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A critical re-evaluation of the Late Triassic dinosaur taxa of North America

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The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re-evaluation of saurischian and theropod synapomorphies. Here, we re-evaluate each purported Triassic dinosaur from North America on a specimen by specimen basis using an apomorphy-based approach. We attempt to assign specimens to the most exclusive taxon possible. Our revision of purported Late Triassic dinosaur material from North America indicates that dinosaurs were rarer and less diverse in these strata than previously thought. This analysis concludes that non-dinosaurian dinosauriforms were present in North America in the Late Triassic. Most of the proposed theropod specimens are fragmentary and/or indistinguishable from corresponding elements in the only well-known Triassic theropod of North America, Coelophysis bauri. No Triassic material from North America can be assigned to Sauropodomorpha, because none of the purported ‘prosauropod’ material is diagnostic. Recent discovery of the skull and skeleton of Revueltosaurus callenderi from Arizona shows that it is a pseudosuchian archosaur, not an ornithischian dinosaur. As a result, other purported North American ornithischian teeth cannot be assigned to the Ornithischia and therefore, there are no confirmed North American Triassic ornithischians. Non-tetanuran theropods and possible basal saurischians are the only identifiable dinosaurs recognised in North America until the beginning of the Jurassic Period.
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Journal of Systematic Palaeontology 5(2): 209–243 Issued 25 May 2007
doi:10.1017/S1477201907002040 Printed in the United Kingdom C
The Natural History Museum
A critical re-evaluation of the Late
Triassic dinosaur taxa of North
America
Sterling J. Nesbitt
American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA and
Lamont-Doherty Earth Observatory, Columbia University, 61 Rt. 9W, Palisades, NY 10964, USA
Randall B. Irmis
Museum of Paleontology and Department of Integrative Biology, 1101 Valley Life Sciences Building,
University of California, Berkeley, CA 94720–4780, USA
William G. Parker
Division of Resource Management, Petrified Forest National Park, P.O. Box 2217, Petrified Forest,
AZ 86028, USA
SYNOPSIS The North American Triassic dinosaur record has been repeatedly cited as one of the most
complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition
that Herrerasaurus and Eoraptor may not be theropods have forced a re-evaluation of saurischian
and theropod synapomorphies. Here, we re-evaluate each purported Triassic dinosaur from North
America on a specimen by specimen basis using an apomorphy-based approach. We attempt to assign
specimens to the most exclusive taxon possible. Our revision of purported Late Triassic dinosaur
material from North America indicates that dinosaurs were rarer and less diverse in these strata
than previously thought. This analysis concludes that non-dinosaurian dinosauriforms were present
in North America in the Late Triassic. Most of the proposed theropod specimens are fragmentary
and/or indistinguishable from corresponding elements in the only well-known Triassic theropod
of North America, Coelophysis bauri. No Triassic material from North America can be assigned to
Sauropodomorpha, because none of the purported ‘prosauropod’ material is diagnostic. Recent
discovery of the skull and skeleton of Revueltosaurus callenderi from Arizona shows that it is a
pseudosuchian archosaur, not an ornithischian dinosaur. As a result, other purported North American
ornithischian teeth cannot be assigned to the Ornithischia and therefore, there are no confirmed
North American Triassic ornithischians. Non-tetanuran theropods and possible basal saurischians
are the only identifiable dinosaurs recognised in North America until the beginning of the Jurassic
Period.
KEY WORDS Dinosauria, Ornithischia, Saurischia, Theropoda, Triassic, early diversity
Contents
Introduction 210
Methods 210
Institutional Abbreviations 211
Putative theropods 211
New Mexico 211
Eucoelophysis baldwini Sullivan & Lucas, 1999 211
Snyder Quarry ‘dinosaur’ material 214
Coelophysis bauri Cope, 1889 218
Coelophysis material of Cope 220
Gojirasaurus quayi Carpenter, 1997 220
Bluewater Creek Member ‘theropod’ material 222
Santa Rosa Formation ‘theropod’ material 222
Arizona 222
Coelophysis sp. (Padian, 1986) 222
‘Camposaurus arizonensis’ Hunt et al., 1998 222
Other Placerias Quarry material 223
Texas 223
Protoavis texensis Chatterjee, 1991 223
210 S. J. Nesbitt et al.
Shuvosaurus inexpectatus Chatterjee, 1993 224
Spinosuchus caseanus von Huene, 1932 225
Putative herrerasaurids 225
Caseosaurus crosbyensis Hunt et al., 1998 225
Chindesaurus bryansmalli Long & Murry, 1995 226
NMMNH P-4569 229
NMMNH P-17375 229
Arctosaurus osborni Adams, 1875 229
Putative ornithischians 230
Technosaurus smalli Chatterjee, 1984 230
TTUP unnumbered 232
Putative ‘prosauropods’ 232
Discussion 233
Other evidence 234
Timing of the early diversity of dinosaurs in North America 235
The Triassic record outside North America 236
Conclusions 237
Acknowledgements 237
References 237
Appendix 242
Introduction
The origin of the Dinosauria lies in the Late Triassic Period
(Gauthier 1986; Langer 2004; Langer & Benton 2006): how-
ever, our understanding of the early history and relationships
of dinosaurs remains poor because of the absence of well
preserved crania and postcrania for most basal dinosaurs and
a poor understanding of the character polarities of dinosaurs
and their immediate outgroups (Fraser et al. 2002). Further-
more, a lack of consensus of the phylogenetic placement of
controversial taxa such as Herrerasaurus inside Theropoda
(Sereno & Novas 1993; Novas 1993), as a stem saurischian
(Langer 2004) or outside Dinosauria (Holtz & Padian 1995;
Fraser et al. 2002)) hampers our understanding of the ori-
gin, early biogeography and diversity of the Dinosauria. A
new distribution of character states among ornithodirans and
basal archosaurs (including crocodile-line archosaurs) has
emerged with the discovery of taxa such as Silesaurus (Dzik
2003), Effigia okeeffeae (Nesbitt & Norell 2006) and Re-
vueltosaurus (Parker et al. 2005) and has led to new insights
regarding the identification of crocodile-line archosaurs, or-
nithodirans, dinosauromorphs, dinosauriforms and members
of the Dinosauria in the Triassic.
Recently, many Late Triassic dinosaur specimens have
been described from around the world (see Heckert & Lucas
2000), especially from the western United States (Hunt 1991;
Carpenter 1997; Hunt et al. 1998; Sullivan & Lucas 1999;
Heckert & Lucas 2000). The apparently high diversity of
dinosaurs in the western United States (Hunt et al. 1998) has
been compared with the European (Rauhut & Hungerb¨
uhler
2000) and South American (Heckert & Lucas 2000) Triassic
dinosaur faunas.
Here, we re-examine each purported Triassic dinosaur
from North America on a specimen by specimen basis. We
employ a conservative approach in our assignments to spe-
cific or more general clades that are unaffected by the various
current phylogenetic hypotheses concerning the placement
of controversial taxa (e.g. Eoraptor and Herrerasaurus). Our
goal in this study is to determine which specimens in the
Late Triassic of North America can be unambiguously iden-
tified as members of Dinosauria. We do not specify the exact
phylogenetic position of these taxa within Dinosauria, a task
that requires a comprehensive specimen-based phylogenetic
analysis that is beyond the scope of the present work.
Methods
Revision of the diagnoses of Dinosauromorpha, Dinosauri-
formes and Dinosauria is beyond the scope of this paper
and can only be completed after a comprehensive phylogen-
etic analysis. Because there is no consensus regarding the
diagnosis of Dinosauria (see Sereno & Novas 1993; Sereno
1999; Holtz & Padian 1995; Fraser et al. 2002; Langer &-
Benton 2006) and its immediate outgroups, we use an
apomorphy-based approach. That is, we use specimen by spe-
cimen comparisons and highlight character states that have
previously been used in phylogenetic analyses to place taxa
within specific clades. We cannot always assign a specimen
to a species-level taxon, so we assign specimens to the least
inclusive clade possible using apomorphies. The most useful
character states for identification of members of Dinosauria
are illustrated in Fig. 1.
