A SYSTEMATIC REVISION OF THE LATE FURONGIAN TRILOBITES
FROM CERRO PELADO, MENDOZA, ARGENTINA
REVISIÓN SISTEMÁTICA DE LOS TRILOBITES DEL FURONGIANO TARDÍO
DE CERRO PELADO, MENDOZA, ARGENTINA
M. FRANCO TORTELLO
División Paleozoología Invertebrados, Museo de Ciencias Naturales, Paseo del Bosque
s/ n, 1900 La Plata, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
tortello@fcnym.unlp.edu.ar
41 páginas y 6 figuras.
Propuesta para el cabezal: TORTELLO: FURONGIAN TRILOBITES FROM
MENDOZA, ARGENTINA
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Abstract. Late Furongian (late Cambrian) trilobites are described from the black, deep
water limestones of the El Relincho Formation in Cerro Pelado, Precordillera of
Mendoza, western Argentina. In addition, selected type specimens of the Carlos
Rusconi collections at the Museo de Ciencias Naturales y Antropológicas J.C. Moyano,
(Mendoza) are revised. The assemblages are largely dominated by the agnostoid
Lotagnostus peladensis (Rusconi), which proved to be a species with variably effaced
dorsal furrows. Polymeroids include Mendoparabolina pirquinensis Rusconi, Hungaia
peladensis Rusconi, and Loganellus cf. macropleurus Rasetti, as well as some
fragmentary remains of uncertain affinities. Generic occurrences strongly support
connections with Laurentia. Although the species identified are endemic to the southern
Precordillera, they mostly resemble faunas from the lower Saukia Zone of western
North America, and the Onchonotus richardsoni and Keithia subclavata faunas of
eastern Canada and USA.
Key words. Trilobites. Furongian. Cerro Pelado. Mendoza. Argentina.
Resumen. REVISIÓN SISTEMÁTICA DE LOS TRILOBITES DEL FURONGIANO
TARDÍO DE CERRO PELADO, MENDOZA, ARGENTINA. Se describen trilobites
del Furongiano tardío (Cámbrico tardío) de las calizas oscuras de la Formación El
Relincho en la localidad de Cerro Pelado, Precordillera de Mendoza, Argentina.
Asimismo, se revisan especímenes tipo de las colecciones Carlos Rusconi del Museo de
Ciencias Naturales y Antropológicas J.C. Moyano (Mendoza). Las asociaciones están
dominadas por el agnóstido Lotagnostus peladensis (Rusconi), el cual presenta surcos
dorsales con un grado de expresión muy variable. Los poliméridos incluyen a
Mendoparabolina pirquinensis Rusconi, Hungaia peladensis Rusconi, Loganellus cf.
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macropleurus Rasetti, y algunos restos fragmentarios de afinidades inciertas. Los
géneros registrados indican fuertes afinidades con Laurentia. Aunque las especies
identificadas son endémicas de la Precordillera, ellas muestran mayores similitudes con
trilobites de la parte inferior de la Zona de Saukia del oeste de Norteamérica, y de las
faunas de Onchonotus richardsoni y Keithia subclavata del este de Canadá y Estados
Unidos.
Palabras clave. Trilobites. Furongiano. Cerro Pelado. Mendoza. Argentina.
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THE Cambrian System is well represented in the southern Precordillera of Mendoza,
western Argentina. The lower Paleozoic of this region is mainly characterized by the
occurrence of isolated middle and upper Cambrian carbonate blocks chaotically mixed
within Middle to Upper Ordovician siliciclastic sequences (Bordonaro, 1992, 2003a,b
and references therein; Keller, 1999; Heredia and Beresi, 2004). Many olistoliths
represent deep water facies containing shelly faunas such as trilobites, brachiopods,
hyoliths, mollusks and echinoderms.
The Cerro El Solitario, El Totoral, and the San Isidro area are the most typical
fossiliferous sites in Mendoza; in addition, a carbonate platform to upper slope
succession is exposed in Cerro Pelado to the northwest of Mendoza city (Fig. 1). This
platform represents represents the only autochthonous Cambrian sequence in the
southern Precordillera, and is composed of grey limestones of the Cerro Pelado
Formation and fossiliferous black limestones and shales of the El Relincho Formation
(Heredia, 1990; Bordonaro and Banchig, 1996; Keller, 1999). Rusconi (1951a,b, 1953a)
briefly described several new species of agnostoids (Homagnostus peladensis, H.?
manantialensis, Triplagnostus pedrensis, T. planus, Goniagnostus rotundatus, G.
verrucosus, Phalacroma lasherensis, Spinagnostus pedrensis) and polymeroid trilobites
(Parabolina? australis, Mendoparabolina pirquinensis, Prosaukia peladensis, Orria
peladensis, Levinia manantialensis, Briscoia peladense, Hungaia peladense,
Dalmanitina? peladense) from Cerro Pelado, which was originally referred to the upper
Cambrian (Rusconi, 1955a, 1956, 1962). Subsequently, Borrello (1965, 1971) collected
numerous additional specimens from this locality and, after a preliminary examination,
first cited the occurrence of Lotagnostus Whitehouse, 1936 and Bienvillia Clark, 1924,
assigning the succession to the Saukia Zone of the standard North American trilobite
zonation. More recently, Shergold et al. (1995) redescribed Lotagnostus peladensis
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(Rusconi) and Neoagnostus sp., whereas Tortello and Bordonaro (1997) reillustrated the
type specimens of Rusconi's agnostoid species.
The purpose of the present paper is to describe for the first time the trilobites from
Cerro Pelado of the Ángel V. Borrello collections in the Museo de La Plata, Argentina
(Borrello, 1971). The assemblages examined are largely dominated by well-preserved
specimens of Lotagnostus, a biostratigraphically important genus whose interspecific
and intraspecific variability is currently under discussion (e.g., Westrop, 1995; Peng and
Babcock, 2005; Rushton, 2009; Westrop et al., 2011). In addition, most of the
associated polymeroids are assignable to those erected by Rusconi (1951a,b, 1953a),
which have not been fully revised since the early 1950s. Species of Mendoparabolina
Rusconi, 1951a, Hungaia Walcott, 1914 and Loganellus Devine, 1863 are redescribed
herein, and their paleobiogeographic and biostratigraphic implications are updated.
STRATIGRAPHIC SETTING, AGE AND PALEOBIOGEOGRAPHIC
REMARKS
The El Relincho Formation (Heredia, 1990, 1996) is a 350 m - thick upwarddeepening succession of deep water micritic limestones (mudstones and wackstones)
and alternating black shales exposed at Cerro Pelado, about 45 km WNW of Mendoza
city and ~3000 m on sea level (Keidel, 1939; Rusconi, 1951a, 1956; Varela, 1973;
Heredia, 1990, 1996; Keller, 1999) (Fig. 1). Columnar sections of the unit were
provided by Heredia (1996, fig. 2; 1999, fig. 1) and Keller (1999, fig. 47).
