmos
Formation in the Sabinas Basin, which occupy deltaic plain positions in the Western
Interior, and those in the Aguja (a coastal lowland deposits) and Javelina (an inland
fluvialflood-plaindeposits) formations were part of a very large fluvialsystem (Wheeler
& Lehman 2005, 2009; Estrada-Ruiz et al. 2010). Apparently these forma- tions are
similar in floristic composition, while other formations of the same age in North
American, such as Panoche (California) and McNairy (Illinois) formations differ from
them and from each other (Page 1970, 1979; Wheeler et al. 1987).
IAWA Journal, Vol. 32 (4), 2011528
Incidence of storied structure in the Cretaceous of Northern Mexico Storied structure
is generally considered highly specialized (Bailey 1924) and is uncommon in fossil woods
from the Late Cretaceous (Wheeler & Baas 1991). Clearly, in northern Mexico during the
Late Cretaceous the incidence of this feature was high; at least 5 species with storied
structure have been described for Mexican Cretaceous communities. The incidence of
storied structure is more common in the Tertiary and increases through the Pliocene
(Wheeler & Baas 1993). Bailey (1923) suggested that storied structure is more prevalent
in species with short fusiform cambial initials and tends to occur in more derived
angiosperms. Other authors (e.g., Carlquist 2001) believe that there is no clear quantitative
evidence for this phyletic trend and that the claim storied structure is derived is highly
speculative. This work is an initial description of the Late Cretaceous Chihuahuan flora
and therefore it may be premature to speculate about possible foristic links between the
San Carlos Formation and the other florasfrom other geological formations of the Western
Interior of North America. However, apparently Javelinoxylon was a common plant in
lower latitudes of the Western Interior during the Late Cretaceous (Estrada-Ruiz et al.
2007; Wheeler & Lehman 2009).
ACKNOWLEDGMENTS We would like to acknowledge
D.E.C.A. Parque Cretácico A.C., especially Ing. Ernesto Carrillo and José Antonio Derma for
supporting the visit of EER to Chihuahua; Dr. Jesús Alvarado (Institute of Geology, UNAM) and his
students for their help collecting the fossil material (supported by UNAM throughout the project
PAPIIT IN225008), and INAH Mexico for providing administrative help. We also thank Ing.
Fernando Meléndez (Museo Semilla Centro de Ciencia y Tecnología, Chihuahua) for supporting the
visit of EER to Chihuahua. Rubén Cruz Vásquez and Dr. Celestina González-Arreola provided
information on the geology and age of the study area. Comments by Dori Thompson, Department of
Biology, Texas State University improved a preliminary English version. The authors thank Drs.
Jakub Sakala (Charles University, Czech Republic) and Lisa Boucher (University of Nebraska,
USA) for useful comments on this manuscript. This study is based in part on the Posdoctoral Project
of EER (Estancias Posdoctorales y Sabáticas al Extranjero para la Consolidación de Grupos de
Investigación) at the Department of Biology, Texas State University, Texas, USA (CONACyT
(137526)). The scholarship provided by CONACyT to HIMC is also appreciated.
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