We recognise that some of the taxa considered here
may fall within the Dinosauria in future phylogenetic ana-
lyses; however, the lack of certain character states that place
a taxon within Dinosauria may be a result of reversals (e.g.
a nearly closed acetabulum) and/or missing data in other
important regions of the body (e.g. the skull of Chindes-
aurus is not known), as exemplified by many of the purpor-
ted Late Triassic dinosaurs of North America. Only after a
rigorous phylogenetic analysis, which is not provided herein,
Re-evaluation of North American Late Triassic dinosaur taxa 211
Figure 1 Dinosaur specimens displaying character states used to
diagnose Dinosauria in the text. (A) left ilium of the holotype of
Dilophosaurus wetherilli (UCMP 37302) in posterior view showing the
brevis fossa. Left proximal femur of Coelophysis sp. (UCMP 129618) in
anterior (B), posterior (C) and proximal (D) views, showing the
presence of a spike-like anterior trochanter, offset head and ligament
sulcus. (E) right distal tibia of Coelophysis sp. (UCMP 129618) in
anterior view showing an expanded lateral process. (F) left
astragalocalcaneum of Coelophysis bauri (AMNH FR30576) displaying
a posterior basin adjacent to the ascending process of the astragalus.
Abbreviations: ac, acetabulum; ap, ascending process; ar, acetabular
rim; at, anterior trochanter; bf, brevis fossa; cn, calcaneum; faa, facies
articularis antitrochanterica; ib, iliac blade; ip, ischial peduncle; lp,
lateral process; ls, ligament sulcus; oh, offset head; pb, posterior
basin; plr, posterolateral ridge; ts, trochanteric shelf.
can these ambiguous cases be settled. It is important to take
this conservative approach with such specimens and it would
be imprudent to consider specimens lacking key dinosaurian
character states to be true dinosaurs. Such an approach in
the past has inflated the record of Triassic dinosaurs in North
America.
In this study, Saturnalia is considered to be a basal
sauropodomorph, following recent phylogenetic studies (e.g.
Langer 2004; Yates 2004). We provisionally agree with
Langer & Benton (2006) that Herrerasaurus and Eoraptor
are basal saurischians based on our own observation of the
material, but this hypothesis requires further testing. There
is still a possibility that Herrerasaurus and Eoraptor could
fall outside Dinosauria sensu stricto (e.g. Holtz & Padian
1995), but in Langer (2004), constraining these two taxa to
fall outside of the Dinosauria resulted in a most parsimonious
tree 14 steps longer than the unconstrained tree that placed
them as basal saurischians and 12 steps longer than a tree
constraining them to be within Theropoda. Most relevant to
this study, Herrerasaurus shares several pelvic and hindlimb
character states with other saurischians that are not found in
basal ornithischians (Langer 2004; Langer & Benton 2006).
We have studied first-hand Marasuchus,Lagerpeton,
Pseudolagosuchus,Agnostiphys,Scutellosaurus,Eoraptor,
Herrerasaurus,Guaibasaurus,Saturnalia,Unaysaurus,Ri-
ojasaurus,Coelophysis bauri,Coelophysis sp., Dilopho-
saurus, Silesaurus and all of the specimens being revised
below with the exception of Arctosaurus.CastsofLeso-
thosaurus tibiae described by Knoll & Battail (2001) were
also examined. Descriptions of Lesothosaurus,Thecodonto-
saurus,Plateosaurus,Coelophysis rhodesiensis,‘Syntarsus
kayentakatae,Liliensternus and Arctosaurus were taken from
the literature. Unpublished photographs of Silesaurus mater-
ial were also used.
Institutional Abbreviations
AMNH, American Museum of Natural History, New York,
NY; FMNH, Field Museum of Natural History, Chicago, IL;
MNA, Museum of Northern Arizona, Flagstaff, AZ; NMI,
National Museum of Ireland; NMMNH, New Mexico Mu-
seum of Natural History, Albuquerque, NM; PEFO,Petri-
fied Forest National Park, AZ; TTUP, Texas Tech University
Paleontology Collections, Lubbock, TX; UCM, University
of Colorado Museum, Boulder, CO; UCMP, University of
California Museum of Paleontology, Berkeley, CA; UMMP,
University of Michigan Museum of Paleontology, Ann Ar-
bor, MI; YPM, Yale Peabody Museum, New Haven, CT.
Putative theropods
New Mexico
Eucoelophysis baldwini Sullivan & Lucas, 1999
(Fig. 2)
AGE.Norian, Late Triassic.
OCCURRENCE.Petrified Forest Member, Chinle Formation
(Sullivan et al. 1996; Sullivan & Lucas 1999), Rio Arriba
County, New Mexico, U.S.A.
HOLOTYPE.NMNNH P-22298 (Figs 2A–E).
REFERRED MATERIAL.Sullivan & Lucas (1999) referred a
pubis (AMNH 2706), part of the syntype of Coelophysis
longicollis (see Padian 1986), to E. baldwini.
TAXONOMIC ASSIGNMENT.Non-dinosaurian basal orni-
thodiran.
REMARKS.The holotype specimen of Eucoelophysis bald-
wini (Sullivan & Lucas 1999) was collected from a small
quarry with a mixed assemblage including Typothorax,rep-
resented by an osteoderm and other numerous unidentifi-
able fragments. Sullivan & Lucas (1999) assigned most of
the material to Eucoelophysis based on its proximity to the
partially articulated hindlimbs and stated that the scapula
may belong to another taxon. They also assigned a pu-
bis from Cope’s original material of Coelophysis to Eu-
coelophysis based on arguments that it was collected near
the type locality of Eucoelophysis and the presence of an
apomorphy tying it to the pubis assigned to the holotype of
Eucoelophysis. Originally described as a coelophysoid thero-
pod dinosaur, our re-examination of the holotype and com-
parisons with other Triassic archosaurs (e.g. Silesaurus), sug-
gest that Eucoelophysis is not a coelophysoid and not even a
dinosaur.
Sullivan & Lucas (1999) used two characters to as-
sign Eucoelophysis to the Ceratosauria (sensu Rowe & Gau-
thier 1990): (1) the presence of triangular and posteriorly-
directed transverse processes of the dorsal vertebrae and (2)
212 S. J. Nesbitt et al.
Figure 2 Informative elements from the holotype of Eucoelophysis baldwini (NMMNM P-22298). The right tibia in proximal (A) and medial (B)
views and the left femur in proximal (C), posterior (D) and anterior (E) views. Posterorventral portion of the right ilium in lateral (F) and ventral
(G) views. The dashed lines postulate the extrapolation of the finished edges and the small arrow indicates the anterior direction. Proximal
portion of the femur of PEFO 34347 in dorsal (H), lateral (I) and medial (J) views. Abbreviations: ac, acetabulum; at, anterior trochanter; cc,
cnemial crest; dlt, dorsolateral trochanter; fn, femoral head notch; fr, fragments; ip, ischiadic process; mpt, mediolateral proximal tuber; pg,
proximal groove; Scale bars =1cm.
the presence of a prominent trochanteric shelf on the anterior
trochanter of the femur. The first character is not present in
the specimen. The vertebrae that Sullivan & Lucas (1999)
identified as dorsal vertebrae are actually posterior cervical
vertebrae, because they preserve parapophyses on the ventro-
lateral sides of the anterior portion of the centrum. The trans-
verse processes of the best preserved cervical are laterally
directed and not backswept as in coelophysoids. Second, an
isolated neural arch, identified by Sullivan & Lucas (1999) as
possibly belonging to a dorsal vertebra, bears processes that
are also laterally directed and obscured by matrix in dorsal
view. Therefore, none of the vertebrae have triangular, back-
swept, posteriorly-directed transverse processes. A prom-
inent anteroposteriorly orientated trochanteric shelf on the
anterior trochanter of the femur occurs in some coelophys-
oids and Ceratosaurus (Rowe & Gauthier 1990); however,
there is no prominent trochanteric shelf on either of the holo-
type femora of Eucoelophysis. The anterior trochanter is a
simple spike-like projection (Fig. 2E). Nevertheless, the pres-
ence of a trochanteric shelf has a wider distribution in basal
Dinosauria and is found in basal taxa such as Herrerasaurus
(Novas 1993) and Saturnalia (Langer 2003).