Dark grey and black limestones of the lowermost part of the El Relincho
Formation contain shelly fossils (trilobites, brachiopods, hyoliths, echinoderms) which
were discovered by C. Rusconi and M. Tellechea (Museo de Historia Natural de
Mendoza) in the early 1950s. As stated above, Rusconi (1955a, 1956, 1962) originally
referred the trilobites to the upper Cambrian (“Horizonte Peladense” of Rusconi,
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1955a), whereas Borrello (1971) reassigned them to the Saukia Zone on the basis of the
occurrences of Lotagnostus and Bienvillia. More recently, crucial biostratigraphic
information was provided by Heredia (1990, 1996, 1999) and Heredia and Hünicken
(1995), who described conodonts of the late Furongian Proconodontus tenuiserratus
Zone and the Eoconodontus notchpeakensis Subzone (Eoconodontus Zone) from the
lower part of the formation (see also Miller et al., 2011).
Bordonaro (1985) and Shergold et al. (1995) pointed out the occurrence of the
Furongian genus Lotagnostus in the Precordillera of Mendoza. In addition, Shergold et
al. (1995, p. 246) noted that Mendoparabolina pirquinensis Rusconi, 1951a, which in
Cerro Pelado and the San Isidro area is associated with Lotagnostus peladensis
(Rusconi), is similar to Bienvillia corax (Billings, 1865) from eastern North America,
suggesting a possible correlation with the Keithia schucherti Fauna of western
Newfoundland and the upper Saukia Zone of continental USA (e.g., Oklahoma, Central
Texas, Utah) (see also Bordonaro, 1992, 1993, 2003a,b; Bordonaro et al., 1999; Jell and
Adrain, 2003).
[Figure 1]
As originally indicated by Rusconi (1951b, p. 9) and Borrello (1971), most of the
trilobite species from Cerro Pelado are restricted to the southern Precordillera and can
be assigned with confidence to the late Furongian (= late Sunwaptan). Lotagnostus
peladensis proved to be a highly variable species (see below), which strongly resembles
both Lotagnostus sp. indet., from the Naustia papilio Fauna of northwest Canada
(Westrop, 1995; Westrop et al., 2011, fig. 11.A–I), and Lotagnostus obscurus Palmer,
1955 sensu Westrop et al. (2011), from the lower Saukia Zone of the Eureka District,
Nevada, USA (Palmer, 1955; Westrop et al., 2011, fig. 7.A–I). The material from
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northwest Canada correlates into the upper Illaenurus Zone of Alberta and the
Prosaukia pyrene Subzone of western USA (Landing et al., 2011).
Although all the polymeroid species described below are endemic, their
systematic affinities have valuable biostratigraphic and paleobiogeographic
implications. These trilobites are mainly comparable to those of the Onchonotus
richardsoni and Keithia subclavata faunas of eastern Laurentia. As stated below,
Hungaia peladensis Rusconi, 1953a shows major similarities with the type species H.
magnifica (Billings, 1860), from the Keithia subclavata Fauna of eastern North America
(western Newfoundland, Quebec and Maryland; e.g., Rasetti, 1944, 1959; Ludvigsen et
al., 1989), whereas Loganellus cf. macropleurus resembles mainly L. macropleurus
Rasetti, 1944, from the Onchonotus richardsoni Fauna of western Newfoundland and
Quebec (Rasetti, 1944, 1945; Ludvigsen et al., 1989), and L. belli (Billings, 1860), from
the Keithia subclavata Fauna of Quebec and Vermont (e.g., Rasetti, 1944; Ludvigsen et
al., 1989, pl. 5, figs. 16, 17).
SYSTEMATIC PALEONTOLOGY
The material studied consists of more than 400 specimens from the Ángel V.
Borrello collections in the Museo de La Plata (MLP), Argentina. In addition, selected
type specimens of the Carlos Rusconi collections at the Museo de Ciencias Naturales y
Antropológicas “Juan Cornelio Moyano” (MCNAM), Mendoza, Argentina, are
illustrated in Fig. 6. All specimens were whitened with magnesium oxide vapors before
photographing. The morphological terms used below have been mostly defined by
Shergold et al. (1990) and Whittington and Kelly (1997).
Abbreviations. sag, sagittally; exsag, exsagittally; long, longitudinally; tr,
transversally.
Order AGNOSTIDA Salter, 1864a
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Family AGNOSTIDAE M’Coy, 1849
Subfamily AGNOSTINAE M’Coy, 1849
Genus Lotagnostus Whitehouse, 1936
Type species. Agnostus trisectus Salter, 1864b; original designation. Upper Furongian
of England.
Discussion. Lotagnostus is a geographically widespread Furongian genus which is
characterized by having a variably effaced exoskeleton with a long (sag.) anteroglabella,
a straight to backwardly bent transglabellar furrow (F3), a distinct F2 furrow,
proportionately large basal lobes, a long (sag.) pygidial axis, trilobate pygidial M1 and
M2 lobes, a semiovate to ogival posteroaxis with a gently inflated intranotular axis, and
a well developed terminal node (e.g., Palmer, 1955; Öpik, 1963; Shergold, 1975; Lu and
Lin, 1980, 1984; Shergold et al., 1990; Peng, 1992; Shergold and Laurie, 1997).
Recently, Westrop (1995) and Westrop et al. (2011) considered the partially effaced
taxon Distagnostus Shergold, 1972 to be a junior synonym of Lotagnostus.
Westrop et al. (2011) pointed out the need to review many Lotagnostus species on
the basis of well preserved, large samples, in order to appropriately assess their
intraspecific variability. Peng and Babcock (2005) regarded L. americanus (Billings,
1860) as a variably scrobiculate taxon of great biostratigraphic value within the
Furongian Series, and proposed an extensive synonymy list [including L. trisectus
(Salter, 1864b), L. asiaticus Troedsson, 1937, L. punctatus Lu, 1964, L. obscurus
Palmer, 1955, L. xinjiangensis Zhang, 1981, among others] for it. However, I concur
with Rushton (2009) and Westrop et al. (2011) in regarding L. americanus and L.
trisectus as separate, valid species. Similarly, L. obscurus is more appropriately treated
as a valid, non-scrobiculate species of Lotagnostus (Westrop et al., 2011).
Lotagnostus peladensis (Rusconi, 1951a)
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Figures 2.1–28, 3.1–7
1951a. Homagnostus peladensis Rusconi, p. 2, fig. 1.
1951b. Phalacroma lasherensis Rusconi, p. 8, fig. 10.
1995. Lotagnostus (Lotagnostus) peladensis (Rusconi), Shergold, Bordonaro and Liñán,
p. 244–246, pl. 1, figs. 1–9 (see for further synonymy).
1995. Lotagnostus (Lotagnostus) peladensis (Rusconi), Bordonaro and Banchig, pl. 1,
figs. 15, 16.
1997. Lotagnostus (Lotagnostus) lasherensis (Rusconi), Tortello and Bordonaro, p. 75,
76, fig. 3.5.
Emended diagnosis. A species of Lotagnostus with dorsal furrows effaced to varying
degrees (exfoliated specimens en grande tenue; testate specimens slightly to almost
completely effaced); genae smooth to very faintly scrobiculate; basal lobes
proportionately short (exsag.), extending forward to point just behind level of axial
glabellar node; pygidial acrolobe unconstricted, non-scrobiculate; pygidial anteroaxis
with a conspicuous central ridge extending along M1 and M2; F1 furrows not connected
across the axis; posteroaxis long, ogival, with trisection imperceptible or very poorly
defined.
Material. One hundred and fifty-five cephala and 121 pygidia [MLP 24219(1–7, 9–12),
24233(2–8, 10–13), 24234(1, 4, 6, 7), 24235(1–3), 24352(1–4, 7, 9–13), 24353(3–8,
10), 24410(2, 4), 34460–34462, 34464, 34466, 34469–34471, 34488, 34489].
Geographic and stratigraphic provenance. Upper Furongian. El Relincho Formation,
Cerro Pelado locality, Mendoza, Argentina.
Discussion. Based on material from both Cerro Pelado and the San Isidro area,
Mendoza, Shergold et al. (1995, p. 246) redescribed Lotagnostus peladensis (Rusconi,
1951a) and suppressed Homagnostus manantialensis Rusconi (1951a, p. 2, fig. 2;
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Tortello and Bordonaro, 1997, fig. 3.2) and Triplagnostus pedrensis Rusconi (1951b, p.
7, fig. 7; Tortello and Bordonaro, 1997, fig. 3.3) as subjective junior synonyms. The
examination of additional specimens from the Borrello collections contributes to
improving the diagnosis and synonymy of L. peladensis. Although most of the
specimens studied have smooth genae, some well preserved moulds exhibit very faint
indications of scrobicules close to the marginal furrow (Fig. 2.5). The axial glabellar
node is generally slightly elongate (sag.), but in some cases it is represented by a
smaller, subcircular knob (e.g., Fig. 2.2, 2.12; see also Shergold et al., 1995, pl. 1, fig.
2).
[Figure 2]
In addition, it is important to note that Lotagnostus peladensis shows a high
variation in the degree of expression of the cephalic dorsal furrows. This species
includes exfoliated sclerites with their dorsal furrows distinct (e.g., Fig. 2.1, 2.3;
Shergold et al., 1995, pl. 1, figs. 1–4), as well as testate specimens partly (e.g., Fig.
2.16) or almost completely effaced (Fig. 2.12, 2.17). The latter represent late holaspides
showing complete effacement of the anterior half of the glabella and the posterior part
of the median preglabellar furrow. Additionally, the material studied shows evidence of
distortion, which affected the original convexity and the cephalic and pygidial outline
(e.g., compare Figs. 2.23 and 2.26). Sagittally compressed cephala (Fig. 2.14) have
proportionately broader and more rounded outlines than non-flattened specimens (Fig.
2.1, 2.16).
Phalacroma lasherense Rusconi (1951b, p. 8, fig. 10; see Tortello and Bordonaro,
1997, fig. 3.5) was erected on the basis of a single, partially effaced cephalon from
Cerro Pelado that is comparable with the material described above. Thus, it is regarded
here as a subjective junior synonym of Lotagnostus peladensis.
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A high variability in the expression of dorsal furrows was also recorded in
Lotagnostus “sp. indet.”, from the Naustia papilio Fauna of the Rabbitkettle Formation,
northern Mackenzie Mountains, northwest Canada (Westrop, 1995, pl. 1, figs. 17–20;
Westrop et al., 2011, fig. 11.A–I), as well as in Lotagnostus obscurus Palmer, 1955
sensu Westrop et al. (2011), from the Windfall Formation of the Eureka District,
Nevada, USA (Palmer, 1955, pl. 19, figs. 5–7, 10; Westrop et al., 2011, fig. 7.A–I).
These relatively effaced taxa from western and northwestern North America were
described on scarce specimens showing a strong convexity of cephala and pygidia, a
non-scrobiculate cephalon, short basal lobes, a weakly trisected pygidial posteroaxis,
and unconstricted acrolobes. They may represent a single species, although this cannot
be demonstrated with the available samples (Westrop et al., 2011, p. 592). Lotagnostus
peladensis, as revised herein, is clearly similar to both L. obscurus and L. “sp. indet.”.
Lotagnostus peladensis seems to differ only by having less convex sclerites and a better
defined pygidial axial node, which may lack specific significance.
Lotagnostus sp., from the late Sunwaptan Keithia schucherti Fauna of western
Newfoundland and Vermont (Ludvigsen et al., 1989, pl. 1, figs. 1–8, 12–14-only-; see
Westrop et al., 2011, p. 584, 586), resembles L. peladensis by lacking both scrobicules
on the genae, and an intranotular axis on the posterior lobe of the pygidium. However,
the pygidium of the former is differentiated by having a much longer (sag.) axis, and F1
furrows that are connected across the axis. Lotagnostus hedini (Troedsson), from the
uppermost Furongian of China (L. hedini Zone), Kazakhstan (Euloma limitarisTaoyuania Zone) and western Newfoundland (Phylacterus saylesi Fauna) possesses, in
addition, a constricted pygidial acrolobe (e.g., Troedsson, 1937, pl. 1, figs. 6–8; Lu and
Lin, 1980, pl. 1, figs. 8, 9; 1984, pl. 3, figs. 12, 13; Apollonov et al., 1984, pl. 14, figs.
1–8; Ludvigsen et al., 1989, pl. 1, figs. 9–11-only-; Westrop et al., 2011, p. 584).
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Lotagnostus americanus (Billings, year), as recently reviewed by Rushton (2009)
and Westrop et al. (2011), is restricted to boulders of the Levis Formation, Quebec, that
are correlative with the late Sunwaptan Keithia subclavata Fauna of western
Newfoundland (Billings, 1860, fig. 1a,b; Rasetti, 1944, pl. 36, figs. 1, 2; Ludvigsen et
al., 1989, pl. 1, figs. 15, 16-only-; Peng and Babcock, 2005, fig. 2.2–2.4-only-; Rushton,
2009, fig. 1.J–O). As L. peladensis, it shows a poorly defined trisection of the pygidial
posteroaxis that may be absent in small specimens (Westrop et al., 2011). However, the
Canadian species differs in having weak but distinct cephalic scrobicules, and a gently
constricted pygidial acrolobe.
As stated by Shergold et al. (1995), Lotagnostus peladensis differs from
Lotagnostus atenuatus (Rusconi), from the Furongian of the San Isidro area, Mendoza
(Rusconi, 1955b,c, pl. 2, figs. 13, 14; Shergold et al., 1995, pl. 1, figs. 10, 11; Tortello
and Bordonaro, 1997, fig. 3.4), because the latter is more scrobiculate, and has a
semiovate posterior pygidial lobe with a well defined trisection. Lotagnostus shergoldi
Tortello in Esteban and Tortello (2007, fig. 8.A–I, L), from the uppermost Furongian
(Parabolina frequens argentina Zone) of the Cordillera Oriental, northwestern
Argentina, is distinguished by lacking both a conspicuous pygidial ridge along M1 and
M2, and posterolateral spines.