Both Eucoelophysis femora have a small dorsolat-
eral trochanter (=dlt, dorsolateral trochanter in Fig. 2)
just posterolateral to the anterior trochanter. This same
expansion is present in Herrerasaurus and Chindesaurus
(Bonaparte et al. 1999; Langer 2003). In addition, the
distal end of the femur of Eucoelophysis lacks a sulcus
between the lateral and fibular distal condyles, which is
found in most basal theropods (Rowe & Gauthier 1990)
and a variety of other archosaurian taxa such as Sat-
urnalia,Silesaurus,Shuvosaurus and Dibothrosuchus (Wu &
Chatterjee 1993). Without these last two crucial characters,
Eucoelophysis shares no character states with coelophysoids
and, thus, cannot be assigned to the coelophysoid or ‘cerato-
saurid’ clade.
Moreover, Eucoelophysis cannot be assigned to the Di-
nosauria because it lacks characters shared by both sauris-
chians and ornithischians. Dinosaurs have a distinct prox-
imal femur with an offset femoral head (Novas 1989) and a
Re-evaluation of North American Late Triassic dinosaur taxa 213
prominent facies articularis antitrochanterica (see Langer
2004). The femur of Eucoelophysis lacks both of these char-
acters (Figs 2C–E). Instead, the femoral head is roughly tri-
angular in lateral view as in Silesaurus (Dzik 2003). The
only character that the femora of Eucoelophysis shares with
the Dinosauria is the presence of an anterior trochanter
with a spike-like projection; however, taxa outside the Dino-
sauria such as Silesaurus andeventhesuchianOrnithosuchus
(Walker 1964; Sereno 1991) all have similar spike-like an-
terior trochanters. The proximal head of the femur of Eu-
coelophysis is triangular in proximal view and has a me-
diolaterally trending sulcus that Sullivan & Lucas (1999)
considered an autapomorphy. This sulcus is not unique to
Eucoelophysis and is present in other archosaurs such as
Silesaurus,Saturnalia,Coelophysis sp. (Padian 1986), Popo-
saurus,Ornithosuchus and juvenile phytosaurs and aetosaurs
(S.J.N., pers. obs.).
The proximal portion of the tibia (Figs 2A,B) is nearly
featureless, but has a cnemial crest (Sullivan & Lucas 1999), a
character that is shared among ornithodirans, including those
outside the Dinosauria (e.g. Marasuchus). The appressed sur-
face of the tibia that Sullivan & Lucas (1999) described is
unique to Eucoelophysis; however, the homology of the ap-
pressed surfaces of the tibiae of both Eucoelophysis and the
small Snyder Quarry coelophysoid advocated by Heckert et
al. (2000b, 2003) is doubtful because the length and morpho-
logy of each of the specimens are different from one another.
The holotype includes a partial right metatarsus with
most of metatarsal II (missing the proximal end), a nearly
complete metatarsal III and the distal portion of metatarsal IV.
The proximal end of metatarsal III is symmetrical and similar
to other basal ornithodirans and dinosaurs. The distal artic-
ular end of metatarsal IV is asymmetrical and deeper than
broad, an apomorphic state shared with Saturnalia,thero-
pods and some ornithopods (Langer 2003, 2004; Langer &
Benton 2006). Dzik (2003) did not figure or describe the
distal end of metatarsal IV for Silesaurus, so it is unclear
what character state is present in Silesaurus.
Because the hindlimbs were the only elements of Eu-
coelophysis that were definitely associated (within a multi-
taxic quarry), we consider the hindlimbs and metatarsals to
be the only definite material pertaining to the holotype of Eu-
coelophysis. The other elements may or may not pertain to
Eucoelophysis and, as discussed below, are non-diagnostic.
The proximal surface of the pubis assigned to Eu-
coelophysis bears an ischio-acetabular groove between the
ischial facet and the acetabular facet, which Sullivan &
Lucas (1999) considered to be an autapomorphy of the taxon;
however, an ischio-acetabular groove is also present in Sat-
urnalia (Langer 2003). Examination of the holotype and
paratypes of Saturnalia indicates that the ischio-acetabular
groove in this taxon differs slightly from the Eucoelophysis
pubis in not piercing the medial wall of the pubis, whereas
the groove in Eucoelophysis completely pierces both the lat-
eral and medial margins of the pubis. The ischio-acetabular
groove used by Sullivan & Lucas (1999) to refer a pubis
from the original syntypes of Coelophysis bauri (AMNH
2706) to Eucoelophysis is much shallower, does not pierce
the medial wall of the pubis (similar to Saturnalia)andis
poorly defined relative to the condition in the holotype of
Eucoelophysis. Recent repreparation of this pubis (AMNH
2706) also indicates the presence of both an obturator fora-
men and pubic foramen, a coelophysoid theropod character.
We could not determine if the pubis included with the holo-
type of Eucoelophysis also has a pubic foramen. Therefore,
the original syntype of Coelophysis most probably does not
contain Eucoelophysis material (i.e. material assignable to
the same taxon as the himdlimb material of the holotype of
Eucoelophysis).
Furthermore, we do not agree with Sullivan & Lucas’s
(1999) interpretation of the pubis, particularly regarding their
identifications of the iliac, ischial and acetabular facets. After
a close inspection of the proximal end of the pubis, these
three regions cannot be clearly discerned because of the poor
preservation of the proximal end. Moreover, the assignment
of the acetabular facet implies that Eucoelophysis has an
open acetabulum: however, the proximal face of the pubis is
poorly preserved, so it is not certain if the acetabulum was
open. A previously undescribed fragment of the ischiadic
process of an ilium (Figs 2F, G) discovered with the type
material suggests that if all the pelvic material belongs to
Eucoelophysis, the acetabulum was mostly or completely
closed. Even if the assignment of the three articular surfaces
of the proximal surface of the pubis by Sullivan & Lucas
(1999) is correct, it is not clear that the pubis found with
the hindlimbs of Eucoelophysis belongs to the same taxon
because it was not found in articulation and other taxa are
known from the quarry.
Regardless of whether the bone Sullivan & Lucas (1999)
identified as the ischium is referable to Eucoelophysis, it does
not belong to a dinosaur. The ischium lacks an articular facet
with the pubis and does not indicate an open acetabulum.
The right scapulacoracoid assigned to the holotype of
Eucoelophysis is missing the distal end of the scapula and
ventral portion of the coracoid as well as most of the anterior
margin of both bones. The small portion of the coracoid
seems to be firmly sutured to the scapula as described by
Sullivan & Lucas (1999). It is a robust element, but lacks any
informative character states except that it appears to have
a fully posteriorly directed glenoid fossa, a character state
present in dinosaurs (Fraser et al. 2002).