Lotagnostus cf. trisectus (Salter), from the upper Furongian (middle Peltura
scarabaeoides Zone) of Nova Scotia, Avalonian Canada (Westrop et al., 2011, figs.
2.A–N, 3.A–G), differs from L. peladensis in having apparent scrobicules on the genae,
a more posteriorly located median glabellar node, and a pygidial posteroaxis with
perceptible notular furrows, which diverge anteriorly. Both L. peladensis and L.
germanus (Matthew, 1901) from Nova Scotia (Westrop et al., 2011, fig. 4.A–O) have
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an ill-defined trisection of the posteroaxis, but the latter species is distinguished by
showing a scrobiculate cephalon and larger posterolateral pygidial spines.
The type species Lotagnostus trisectus (Salter, 1864b), from the Peltura minor
Zone and the lower part of the P. scarabaeoides Zone of Avalonia and coeval beds of
Sweden, Siberia, Kazakhstan, China, Australia (Tasmania), eastern North America, and
the Argentinian Precordillera (Peng and Babcock, 2005, fig. 2.5–2.27, and references
therein; Rushton, 2009, figs. 1.A–I, P, 2.A–L, and references therein), further differs
from L. peladensis because the former possesses strong scrobicules on the genae, longer
(exsag.) basal lobes, and a pronounced longitudinal trisection of the posterior lobe of the
pygidium.
[Figure 3]
Family DIPLAGNOSTIDAE Whitehouse, 1936 emend. Öpik, 1967
Subfamily PSEUDAGNOSTINAE Whitehouse, 1936
Genus Pseudorhaptagnostus Lermontova, 1951
Remarks. After revising the Pseudorhaptagnostus simplex Lermontova, 1951 type
material, Nielsen (1997) regarded Pseudorhaptagnostus as a valid senior synonym of
Neoagnostus Kobayashi, 1955; concept that is followed here.
Subgenus Pseudorhaptagnostus Lermontova, 1951
Type species. Pseudorhaptagnostus simplex Lermontova, 1951; original designation.
Upper Furongian of Kazakhstan.
Pseudorhaptagnostus (Pseudorhaptagnostus) sp.
Figure 4.1–4
Material. Two cephala and 9 pygidia [MLP 24233(6), 24235(1), 24352(1, 12),
24353(4), 24410(2, 4), 34467, 34473, 34489].
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Geographic and stratigraphic provenance. Upper Furongian. El Relincho Formation,
Cerro Pelado locality, Mendoza, Argentina.
Discussion. This rare, tiny agnostoid is recorded in association with Lotagnostus
peladensis. It exhibits a long, subparallel sided glabella; a faint, forward- and outwardcurving F3 furrow; an elongate axial glabellar node; a shallow but distinct preglabellar
furrow; non-scrobiculate acrolobes; a tri-lobed anteroaxis carrying a prominent axial
pygidial node; and effaced accessory furrows. The overall appearance of these
specimens, and particularly the incorporation of the third pygidial segment into the
anteroaxis, indicates affiliation with the cosmopolitan subgenus Pseudorhaptagnostus
(Pseudorhaptagnostus) Lermontova, 1951 (e.g., Shaw, 1951; Shergold, 1977; Shergold
et al., 1990; Nielsen, 1997). Although imperfect preservation prevents a species
assignment, they can be confidently assigned to the “Bilobus group” of Shergold
(1977), which is typically represented by Pseudorhaptagnostus bilobus (Shaw, 1951, pl.
24, figs. 17–22; Shergold, 1977, fig. 16.7–8; Shergold et al., 1990, fig. 16.1b, c).
Rusconi (1951b) and Shergold et al. (1995) reported scarce material of
Pseudagnostinae from Cerro Pelado. Rusconi (1951b, fig. 9) described two pygidia of
the new species “Spinagnostus” pedrensis (regarded as an “unassigned pseudagnostid
species” by Shergold, 1977; see also Tortello and Bordonaro, 1997, p. 80, fig. 4.14),
which are comparable with the specimens studied herein. However, the former differ by
having a smaller axial node. In addition, Shergold et al. (1995, pl. 2, fig. 15) described
one small pygidium of Pseudorhaptagnostus (Pseudorhaptagnostus) sp. that is
distinguished by its proportionately wider (tr.; sag.) border.
Order OLENIDA Adrain, 2011
Family OLENIDAE Burmeister, 1843
Subfamily TRIARTHRINAE Ulrich, 1930
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Genus Mendoparabolina Rusconi, 1951a
Type species. Mendoparabolina pirquinensis Rusconi, 1951a; original designation. Late
Furongian of Cerro Pelado, Mendoza, Argentina.
Emmended diagnosis. An olenid genus with a subquadrate glabella; lateral glabellar
furrows distinct and backwardly directed; preglabellar field short (sag.), flat to concave;
palpebral ridges distinct, oblique; librigenae caecate; pygidium bilobate, with a
subparallel sided axis (emended from Rusconi, 1951a, p. 3).
Discussion. Shergold et al. (1995, p. 246) suggested that Mendoparabolina pirquinensis
could be regarded as a species of Bienvillia Clark, 1924 very close to B. corax (Billings,
1865) (see also Jell and Adrain, 2003, p. 404; Cerdeño, 2005). However, the presence of
a short and non-inflated frontal area, a poorly-defined anterior cranidial furrow, and a
subparallel sided pygidial axis precludes assignment to Bienvillia as revised by
Ludvigsen and Tuffnell (1983). Mendoparabolina Rusconi is considered herein as an
available name, and a revised description of the type species M. pirquinensis is provided
below. According to the above diagnosis, Parabolina? naomi Pratt, 1992, from the
upper Furongian of northwest Canada, is also assignable to this genus.
Mendoparabolina pirquinensis Rusconi, 1951a
Figures 4.5–25; 6.1, 2, 12(left)
1951a. Mendoparabolina pirquinensis Rusconi, p. 3, fig. 4.a,b.
1954b. Mendoparabolina pirquinensis Rusconi, Rusconi, p. 103.
Type material. Cranidium MCNAM 9709, holotype [sketched by Rusconi (1951a, fig.
4.a); reillustrated in Fig. 6.1]; pygidium MCNAM 9712, paratype [sketched by Rusconi
(1951a, fig. 4.b); reillustrated in Fig. 6.2].
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Additional material. Sixty seven cranidia and 45 pygidia [MLP 24219(1, 2, 5, 7–9, 12,
13), 24233(3, 4, 8–10, 13), 24234(2, 4, 5, 8, 9), 24235(1, 3), 24352(2–4, 6–8, 11, 13),
24353(1, 3, 5, 9, 10), 34461, 34463, 34465, 34472, 34474–34487].
Geographic and stratigraphic provenance. Upper Furongian. El Relincho Formation,
Cerro Pelado locality, Mendoza, Argentina.
[Figure 4]
Description. Cranidium subtrapezoidal, slightly convex, with forwardly curved anterior
margin and downsloping fixed cheeks. Glabella large, moderately elevated above genal
region, slightly longer (sag.) than wide (tr.), somewhat tapered, with truncate or slightly
indented anterior margin, surrounded by well-defined axial furrows; occupies about 85–
90% of the total cranidial length and a half of maximum width of the cranidium; three
pairs of backwardly oblique lateral furrows present at sides of glabella; S1 firmly
impressed, sinuous, disconnected at middle in most of the specimens and transglabellar
in others; S2 as conspicuous as S1, straight to slightly bowed forward; S3 shallower
than S1 and S2; some cranidia show indications of a forwardly oblique S4 furrow,
which is very close to S3 and connects to the axial furrow; occipital ring with rounded
posterior margin and a distinct median node; occipital furrow bowed forward medially
and straight, oblique forward laterally. Preglabellar field short (sag.), flat to concave;
anterior border shorter (sag.) than preglabellar field, little upturned, delimited by a
shallow border furrow; anterior facial suture moderately divergent; eye ridge distinct,
oblique, running from axial furrow at level of S3; palpebral area of the fixigena narrow
(tr.), about 0.3 width of adjacent glabella; palpebral lobe small, elevated above fixigena,
forward of glabellar midpoint, surrounded by a very faint palpebral furrow; posterior
facial suture oblique; posterior fixigena wide (tr.) and triangular in outline; posterior
border transverse and well defined by a shallow posterior border furrow. Largest
16
observed cranidium 13 mm in length. Fragmentary librigenae show a densely caecate
dorsal surface (Fig. 4.8).
Pygidium bilobate because of posterior medial indentation; width approximately
twice length. Axis convex, elevated above pleural fields, anterior width more than one
third maximum width of pygidium, parallel sided to slightly tapered backward, with a
truncate or slightly indented posterior margin, occupying about 75–80% of the total
pygidial length; it is composed of a short (sag.) articulating half ring, three axial rings,
and a rectangular terminal piece. Pleural field slightly convex, crossed by four sets of
well defined, oblique pleural furrows, delicate interpleural lines, and a postaxial median
ridge; distal parts of pleural furrows strongly curving backward; border furrow
indistinct; pygidial border narrow, depressed, without marginal spines.
Discussion. The cephalon of Mendoparabolina pirquinensis is difficult to distinguish
from that of M. naomi (Pratt), from the upper Furongian (Rabbitkettle Formation,
Proceratopyge rectispinata Zone) of the southern Mackenzie Mountains, northwest
Canada (Pratt, 1992, pl. 10, figs. 1–8, text-fig. 29), because both share a subquadrate
glabella, a similar pattern of glabellar furrows, a short, flat to concave preglabellar field,
oblique palpebral ridges, and caecate librigenae. The Canadian species is differentiated
only by possessing a pygidium with a posteriorly rounded axis, and one pair of short
border spines.
As stated by Shergold et al. (1995), Mendoparabolina pirquinensis is
comparable with Bienvillia corax (Billings, 1865), a species from the Furongian of
Quebec (Levis Formation), Vermont (Gorge Formation) and western Newfoundland
(Shallow Bay Formation, Keithia schucherti Fauna) (Billings, 1865, fig. 322a; Rasetti,
1944, pl. 36, figs. 51, 52; Rasetti, 1954, pl. 61, fig. 15; Fortey et al., 1982, pl. 2, fig. 23;
Ludvigsen et al., 1989, pl. 4, figs. 18–22) that is partially known by its cranidium.
17
However, the latter is distinguished from M. pirquinensis by its sub-circular glabella, its
non-sinuous S1 glabellar furrow, and its inflated preglabellar field. Bienvillia cf. corax,
from the Furongian (Shallow Bay Formation; Onchonotus richardsoni and Keithia
subclavata faunas) of western Newfoundland (Ludvigsen et al., 1989, pl. 4, figs. 23–
26), is more similar to M. pirquinensis because of its barrel-shape glabella, but it differs
from the Argentinian species by having a convex and longer frontal area, as well as a
slightly curved S1 glabellar furrow.
Bienvillia? australis (Rusconi, 1951a, p. 3, fig. 3.a–c; Castellaro, 1963, p. 34, 35)
(Fig. 6.3, 6.4), from the Furongian of Cerro Pelado, is distinguished mainly by having a
convex preglabellar field and a tapered pygidial axis. Bienvillia terranovica Rasetti,
from the Lower Ordovician of Newfoundland (Rasetti, 1954, pl. 61, figs. 7–12), further
differs in possessing very faint lateral glabellar furrows and eye ridges.
The olenid Plicatolinella ocula Robison and Pantoja-Alor, from the ?upper
Furongian of Oaxaca, Mexico (Robison and Pantoja-Alor, 1968, pl. 103, figs. 24–26, pl.
104, figs. 1–4), exhibits a pygidium that is identical to that of Mendoparabolina
pirquinensis, but the former species strongly differs by showing distinct, transverse
lateral glabellar furrows S3 and S4, and larger eye ridges and palpebral lobes.
Family IDAHOIIDAE Lochman, 1956
Remarks. Adrain (2011) noted that several families of the Order Olenida may be
subject to synonymy. Westrop (1995) regarded Loganellidae Rasetti in Moore, 1959 as
a junior synonym of Idahoiidae Lochman, 1956, pointing out that both share divergent
anterior sections of the facial suture, a trapezoidal or quadrate glabella, palpebral lobes
that are close to the glabella and behind cranidial midlength, and a relatively large, flat
pygidium with shallow pleural furrows, a weakly convex border and entire margins.
Genus Loganellus Devine, 1863
18
Type species. Olenus? logani Devine (1863, p. 95) by synonymy with Loganellus
quebecensis Devine (1863, p. 98) (erected in same paper and referring to same species).
Furongian of Quebec, Canada.
Loganellus cf. macropleurus Rasetti, 1944
Figure 5.1–6
Material. Two cranidia and three pygidia [MLP 24352(2), 24353(4a, b), 24410(1),
34468].
Geographic and stratigraphic provenance. Upper Furongian. El Relincho Formation,
Cerro Pelado locality, Mendoza, Argentina.
Description. Cranidium convex, with rounded anterior margin and downsloping fixed
cheeks; glabella very long, inflated, slightly tapered and broadly rounded anteriorly,
surrounded by well defined axial furrows; it occupies about 88% of the total length of
the cranidium; S1 furrow well defined, strongly oblique backward, slightly sinuous; S2
furrow shallower, shorter (tr.) and less oblique than S1 furrow, somewhat curved;
occipital ring slightly bowed backward, approximately 13% length (sag.) of glabella,
with rounded posterior margin and faint indications of a small median node; occipital
furrow slightly bowed backward, effaced both medially and near axial furrows; anterior
cranidial border weakly convex, short (sag.; exsag.), constant in length, clearly
delimited by a narrow border furrow; preglabellar field downsloping, sagittal length
about two times that of anterior border, with lateral margins somewhat divergent;
palpebral area of the fixigena about 0.3 width of adjacent glabella; palpebral lobe short
(exsag.), little elevated above fixigena, opposite S1 furrow; eye ridge faint, oblique,
reaching axial furrow in front of S2 furrow; posterior facial suture strongly divergent
backward, sigmoid; posterior fixigena subtriangular, wide (tr.), with a shallow border
furrow and a narrow (exsag.), convex posterior border.