In summary, the hindlimb elements preserved in the
holotype specimen indicate that Eucoelophysis is neither a
theropod nor a dinosaur because it shares no apomorphies
with these taxa. The morphology and more medial place-
ment of the fourth trochanter and the presence of the an-
terior trochanter of the femur does indicate that the taxon
is more closely related to Dinosauria than to Crocodylo-
morpha, but, at the moment, the placement of Eucoelophysis
in a phylogenetic framework is hampered for two reasons:
(1) the holotype of Eucoelophysis lacks substantial inform-
ation because it is incomplete and (2) basal archosaur rela-
tionships are in a state of flux (Gower & Wilkinson 1996).
The preserved elements closely resemble Silesaurus, an un-
ambiguous ornithodiran from the Carnian of Poland (Dzik
2003) and Pseudolagosuchus from the Middle Triassic of Ar-
gentina. All three taxa share the presence of a small femoral
head that is triangular in proximal view and the absence of
a facies articularis antitrochanterica (Figs 2 C–E), two char-
acter states that are derived relative to other ornithodirans. A
third possible synapomorphy shared by Eucoelophysis,Sile-
saurus and Pseudolagosuchus is a non-offset femoral head
defined by a small ventral emargination visible in anterior and
posterior views (Figs 2 C–E). In addition, Silesaurus and Eu-
coelophysis share a deep proximal sulcus and a finger-like an-
terior trochanter. The anterior trochanter is not visible in the
214 S. J. Nesbitt et al.
holotype of Pseudolagosuchus. The presence of an anterior
trochanteric shelf separates Eucoelophysis from Silesaurus;
however, not all Silesaurus femora have a trochanteric shelf.
In addition, Novas (1992: fig. 4B) illustrates a trochanteric
shelf for a referred specimen of Pseudolagosuchus.Eu-
coelophysis,Silesaurus and Pseudolagosuchus also share a
well-defined, sharp dorsolateral trochanter (Figs 2C, E) on
the proximal portion of the femur. The absence of dinosaurian
femoral characters and the presence of ornithodiran femoral
characters (presence of an anterior trochanter) suggest that
both Eucoelophysis and Silesaurus are non-dinosaurian or-
nithodirans, as has also been hypothesised for Pseudola-
gosuchus (Arcucci 1987; Novas 1992). In addition, the con-
tinuation of the division of the distal femoral condyles one-
third up the shaft, a character absent in other ornithodiran
taxa, is present in both Silesaurus and Eucoelophysis.The
distal end of the femur of Pseudolagosuchus is too poorly
preserved to evaluate this character in that taxon.
The pubes of Silesaurus and Pseudolagosuchus are
nearly identical, but they differ substantially from the pubis
found with the holotype of Eucoelophysis, which is gracile
and rod-like. This suggests that the pubis found with Eu-
coelophysis may not belong to this taxon because the holo-
type was found among other archosaurian remains and was
not articulated with the other bones of the Eucoelophysis
holotype.
The other elements that cannot be shown to belong
with the hindlimbs of Eucoelophysis (because the mixed
assemblage confuses possible associations) and therefore
might pertain to Eucoelophysis, another dinosaur or dino-
saurs, or one or more basal archosaurs, are the ischium,
scapula and the vertebrae.
In conclusion, we consider Eucoelophysis to represent
a valid taxon because it processes one autapomorphy, an
appressed surface of the tibia. Based on preserved character
states in the hindlimb elements, we can assign Eucoelophysis
to a non-dinosaurian basal ornithodiran. Based on several
potential synapomorphies and other shared characters in the
femur, we hypothesise that Eucoelophysis,Silesaurus and
Pseudolagosuchus may form a group of basal dinosauriforms
close to, but outside, Dinosauria. This hypothesis requires
further testing in an explicit phylogenetic context.
Two other specimens referable to the possible clade
containing Eucoelophysis,Silesaurus and Pseudolagosuchus
are a complete femur (TMM 31100–185) from the Dockum
Group (Otis Chalk quarry 3) of Texas and a well preserved
proximal portion of a femur (PEFO 34347) (Figs 2F–G)
from the Blue Mesa Member (Chinle Formation) in Petrified
Forest National Park, Arizona. First described as a possible
ornithosuchian (Long & Murry 1995), the complete femur
(TMM 31100–185) has the same derived character states
present (i.e. a proximal groove, a small notched offset femoral
head that is triangular in proximal view and a well-defined
dorsolateral trochanter) as in Eucoelophysis,Silesaurus and
Pseudolagosuchus. The proximal portion of the femur from
the Petrified Forest also preserves the same suite of derived
character states. Unfortunately, the anterior trochanter is not
preserved in this specimen. The well-defined dorsolateral
trochanter is much more pronounced in PEFO 34347 than
in Eucoelophysis and PEFO 34347 has a slight, but more
pronounced mediolateral proximal tuber in comparison with
Eucoelophysis (Fig. 2F). The mediolateral proximal tuber is
present plesiomorphically in all members of the Archosauria.
The stratigraphic position of both PEFO 34347 and TMM
31100-185 suggest that members of the Eucoelophysis,Sile-
saurus and Pseudolagosuchus clade were present at the base
of the Chinle Formation and in the Dockum Group (if the
stratigraphy for the Dockum in Texas proposed by Lucas &
Anderson (1993) is correct; but see Lehman & Chatterjee
(2005) for an alternative interpretation).
Snyder Quarry ‘dinosaur’ material (Fig. 3)
AGE.Norian, Late Triassic.
OCCURRENCE.Petrified Forest Member, Chinle Formation
(Lucas et al. 2003), Rio Arriba County, New Mexico, USA.
SPECIMENS.NMMNH P-30852, left premaxilla, left max-
illa, right lacrimal, both dentaries and surangulars, left
splenial, hyoid elements and two articulated anterior cer-
vical vertebrae and cervical ribs; NMMNH P-30779, dorsal
vertebra; NMMNH P-30780, dorsal vertebra; NMMNH
P-33691, dorsal vertebra; NMMNH P-31661, sacrum;
NMMNH P-31661, partial left scapulocoracoid; NMMNH
P-29047, partial right ilium, nearly complete right ischium,
and proximal tibia; NMMNH P-29046, right and left femora,
complete tibia and proximal tibia and fibula; NMMNH P-
31293, nearly complete left tibia; NMMNH P-29168, large
tibia, fibula with fused astragalocalcaneum.
TAXONOMIC PLACEMENT.Two, possibly three distinct orni-
thodirans that are not referable to Eucoelophysis.
REMARKS.The Snyder Quarry contains a multitaxic as-
semblage of Norian vertebrates that is roughly stratigraph-
ically equivalent to the nearby Canjilon Quarry and strati-
graphically well below the famous Ghost Ranch Coelophysis
Quarry (Zeigler et al. 2003). During the excavation of nu-
merous phytosaur and aetosaur specimens, several disartic-
ulated dinosaur-like elements were recovered. Heckert et al.
(2000b, 2003) assigned all the dinosaur material from the
quarry to Eucoelophysis sp. except one specimen, which
they considered to represent an unnamed large coelophys-
oid (NMMNH P-29168). A portion of some of the smaller
material was associated and may belong to one individual
(NMMNH P-29046. Heckert et al. 2000b).
It was assumed by the original authors that all mater-
ial of roughly the same size belonged to the same taxon.
Our re-examination of the material suggests that at least two
coelophysoids are present (one large and one small that may
or may not be the same taxon), as well as a third taxon closely
related to, but possibly outside of, Dinosauria.