19
Pygidium weakly convex, semielliptical in outline, transverse maximum width
more than twice sagittal length; axis long, conical, elevated above level of pleural fields,
evenly and moderately tapering backward, rounded at posterior end, surrounded by
narrow axial furrows; it is composed of a short (sag.) articulating half ring, five or six
axial rings, and a rounded terminal piece; pleural field weakly convex, crossed by three
or four barely perceptible pleural furrows; border furrow indistinct; border fairly
concave; posterior margin entire.
[Figure 5]
Discussion. The specimens studied represent an idahoiid with an anteriorly-rounded,
gently tapered glabella; distinct S1 and S2 furrows; a short (sag.), bandlike anterior
cranidial border; palpebral lobes that are opposite S1 furrow and some distance from
glabella; and a semielliptical pygidium with length less than half of width. Therefore,
they essentially agree with the diagnosis of Loganellus Devine, 1863 (Rasetti, 1944, p.
246; Ludvigsen and Westrop in Ludvigsen et al., 1989, p. 16).
Loganellus cf. macropleurus mostly resembles L. macropleurus Rasetti, 1944,
from the upper Furongian of Quebec (Levis Formation) and western Newfoundland
(Shallow Bay Formation; Onchonotus richardsoni Fauna) (Rasetti, 1944, pl. 38, figs.
15–17; Rasetti, 1945, pl. 61, figs. 12, 13; Ludvigsen et al., 1989, pl. 6, figs. 8–10), by
having a conical glabella and a similar pattern of glabellar lateral furrows. However, the
Argentinian material is distinguishable by its distinct preglabellar field, its less
divergent anterior facial suture, and its wider (tr.) palpebral area of the fixigena.
Loganellus cf. macropleurus and L. belli (Billings, 1860), from the upper
Furongian of Quebec (Levis Formation) and Vermont (Gorge Formation) (e.g., Rasetti,
1944, pl. 38, figs. 18–20; Ludvigsen et al., 1989, pl. 5, figs. 16, 17, and references
therein), share a moderately divergent anterior facial suture, a forwardly bowed anterior
20
cranidial margin, a gently tapering glabella, and a medially effaced occipital furrow, but
the latter exhibits a shorter (sag.) preglabellar field, as well as wider pleural furrows on
the pygidium.
Loganellus laeviusculus (Raymond, 1937), from the upper Furongian of Vermont
(Gorge Formation) and western Newfoundland (Shallow Bay Formation; Keithia
subclavata and Keithia schucherti faunas) (Raymond, 1937, pl. 1, figs. 10–13;
Ludvigsen et al., 1989, pl. 6, figs. 1–7), differs from L. cf. macropleurus because the
former lacks a preglabellar field, and possesses a glabella that is less rounded anteriorly.
The type species Loganellus logani (Devine, 1863), from the Furongian of Quebec
(Levis Formation), western Newfoundland (Shallow Bay Formation; Onchonotus
richardsoni and Keithia schucherti faunas), Maryland (Frederick Limestone), and
northwest Canada (Rabbitkettle Formation, Noelaspis bilobata Zone) (e.g., Rasetti,
1944, pl. 38, figs. 13, 14, 21–23; Ludvigsen et al., 1989, pl. 5, figs. 8–15, and references
therein; Westrop, 1995, pl. 8, figs. 1, 2), further differs in having a nearly transverse
anterior cranidial margin, sharply divergent anterior branches of facial suture, and a
glabella sub-cuadrangular in outline.
As stated by Ludvigsen et al. (1989), Loganellus? arcus Palmer, year from the
upper Furongian of Alaska (Palmer, 1968, pl. 13, figs. 6–8, 11), differs from all other
species of Loganellus by having a facial suture with outwardly bowed preocular
sections.
Order ASAPHIDA Salter, 1864a emend. Fortey and Chatterton, 1988
Superfamily DIKELOCEPHALOIDEA Miller, 1889
Family HUNGAIIDAE Raymond, 1924
Genus Hungaia Walcott, 1914
21
Type species. Dikelocephalus magnificus Billings, 1860; original designation. Upper
Sunwaptan of Quebec.
Remarks. The generic diagnosis of Rasetti (1944) and Ludvigsen et al. (1989) is
followed here.
Hungaia peladensis Rusconi, 1953a
Figure 6.5, 6, 8, 9
1953a. Ungaia peladense Rusconi, p. 8. [Ungaia nom. null.]
1953a. Briscoia peladense Rusconi, p. 7.
1954a. Hungaia peladense Rusconi, Rusconi, p. 12.
Emended diagnosis. A species of Hungaia with slightly tapered, anteriorly rounded
glabella; frontal area with a few delicate, narrow radial caeca; pygidium long, with four
narrow (tr.) pleural furrows that are sub-parallel to axis.
Type material. Pygidium MCNAM 15680 (holotype); cranidium MCNAM 15679
(paratype).
Additional material. Cranidium MCNAM 15675 (Briscoia peladense Rusconi
holotype).
Geographic and stratigraphic provenance. Upper Furongian. El Relincho Formation,
Cerro Pelado locality, Mendoza, Argentina.
Description. Cranidium slightly convex, with rounded anterior margin and concave
frontal area. Glabella gently convex, slightly tapered, anteriorly rounded, widest (tr.) at
S1 furrow, surrounded by narrow and shallow axial and preglabellar furrows; lateral
glabellar furrows weakly developed; S1 better marked, oblique backward, disconnected
at middle and not reaching axial furrows; S2 very faint and short, transverse; occipital
ring short (sag.), approximately one-fifth length of glabella, delimited by a narrow and
shallow occipital furrow which is effaced medially. Frontal area concave and
22
proportionately long (sag.), with a few delicate, narrow radial caeca; anterior branches
of facial suture divergent; palpebral and posterior areas of the fixigena too poorly
preserved for description.
Pygidium long, sub-rectangular in outline. Axis short (sag.), convex, elevated
above pleural fields, very slightly tapered backward and rounded posteriorly,
surrounded by narrow axial furrows which seem to become effaced posteriorly; it is
composed of a short (sag.) articulating half-ring, three axial rings and a terminal piece;
anterior axial ring slightly longer (sag.) than posterior rings. Pleural field flat to
concave, crossed by four long, narrow (tr.) pleural furrows that are sub-parallel to axis;
posterior two pleural furrows shallower than anterior ones; posterior margin of
pygidium imperfectly preserved for description.
Discussion. Because the Borrello collections do not include Hungaia specimens from
Cerro Pelado, the present revision is based only on the fragmentary type material
originally studied by Rusconi (1953a, p. 8). Rusconi provided a brief description of H.
peladensis, pointing out the presence of a large, concave frontal area with delicate radial
caeca, a pygidial axis of four segments, and pleural furrows that are strongly directed
backward. The type specimens are illustrated here for the first time (Fig. 6.5, 6.8, 6.9)
and their diagnosis is emended above. According to Rusconi (1954a, p. 12, 13), H.
peladensis occurs also in the San Isidro area, west of Mendoza city.