Heckert et al. (2000b, 2003) assigned the majority of
the material to Eucoelophysis based on the similarity of the
scapulocoracoid, ischium and an appressed lateral surface of
the tibia. This referral is faulty for several reasons. Firstly,
the similarities of the scapula between the small Snyder
quarry theropod and Eucoelophysis are found in all arch-
osauriforms. Secondly, the ischium of Eucoelophysis is not
typical of any dinosaur because it lacks a rim defining the
acetabulum and a distinct articular surface with the pubis;
it may not even belong with the rest of the holotype of Eu-
coelophysis as discussed above. Conversely, the ischium of
the small Snyder quarry theropod clearly has a rim defin-
ing the open acetabulum and a clear articulation with the
pubis. Thirdly, as mentioned previously, the lateral position
of the appressed surface of the Eucoelophysis tibia cannot
Re-evaluation of North American Late Triassic dinosaur taxa 215
Figure 3 Informative elements from the Snyder Quarry coelophysoid. Left femur (NMMNH P-29046) in proximal (A), posterior (B), anterior
(C) and distal (D) views. Left tibia (NMMNH P-29046) in proximal (E), posterior (F), anterior (G) and distal (H) views. Anterior portion of a right
ilium (NMNNH P-29047) in lateral (I) view. Fused sacrum (NMMNH P-31661) in lateral (J) view. Nearly complete right ischium (NMMNH P-29047)
in lateral (K) view. Abbreviations: ac, acetabulum; at, anterior trochanter; cc, cnemial crest; faa, facies articularis antitrochanterica;
fc, fibular crest of the tibia; g, groove; le, lateral expansion of the distal portion of the tibia; pp, pubic peduncle; 4t, fourth trocenter. Scale
bars =1cm.
216 S. J. Nesbitt et al.
be considered homologous to the appressed lateral surface
of the tibia of the small Snyder Quarry theropod. Heckert
et al. (2000b, 2003) highlighted the major differences (e.g.
difference in the proximal portion of the head) between the
femora of Eucoelophysis and the Snyder Quarry theropod,
but failed to recognise the importance of these differences.
As mentioned previously, several characters of the proximal
femur of Eucoelophysis preclude an assignment to the Di-
nosauria, whereas femora from the Snyder Quarry theropod
are consistent with those of coelophysoids. Thus, in light of
our reappraisal of the holotype of Eucoelophysis, the referral
of the small coelophysoid material to Eucoelophysis is not
tenable.
Most of the small Snyder Quarry theropod speci-
mens (Figs 3A–I) appear to belong to at least two associ-
ated individuals (NMMNH P-30852, NMMNH P-29047 and
NMMNH P-29046) of a coelophysoid similar to Coelophysis
bauri and Coelophysis rhodesiensis. The preserved skull
material (NMMNH P-30852) can be identified as a non-
tetanuran theropod based on the presence of a sub-narial gap
between the premaxilla and maxilla. This character may be a
synapomorphy of Coelophysoidea (Rowe & Gauthier 1990),
although recent analyses suggest that Dilophosaurus,which
also has this character state, may be closer to Ceratosauria
than to Coelophysidae (Carrano et al. 2002; Rauhut 2003).
Traditionally, the L-shaped’ lacrimal that is visible in dorsal
view (present in the Snyder Quarry specimen) has been used
as a dinosaur synapomorphy (e.g. Gauthier 1986), but Rauhut
(2003) recognised that other basal archosaurs have a lacrimal
exposed in dorsal view.
The cervical vertebrae found in direct association with
the skull are clearly theropod, because they have two elongate
pleurocoels on the lateral surface of the centrum (one on the
anterior centrum and one on the posterior centrum), which
are found in Coelophysis and other non-tetanuran theropods.
A variety of limb and girdle elements probably per-
tain to the small coelophysoid taxon. The scapulocoracoid
(NMMNH P-31661) has a visible suture between the two
elements. This suture closes during ontogeny in coelophys-
oids (Tykoski & Rowe 2004) and other archosaurs (Brochu
1995). The strap-like morphology of the scapular blade in
this specimen is found in many theropods (Rauhut 2003) as
well as Eoraptor (Sereno et al. 1993) and Herrerasaurus
(Sereno 1993), but it is unclear if the distal end is expan-
ded as in coelophysoids (Tykoski & Rowe 2004) and Sat-
urnalia (Langer et al. 1999), because this is not preserved.
The sacrum (Fig. 3J: NMMNH P-31661) also appears to
be from a coelophysoid theropod. It has four fused sacral
vertebrae and a caudo-sacral (five sacrals total) that artic-
ulated with the ilium. Having at least three sacral verteb-
rae is generally considered diagnostic of Dinosauria (Fraser
et al. 2002), but the suchians Sillosuchus and Shuvosaurus
also have at least four sacral vertebrae plus additional dorso-
sacral vertebrae. The pattern of attachment to the ilium and
gracile morphology of the sacral ribs in the Snyder Quarry
sacrum is nearly identical to Coelophysis bauri, but dif-
fers from Saturnalia,Caseosaurus,Herrerasaurus,Eorap-
tor,Silesaurus,Poposaurus,Sillosuchus and Shuvosaurus.
NMMNH P-29047 includes a partial ilium with a fully open
acetabulum (Fig. 3I) and an enlarged overhanging supra-
acetabular rim. This enlarged rim is present in coelophyso-
ids (e.g. Coelophysis sp. (Padian 1986), Coelophysis bauri,
Syntarsus’ kayentakatae and Segisaurus) as well as many
other non-avian theropods (Rauhut 2003). The ischium
(Fig. 3K) of NMMNH P-29047 is similar to other coelophys-
oids such as Coelophysis bauri and Syntarsus’ kayentakatae
in that the pubic peduncle of the ischium is part of an elongate
process separated from the iliac articulation of the ischium.
This character is not present in Herrerasaurus (Novas 1993),
or Saturnalia (Langer 2003), but is present in Coelophysis
bauri,‘Syntarsuskayentakatae,Coelophysis rhodesiensis
and some tetanuran theropods (Rauhut 2003). The anterior
border of the proximal ischium is broken, so the position and
morphology of the obturator process (Rauhut 2003) cannot
be determined. The distal portion of the ischium ends in a
small, but distinct posteriorly directed foot. This is similar
to the condition in Saturnalia (Langer 2003), Coelophysis
rhodesiensis (Raath 1969), Segisaurus halli (Camp 1936)
and Allosaurus (Madsen 1976), whereas Coelophysis sp.
(Padian 1986), Coelophysis bauri (Colbert 1989) and Syn-
tarsuskayentakatae (Tykoski 1998) have a small symmet-
rical ‘knob.’
The femora of NMMNH P-29046 (Figs 3A–D) have
an offset femoral head and spike-like anterior trochanter
separated from the femoral shaft, both of which are syn-
apomorphies for Dinosauria. A distinct trochanteric shelf
is present adjacent to the anterior trochanter as in Sile-
saurus (Dzik 2003), Herrerasaurus (Novas 1993), Chindes-
aurus (this study), Saturnalia (Langer 2003), Coelophysis
sp. (Padian 1986), Coelophysis bauri and other basal thero-
pods (Rauhut 2003). The dorsolateral trochanter forms a
distinct ridge as in Saturnalia (Langer 2003), Coelophysis
sp. (Padian 1986), Coelophysis bauri and other theropods.
The fourth trochanter forms a low ridge with a ventral bor-
der that gradually grades into the shaft as with Silesaurus
(Dzik 2003), Coelophysis sp. (Padian 1986) and Coelophysis
bauri.InHerrerasaurus (Novas 1993), Saturnalia (Langer
2003) and other basal sauropodomorphs, the ventral bor-
der of the fourth trochanter terminates abruptly and is per-
pendicular to the femoral shaft. The distal femur of the
small Snyder Quarry coelophysoid is similar to Silesaurus
(Dzik 2003), Saturnalia (Langer 2003), Coelophysis sp.
(Padian 1986), Coelophysis bauri and Syntarsuskayen-
takatae (among other basal theropods) in having a differenti-
ated lateral and fibular condyle that is separated by a distinct
sulcus.
Three small coelophysoid-like tibiae (NMMNH P-
29046, NMMNH P-29047 and NMMNH P-31293) are pre-
served. All of the tibiae (e.g. Figs 3E–H) are identical in
morphology and size. The proximal end of the tibia (Fig. 3E)
has a well-developed cnemial crest that curves laterally with
a blunt, squared-off anterior end. This results in the formation
of a distinct, semicircular excavation on the lateral side of
the tibia. All of these features are present in Herrerasaurus
(Novas 1993), Guaibasaurus (our pers. obs.), Saturnalia
(Langer 2003), basal sauropodomorphs (e.g. Galton &
Upchurch 2004), Coelophysis sp. (Padian 1986), Coelophysis
bauri and Allosaurus (Madsen 1976). In Silesaurus and
Eoraptor (our pers. obs.), the cnemial crest does not arch lat-
erally and has a rounded anterior extremity. In Ceratosaurus
and tetanurans the lateral excavation widens so that the lateral
condyle appears triangular in proximal view (Rauhut 2003).
The appressed lateral surface on the tibial shaft described by
Heckert et al. (2000b, 2003) is not present in Coelophysis sp.
(Padian 1986) and Coelophysis bauri and cannot be homo-
logous to a similar feature on Eucoelophysis (see previous
Re-evaluation of North American Late Triassic dinosaur taxa 217
Figure 4 Comparison of the astragalocalcanea of Coelophysis bauri (AMNH FR 30576) (left) in dorsal (A), ventral (B), posterior (C)and
anterior (D) views, with the astragulus of Chindesaurus bryansmalli (PEFO 33982) (right) in dorsal (E), ventral (F), posterior (G)andanterior(H)
views. Abbreviations: ap, ascending process; cn, calcaneum; pb, posterior basin. Scale bars =1cm.
discussion). Among the preserved material, the appressed
lateral surface is the only tibial character that separates the
small Snyder Quarry theropod from Coelophysis.
The distal tibia is quadrangular in distal view (Fig.
3H). This shape is a result of a strong ridge on the pos-
terior side with a slightly concave posterolateral face and
a slightly convex posteromedial face and a developed des-
cending process of the tibia. This overall quadrangular shape
is found in Saturnalia (Langer 2003), basal sauropodo-
morphs (e.g. Galton & Upchurch 2004), Coelophysis sp.
(Padian 1986), Coelophysis bauri and Dilophosaurus.In
Silesaurus (Dzik 2003), Eoraptor (our pers. obs.), Herrera-
saurus and Chindesaurus, the distal tibia is sub-rounded
with little or no descending process. As in Coelophysis sp.
and Coelophysis bauri, the descending posterolateral pro-
cess of the tibia extends laterally well beyond the body
of the tibia, whereas in Saturnalia and basal sauropodo-
morphs it does not. The anterior portion of the body of the
distal tibia is also excavated more dorsally in Coelophysis
and the Snyder Quarry material than in Saturnalia or basal
sauropodomorphs.
A second possible dinosaur identified by Heckert et al.
(2000b, 2003) is represented by a fused tibia and fibula that
is missing the midshaft and fused with a complete astragalo-
calcaneum (Figs 5A–C) (NMMNH P-29268). The tibia bears
a laterally curved and blunt cnemial crest that is similar to
Herrerasaurus,Saturnalia,Coelophysis sp. and Coelophysis
bauri. The fusion of the proximal tibia with the proximal
fibula obscures the identification and morphology of the me-
dial and lateral condyles. For the same reason, the presence
or absence of the appressed tibial surface cannot be determ-
ined. Thus, the fused distal tibia, fibula and astragalocal-
caneum complex cannot be distinguished from that of corres-
ponding fused elements in Coelophysis bauri,Coelophysis
rhodesiensis and Syntarsuskayentakatae. Furthermore,
these taxa and NMMNH P-29268 all share the fusion of
these elements (Rowe & Gauthier 1990; Tykoski & Rowe
2004). Therefore, this bone is assigned to Coelophysoidea
indet.
An isolated ilium (Figs 6E-H) (NMMNH P-35995) as-
signed by Heckert et al. (2000b, 2003) to Eucoelophysis sp.,
although missing much of the iliac blade, shows remarkable
similarities to the holotype ilium of Caseosaurus crosbyensis
(Figs 6A–D: Hunt et al. 1998). Shared characters include a
short, pointed anterior process of the ilium, a strong ridge run-
ning anterodorsally from the acetabular rim to the anterior
preacetabular process, a wide, open angle between the an-
terior process and the pubic process, a moderately developed
supra-acetabular rim and an ischiadic process with a roun-
ded distal end that is dorsal to the distal end of the pubic
process. None of these characters are found in Coelophysis
sp. (Padian 1986), Coelophysis bauri,Coelophysis rhodesi-
ensis (Raath 1969), Syntarsuskayentakatae (Rowe 1989),
or Dilophosaurus. Unfortunately, with only an isolated ilium
known for both NMMNH P-35995 and Caseosaurus,the
affinities of this taxon are unclear. The strong anterodorsal
ridge appears to be present in Saturnalia (Langer 2003) and
Efraasia minor (Galton 1984: plate I, fig. 7; Yates 2003a),
although in Saturnalia this ridge twists medially behind the
preacetabular process of the iliac blade (our pers. obs.). It is
found convergently in Poposaurus and Shuvosaurus (Long
& Murry 1995), but it differs in these taxa in originating on
the lateral extent of the dorsal surface of the supra-acetabular
rim. The acetabulum in NMMNH P-35995 and Caseosaurus
is at least partially perforate, but the broken margin makes
it unclear to what degree it was open. The only iliac char-
acter state that diagnoses the Dinosauria according to Fraser
et al. (2002) is a ‘largely to fully perforate acetabulum.’
218 S. J. Nesbitt et al.
Figure 5 Distal portion of the large coelophysoid (NMMNH P-29168) right (reversed) tibia, fibula and complete astragalocalcaneum in
anterior (A), posterior (B) and ventral (C) views. (Note: the proximal portion is not figured, but it is present in the specimen). Distal portion of the
holotype left tibia, complete astragalus and calcaneum of Camposaurus arizonensis (UCMP 34498) in anterior (D), posterior (E) and ventral (F)
views. Coelophysis bauri (AMNH FR 30614) left, juvenile tibia, fibula and complete astragalocalcaneum in anterior (G), posterior (H) and ventral
(I) views. Coelophysis bauri (AMNH FR 30615) left, adult tibia, fibula and complete astragalocalcaneum in anterior (J), posterior (K) and ventral
(L) views. Line drawing of the relative proportions of the tibia, fibula and astragalocalcaneum in anterior (M), posterior (N) and ventral (O)views
(from Coelophysis bauri J–K). Abbreviations: as, astragalus; cn, calcaneum; ,fibula;ti, tibia. Scale bars =1cm.
Because this is unclear in NMMNH P-35995 and Caseo-
saurus, it cannot be determined whether these specimens
represent dinosaurs.
Several isolated vertebrae from the Snyder Quarry were
also considered theropod by Heckert et al. (2000b, 2003).
The large dorsal vertebrae NMMNH P-33691 is poorly pre-
served and does not possess any dinosaur synapomorph-
ies. Two small dorsal vertebrae (NMMNH P-30779 and
30780) have strongly triangular transverse processes in dorsal
view, a character shared with Coelophysis bauri,Coelophysis
rhodesiensis,‘Syntarsuskayentakatae and other coelophys-
oids (Rowe & Gauthier 1990; Tykoski & Rowe 2004). Thus,
these two specimens probably pertain to the coelophysoid
theropod in the quarry. A single distal caudal vertebra cata-
logued under ‘Theropoda’ (NMMNH P-29996) is identical
to corresponding vertebrae of Coelophysis sp. (Padian 1986),
but cannot be differentiated from other archosaur distal
caudal vertebrae.