In addition, Rusconi (1953a, p. 7) erected Briscoia peladense based on a very
large, incomplete cranidium (holotype MCNAM 15675; Fig. 6.6) from Cerro Pelado.
This late holaspid specimen shows a concave frontal area, a gently convex, slightly
tapered glabella, a rounded preglabellar field, and a backwardly oblique S1 furrow, so it
represents a Hungaia species that is probably conspecific with Hungaia peladensis. It
slightly differs from the paratype cranidium of H. peladensis (Fig. 6.5) by showing a
23
proportionately lower convexity and a fainter S2 glabellar furrow; differences that can
be ascribed to intraspecific variation.
The overall morphology of the type species Hungaia magnifica (Billings, 1860),
from the upper Furongian of Quebec (e.g., Rasetti, 1944, pl. 37, figs. 1–3; Ludvigsen et
al., 1989, pl. 17, figs. 1–3), Maryland (Rasetti, 1959, pl. 54, fig. 15) and western
Newfoundland (Keithia subclavata Fauna; Kindle, 1982, pl. 1.5, fig. 4; Ludvigsen et al.,
1989, pl. 17, figs. 4, 5), is broadly consistent with that of H. peladensis (e.g., both taxa
exhibit a tapered, anteriorly rounded glabella). The former hardly differs by having
conspicuous genal caeca on the frontal area, large bacculae, and wider (tr.) pygidial
pleural furrows.
[Figure 6]
Hungaia burlingi Palmer, from the upper Furongian (Naustia papilio Zone) of
northwest Canada and east-central Alaska (Palmer, 1968, pl. 12, figs. 7–13; Westrop,
1995, pl. 5, figs. 12–14); Hungaia devinei (Billings, 1865), from the upper Furongian of
Quebec (Rasetti, 1944, pl. 37, figs. 4–7, 14, 15; Ludvigsen et al., 1989, pl. 17, figs. 8–
10) and western Newfoundland (Onchonotus richardsoni and Keithia subclavata
faunas; Kindle, 1982, pl. 1.4, fig. 17, pl. 1.5, fig. 3; see Ludvigsen et al., 1989, p. 29, pl.
17, figs. 6, 7, 11); and H. puelchana Rusconi from the upper Furongian of the San Isidro
area, Mendoza (Rusconi, 1953b, figs. 1, 2; 1954a, figs. 2, 3, 12; pl. 1, figs. 2, 3; 1956,
pl. 3, figs. 2, 3; Tortello, in press, figs. 2, 4A–V, 5A–S), constitute a group of species
that can be differentiated from H. peladensis mainly by having a sub-rectangular
glabella. In addition, H. cf. burlingi, from the early Sunwaptan Beothuckia duomenta
Fauna of western Newfoundland (Ludvigsen et al., 1989, pl. 18, figs. 1, 2), is also
distinguished by its shorter and wider pygidium.
24
Hungaia pacifica Kobayashi, 1935, from the upper Furongian of Alaska
(restricted to the fragmentary type pygidia by Palmer, 1968, pl. 12, fig. 14; Kobayashi,
1935, pl. 10, fig. 13), differs from H. peladensis by having a sinuous third pleural
furrow.
Trilobites of uncertain affinities
Although Borrello (1971, p. 407, 409) cited “Parabolinella peladoensis n. sp.”
from Cerro Pelado, this report was not accompanied by any description, illustration nor
typification. Since P. peladoensis fails to conform to Article 13.1 of the International
Code of Zoological Nomenclature (ICZN, 1999), it is regarded as a nomen nudum. No
indication of material of Parabolinella Brøgger, 1882 aspect was found in the Borrello
collections, so the occurrence of this genus in the Argentinian Precordillera is in doubt.
In addition, Rusconi (1951a,b, 1953a) described some rare polymeroids from
Cerro Pelado of uncertain affinities. They are illustrated photographically for the first
time (Figs. 5.7–9, 6.7, 6.10–13) and briefly discussed below, provisionally keeping their
original names.
Prosaukia peladensis Rusconi (1951a, p. 3, 4, fig. 5; 1954b, p. 103) [=Prousakia
peladensis Rusconi; Prousakia Rusconi, 1951a, p. 3, nom. null.] was erected only on the
basis of a fragmentary cranidium (Fig. 6.7), which shows a tapered, anteriorly truncate
glabella with distinct and backwardly directed S1 and S2 furrows; a short (sag.)
preglabellar field; a well developed, convex anterior border; a straight, transverse
anterior margin; faint, backwardly oblique eye ridges; and a sculpture of delicate
granules on the test surface. Sadly, the palpebral lobes are imperfectly preserved for
description. The cranidium of the type species Prosaukia misa (Hall, 1863), from the
Furongian of North America (e.g., Westrop, 1986, pl. 4, figs. 8–14), shares a glabella of
similar outline and pattern of furrows, as well as a narrow (tr.) fixed cheek, but it clearly
25
differs from the specimen studied by having a longer preglabellar field, a less defined
anterior border and a rounded anterior margin. Until more complete material becomes
available for analysis, the affinities of Prosaukia peladensis are doubtful.
Orria peladensis Rusconi (1951a, p. 4, fig. 6; 1954b, p. 103) was based on two
pygidia (Fig. 6.12-right-, 6.13) that are characterized by having a subelliptic outline; a
long and gently tapered axis of seven or eight rings; distinct pleural and interpleural
furrows; and a very narrow, raised border. Four pygidia from the Borrello collection
[MLP 24219(3, 6, 10), 34461; Fig. 5.8–9] show a similar morphology and are regarded
as conspecific. Although this species was originally assigned to the middle Cambrian
genus Orria Walcott, 1916 [= j.s.s. of Bathyuriscus Meek, 1873], Rusconi (1954b)
raised doubts regarding such assignment. Certainly, the pygidia studied bear a closer
resemblance to Neochilonorria Rusconi, 1953b (type species N. coronillensis Rusconi,
1953b, fig. 9; 1954a, pl. 2, fig. 3; 1956, pl. 4, fig. 3), from the Furongian of the San
Isidro area, western Mendoza. Neochilonorria coronillensis is distinguished by having
wider posterior pleural furrows, whereas N. excavata Rusconi (1953c; 1954a, pl. 2, fig.
5) shows a shorter (sag.) and narrower (tr.) axis, as well as more conspicuous pleural
ribs.
Dalmanitina? peladense Rusconi (1953a, p. 7, 8, fig. 10) consists of a type
pygidium (Fig. 6.10) and an additional specimen (Fig. 5.7) that are comparable to that
of “Orria” peladensis. However, the former seem to be shorter (sag.) and less elliptical
in outline.