In summation, the Snyder Quarry preserves two, pos-
sibly three distinct ornithodirans that are not referable to Eu-
coelophysis. The large remains (NMMNH P-29268) prob-
ably pertain to a coelophysoid; the smaller, better repres-
ented, remains belong to a coelophysoid closely related to
Coelophysis. The presence of an appressed surface on the
lateral side of the tibia in the small Snyder Quarry coelophys-
oid differentiates it from Coelophysis. Unfortunately, most of
the phylogenetically informative character states in this ma-
terial are also present in Dilophosaurus (except those listed
above for the isolated astragalus). If Dilophosaurus is outside
Coelophysoidea (e.g. Carrano et al. 2002; Rauhut 2003), then
these characters only constrain the material to non-tetanuran
theropods. Another ornithodiran from the Snyder Quarry is
represented by a partial ilium (NMMNH P-35995) that may
or may not pertain to a dinosaur and is similar to Caseo-
saurus.
Coelophysis bauri Cope, 1889
AGE.Norian, Late Triassic.
OCCURRENCE.‘Siltstone member,’ Chinle Formation
(Stewart et al. 1972), Rio Arriba County, New Mexico, USA.
NEOTYPE.AMNH FR 7224, almost complete articulated
skeleton.
REFERRED MATERIAL.Numerous specimens from the Ghost
Ranch Coelophysis quarry in the collections of several North
American institutions. See Colbert (1989) for more detail.
TAXONOMIC PLACEMENT.A valid taxon and basal member
of the Neotheropoda.
REMARKS.The tortured nomenclatorial history of Coelo-
physis bauri has been reviewed extensively (Padian 1986;
Sullivan & Lucas 1999). As a result of the ICZN ruling,
the name-bearing type is now a nearly complete skeleton
(AMNH 7224) from the extensive Ghost Ranch assemblage
(Colbert et al. 1992). It is clear that this spectacular as-
semblage of specimens represents a theropod taxon that
is very similar to other Late Triassic and Early Jurassic
coelophysoids. Characters of Coelophysis bauri satisfy all
of the criteria for referral to Dinosauria.
Re-evaluation of North American Late Triassic dinosaur taxa 219
Figure 6 Holotype ilium (UMMP 8870) of Caseosaurus crosbyensis in lateral (A,B) and medial (C,D) views compared to a similar ilium from
the Snyder Quarry (NMMNH P-35995) in lateral (E,F) and medial (G,H) views. Stippling represents breaks and gaps filled with adhesive;
cross-hatching indicates broken surfaces. Abbreviations: ac, acetabulum; ar, acetabular rim; iap, anterior process of the ilium; ip,ischial
peduncle; pp, pubic peduncle; r,rugosity;sa, sacral rib articulation. Scale bars =1cm.
Coelophysis bauri is well supported as a basal mem-
ber of the Neotheropoda in numerous phylogenetic analyses
(Gauthier 1986; Rowe & Gautier 1990; Carrano et al. 2002;
Rauhut 2003). As one of the best known coelophysoids, C.
bauri consistently falls out as one of the most derived mem-
bers of the Coelophysidae (Rauhut 2003; Tykoski & Rowe
2004). Because of its unambiguous position as a dinosaur
and coelophysoid theropod, the reevaluation of Late Trias-
sic dinosaurs presented here uses C. bauri as a reference for
comparison with other ‘dinosaurian’ taxa (Figs 4, 5G–L).
220 S. J. Nesbitt et al.
Coelophysis material of Cope
AGE.Norian, Late Triassic.
OCCURRENCE.?Petrified Forest Member, Chinle Forma-
tion, New Mexico, USA.
MATERIAL.Diagnostic material includes AMNH FR 2706,
pubis; AMNH FR 2705, a right ilium; AMNH FR 2708,
another right ilium; AMNH FR 2722, fused sacral vertebrae.
TAXONOMIC PLACEMENT.The diagnostic portions of Cope’s
original syntype material belong to a coelophysoid similar to
Coelophysis bauri.
REMARKS.Sullivan et al. (1996) and Sullivan & Lucas
(1999) argued that the original Coelophysis material collec-
ted by Baldwin and described by Cope did not come from the
AMNH Coelophysis Quarry as suggested by Colbert (1989).
They hypothesised that the material was from the Petrified
Forest Member rather than the ‘siltstone member’ (Stewart
et al. 1972; Schwartz & Gillette 1994) where the Coelophysis
Quarry lies, and probably from the holotype locality of Eu-
coelophysis baldwini (Sullivan & Lucas 1999). We agree
with Sullivan et al. (1996) and Sullivan & Lucas (1999) that
Baldwin’s original material does not match well with the
preservation of the Coelophysis Quarry material and prob-
ably derives from the Petrified Forest Member of the Chama
Basin. However, Sullivan and colleagues make an uncon-
vincing argument for placement of Baldwin’s Arroyo Seco’
Coelophysis material at the Eucoelophysis locality. Both
the Eucoelophysis locality and the Coelophysis Quarry are
equally remote from Arroyo Seco proper. Furthermore, fos-
siliferous outcrops of the Petrified Forest Member that have
produced dinosaur material are found directly adjacent to Ar-
royo Seco (Downs 2005) and are near the historically main
transportation routes in the valley. These represent more vi-
able possibilities for the locality of Baldwin’s material.
The designation of a neotype specimen of Coelophysis
bauri from the Ghost Ranch Coelophysis Quarry left Cope’s
original syntype material of Coelophysis without a name.
Sullivan & Lucas (1999) referred one specimen (AMNH FR
2706) to Eucoelophysis baldwini but, as discussed above, this
referral cannot be substantiated.
Much of Cope’s original Coelophysis material is well
preserved. In the next section, we discuss some of the more
diagnostic material from the original collection. Because the
original syntypes are assignable to at least two taxa (see
below), we will treat each element as a separate specimen to
prevent future confusion.
Most of the original syntype material consists of limb
fragments, pedal elements and vertebrae. The association of
the material is not clear, but the similar preservation and sim-
ilar coloured matrix around some of the elements suggest
that the material was found in one area, possibly the same
horizon. The limb fragments and pedal elements are undia-
gnostic within Archosauria as isolated elements. Moreover,
AMNH FR 2725, a femur without a fourth trochanter and a
small sulcus on the distal surface precludes an assignment to
Dinosauria. This femur possibly belongs to a Shuvosaurus-
like taxon because of the absence of the fourth trochanter
and indicates that other archosaurs were discovered mixed
together with the original Coelophysis syntype material. The
limb fragments and pedal elements cannot be unambigu-
ously assigned to the Theropoda. The vertebrae suffer from
the same problem. None of the dorsal vertebrae preserve the
neural arches, which are needed to differentiate archosaur
vertebrae. Most of the cervical vertebrae have both anterior
and posterior excavations of the centrum that have been pre-
viously referred to as pleurocoels (Colbert 1989; Rowe &
Gauthier 1990; Rauhut 2003). These cervicals are indistin-
guishable from other coelophysoids.
The pelvic elements can be referred to the Theropoda.