Finally, Levinia manantialensis Rusconi (1951b, p. 8, 9, fig. 11) was based on a
fragmentary, tiny pygidium (Fig. 6.11) that is characterized by its transversely elongate
outline; a tapered axis with five rings and a blunt terminal piece; five slightly oblique
pleural and interpleural furrows; a narrow, weakly convex pygidial border; and a
26
posterior medial indentation. This pygidium is incomplete but relatively well preserved;
nevertheless, further material is necessary to discuss in detail its systematic affinity.
ACKNOWLEDGEMENTS
Carlos Cingolani (División Geología, Museo de La Plata), Guillermo Campos, Clara
Abal, Susana Devincenzi, Edgardo Aranguez (Museo de Ciencias Naturales y
Antropológicas “Juan Cornelio Moyano”, Mendoza) and Alberto Riccardi (División
Paleozoología Invertebrados, Museo de La Plata) are thanked for making the material
available for study. The reviewers Adrian Rushton and Steve Westrop greatly helped to
improve the manuscript. Miguel Manceñido provided valuable comments on zoological
nomenclature. I also want to thank Mario Campaña, Susana Gomba, Víctor Melemenis
and Norma Valdez for their technical assistance. This research was supported by the
CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), the
Universidad Nacional de La Plata, and the Instituto Superior de Correlación Geológica
(Universidad Nacional de Tucumán - CONICET), Argentina.
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Figure captions
Figure 1. Location map of the fossil locality (asterisk).
Figure 2. 1–28, Lotagnostus peladensis; 1, 5, 6, 8, cephalon in dorsal, lateral, obliqueanterior and posterior views, MLP 34471; 2, cephalon, MLP 24353(5a); 3, 7, 9, 10,
cephalon in dorsal, oblique, posterior and anterior views, MLP 24353(5b); 4, three
cephala and one pygidium, MLP 24352(4); 11, cephalon, MLP 24352(9b); 12,
cephalon, MLP 24352(9a); 13, cephalon, MLP 24234(7); 14, sagittally compressed
cephalon, MLP 24235(1a); 15, latex cast of cephalon, MLP 24233(6a); 16, cephalon,
MLP 24352(4); 17, cephalon, MLP 24233(2a); 18, cephalon, MLP 24233(1); 19, latex
cast of cephalon, MLP 24233(6b); 20, small cephalon, MLP 24219(11); 21, latex cast of
pygidium, MLP 24219(7); 22, pygidium, MLP 24219(2a); 23, distorted, longitudinally
elongated pygidium, MLP 34464; 24, one cephalon (center) and two pygidia, MLP
24352(3); 25, pygidium, MLP 24352(12); 26, pygidium, MLP 34466; 27, small
pygidium, MLP 24353(5c); 28, cephalon (right) and pygidium (left), MLP 24353(6).
All specimens magnified ×5.6. Scale bar = 2 mm.
Figure 3. 1–7, Lotagnostus peladensis; 1, 2, 4, cephalon in oblique, posterior and
anterior views, MLP 24352(9a) (see also Fig. 2.12); 3, pygidium in lateral view, MLP
24233(2b); 5–7, pygidium in dorsal, lateral and posterior views, MLP 24352(10). All
specimens magnified ×5. Scale bar = 2 mm.
Figure 4. 1–4, Pseudorhaptagnostus (Pseudorhaptagnostus) sp.; 1, cephalon, MLP
34467, ×6; 2, pygidium, MLP 24235(1a), ×6; 3, pygidium, MLP 34489, ×6; 4,
39
pygidium (center), MLP 24410(4), ×6.2. 5–25, Mendoparabolina pirquinensis; 5, two
cranidia, MLP 24353(1), ×4.6; 6, incomplete cranidium, MLP 24352(11a), ×4.6; 7,
incomplete cranidium, latex cast, MLP 24352(11b), ×4.6; 8, incomplete cephalon, MLP
24219(8), ×4.6; 9, incomplete cranidium, latex cast, MLP 24233(9), ×4.6; 10,
incomplete cranidium, MLP 24353(9), ×4.6; 11, incomplete cranidium, MLP 34487b,
×4.6; 12, cranidium, MLP 34475, ×4.6; 13, small cranidium, latex cast, MLP
24235(1b), ×4.6; 14, small cranidium, MLP 24352(6b), ×4.6; 15, cranidium (right) and
incomplete pygidium (bottom and left), latex cast, MLP 24235(3), ×4.6; 16, incomplete
cranidium (right) and pygidium (left), latex cast, MLP 24219(1), ×3.5; 17, pygidium,
24219(12b), ×3.5; 18, pygidium, latex cast, MLP 24219(12a), ×3.5; 19, three pygidia,
latex cast, MLP 24353(3a), ×3.5; 20, pygidium, MLP 24219(2b), ×3.5; 21, pygidium,
latex cast, MLP 24235(1c), ×3.5; 22, pygidium, latex cast, MLP 24233(10a), ×3.5; 23,
pygidium, MLP 24235(1a), ×3.5; 24, small pygidium, latex cast, MLP 24233(10b),
×3.5; 25, pygidium, MLP 24352(4), ×3.5. Scale bar = 2 mm.
Figure 5. 1–6, Loganellus cf. macropleurus; 2–4, cranidium in dorsal, lateral and
oblique-anterior views, MLP 24353(4a), ×3.1; 1, 5, 6, pygidium in dorsal, lateral and
posterior views, MLP 34468, ×3. 7, “Dalmanitina?” peladense; pygidium, MLP
24353(3), ×3.9. 8, 9, “Orria” peladensis; 8, fragmentary pygidium, MLP 24219(3),
×4.3; 9, pygidium, latex cast, MLP 24219(6), ×3.9. Scale bar = 4 mm.
Figure 6. Type specimens of polymeroid trilobites from Cerro Pelado described by
Rusconi (1951a,b, 1953a). 1, 2, Mendoparabolina pirquinensis; 1, cranidium,
MCNAM 9709 (holotype), ×2.5; 2, pygidium, MCNAM 9712 (paratype), ×3.1. 3, 4,
Bienvillia? australis; 3, pygidium, MCNAM 9696 (paratype), ×3; 4, cranidium (right)
40
and pygidium (left), MCNAM 9695 (holotype), ×4.1. 5, 6, 8, 9, Hungaia peladensis; 5,
previously unfigured cranidium, MCNAM 15679 (paratype), ×2.1; 6, previously
unfigured cranidium, MCNAM 15675, Briscoia peladense holotype, ×2.1; 8, 9,
previously unfigured pygidium in dorsal and lateral views, MCNAM 15680 (holotype),
×2.2. 7, “Prosaukia” peladensis, cranidium, MCNAM 9702 (holotype), ×2.6. 10,
“Dalmanitina?” peladense, pygidium, MCNAM 15690 (holotype), ×4.8. 11, “Levinia”
manantialensis, pygidium, MCNAM 9929 (holotype), ×3.9. 12, 13, “Orria”
peladensis, pygidium; 12, MCNAM 9726 (holotype) (right) [associated with a
pygidium of Mendoparabolina pirquinensis (left)], ×5.7; 13, MCNAM 9727
(paratype), ×4.5. Scale bar = 4 mm.
41