AMNH FR 2705, a right ilium, has non-tetanuran thero-
pod or coelophysoid character states (depending on whether
Dilophosaurus is a coelophysoid or a taxon closer to Teta-
nurae than to coelophysoids) including: a well developed
supra-acetabular rim (or crest) that arcs ventrally at its lateral
margin; a ‘squared-off’ distal portion of the posterior iliac
process; a deep brevis fossa where the lateral ridge origin-
ates near the supra-acetabular rim; flattened dorsal margin
of the iliac blade; and a fully perforated acetabulum. All of
these features are also found in AMNH FR 2708, another
right ilium. A right pubis (AMNH FR 2706), referred by
Sullivan & Lucas (1999) to Eucoelophysis baldwini,hasa
small distally expanded boot that is identical to Coelophysis
bauri. In proximal view, three regions of articulation are
clearly defined: one that articulates with the ilium, one that
indicates that the acetabulum which was at least partially
open and one that articulates with the ischium. Recent repre-
paration of this element reveals the presence of both an obtur-
ator foramen and a pubic foramen, a coelophysoid character
(Rowe & Gauthier 1990; Rauhut 2003; Tykoski & Rowe
2004). An anterior portion of an ilium attached to four fused
sacral vertebrae (AMNH FR 2722) is identical to corres-
ponding elements of Coelophysis bauri and the small Snyder
Quarry coelophysoid. The ilium fragment indicates that the
acetabulum was partially open and that the supra-acetabular
rim was well developed.
Although none of the characters are directly diagnostic
of Coelophysis bauri, there are no contradictory characters
that would separate Cope’s original syntype material from
that of the neotype of Coelophysis bauri (AMNH FR 7224).
In sum, the diagnostic portions of Cope’s original syntype
material belong to a coelophysoid similar to Coelophysis
bauri.
Gojirasaurus quayi Carpenter, 1997
[=Revueltoraptor lucasi’; Hunt 1994; =‘Herrerasaurid A’;
Hunt et al. 1998]
AGE.Norian, Late Triassic.
OCCURRENCE.Bull Canyon Formation (=Cooper Canyon
Formation), Dockum Group, Quay County, New Mexico,
USA (Carpenter 1997).
HOLOTYPE.UCM 47221, partial skeleton.
REFERRED MATERIAL.Hunt (1994) referred the following
isolated postcranial material to this taxon, none of which
is diagnostic. NMMNH P-4666, pubis; NMMNH P-16607,
teeth fragments; NMMNH P-16656, dorsal and caudal
centra; NMMNH P-17258, vertebrae and fragmentary
scapula; NMMNH P-17134, fragments of pelvis and dorsal
and caudal vertebrae; UMMP 7274 (in part), two dorsal
centra.
TAXONOMIC PLACEMENT.Coelophysoidea incertae sedis.
Re-evaluation of North American Late Triassic dinosaur taxa 221
REMARKS.The holotype and only known specimen of Gojir-
asaurus (Parrish & Carpenter 1986: figs 11.5–11.7; Car-
penter 1997: figs 2–8) was collected from the Bull Canyon
(=Cooper Canyon) Formation in Quay County, New Mexico,
from a bone bed containing microvertebrates, aetosaurs,
a phytosaur (Pseudopalatus sp.) and Shuvosaurus sp.
(Parrish & Carpenter 1986; Carpenter 1997). From this mixed
assemblage of disarticulated bones, a tooth, four dorsal ver-
tebrae, a scapula, a pubis, ribs, a chevron and a complete tibia
were assigned to the holotype of Gojirasaurus (Carpenter
1997). Hunt et al. (1998) referred to this taxon as ‘Herrera-
saurid A’ and referred several NMMNH specimens from the
Bull Canyon Formation of New Mexico to this taxon. In his
dissertation, Hunt (1994) named UCM 47221 Revueltorap-
tor lucasi and referred numerous NMMNH specimens to it.
None of the specimens (listed above) from the Bull Canyon
Formation referred to this taxon can be distinguished from
those of Shuvosaurus or other archosaurs and, therefore, can-
not be referred to Gojirasaurus. Hunt (1994) referred UCM
47221 to the Herrerasauridae based on the strap-like scapu-
lar blade, an elongate pubis and shortened posterior dorsal
vertebrae.
Because the holotype of Gojirasaurus is from a mixed,
disarticulated assemblage (Parrish & Carpenter 1986), the
association of the fossil material remains problematic. The
tibia and pubis of the holotype of Gojirasaurus belong to a
coelophysoid theropod, whereas some of the included ma-
terial cannot be differentiated from the contemporaneous
Shuvosaurus-like taxon and most of the remaining mater-
ial is non-diagnostic. The tooth was found isolated and spent
tooth crowns are common in fossil quarries and cannot be
assigned by proximity to a certain taxon in a mixed as-
semblage. Moreover, mediolaterally compressed, serrated
teeth are present in a variety of archosaurs (e.g. ‘rauisuchi-
ans’) that lived contemporaneously with theropod dinosaurs
(e.g. Long & Murry 1995).
The four centra and one neural arch cannot be clearly
assigned to the Dinosauria and are not diagnostic to a more
specific clade within Archosauria. Rauhut (2003) scored the
vertebrae of Gojirasaurus into his basal theropod matrix,
but none of the character states scored for the vertebrae
of Gojirasaurus were unambiguous synapomorphies of any
theropod clade. In addition, the vertebrae assigned to Gojir-
asaurus cannot be differentiated from the vertebrae of the
suchian archosaur Shuvosaurus. The vertebrae of Shuvo-
saurus have a deep lateral fossa on the centrum, coarse ridges
along the centrum face rims and the diapophysis and parapo-
physis are both on the transverse process, features also found
in dinosaurian vertebrae. Even though many of the neural
spines of the dorsal vertebrae of Shuvosaurus are low, the
posterior dorsal neural spines are taller and comparable to
those assigned to Gojirasaurus. Carpenter (1997) described
hyposphene–hypantrum articulations on the single neural
arch of a posterior dorsal vertebra of Gojirasaurus.How-
ever, the dorsal vertebrae of Shuvosaurus and other suchians
(e.g. Batrachotomus,Arizonasaurus and Desmatosuchus)
also have hyposphene–hypantrum articulations between the
vertebrae. Therefore this character is not exclusive to dino-
saurs.
In addition, Parrish & Carpenter (1986) described an
edentulous premaxilla (UCM 52081) from the same quarry
that is identical to the premaxilla of Shuvosaurus (Hunt
1994). New specimens from the Ghost Ranch Coelophysis
Quarry (Nesbitt & Norell 2006) indicate that the skull of
Shuvosaurus belongs to the postcranial skeleton of Chatter-
jeea (see full discussion below) as postulated by Long &
Murry (1995). The size of the premaxilla suggests that the
vertebrae of the animal would be smaller than those assigned
to Gojirasaurus, but it is possible that a larger Shuvosaurus-
like taxon would have vertebrae identical to those assigned
to Gojirasaurus. Therefore, the dorsal vertebrae cannot be
confidently assigned to a theropod. The ribs, gastralia and
chevron are not diagnostic and also cannot be assigned to the
Theropoda,let alone clades within Archosauria.
The scapula, represented by a nearly complete element,
cannot be assigned directly to the Theropoda or Dinosauria,
although it is not inconsistent with such an assignment. The
scapula of Gojirasaurus shares no apomorphies with thero-
pods such as Coelophysis bauri,‘Syntarsuskayentakatae
and Coelophysis rhodesiensis. Although coelophysoids have
an expanded distal margin of the scapula as found in Gojir-
asaurus, this feature is also found in a variety of other Tri-
assic archosaurs such as stagonolepidids and taxa such as
Postosuchus (Chatterjee 1985). Carpenter (1997) assigned
a pubis with a pubic fenestra to Gojirasaurus that was
later used by Rauhut (2003) to infer a close relationship
to Coelophysis bauri and other coelophysoids. The presence
of a pubic fenestra is not completely clear as most of the area
is broken around the pubic fenestra; however, a small region
of finished bone suggests that a pubic fenestra was present
and, hence, it indicates that at least the pubis belongs to a
coelophysoid (Rauhut 2003). The other character states of
the pubis scored by Rauhut (2003) are symplesiomorphies
within the Theropoda and probably Archosauria. The size of
the pubis and scapula suggest that they belong to the same
animal as the tibia, yet we are hesitant to assign all the bones
to one taxon in the absence of unambiguous synapomorph-
ies and the presence of other non-dinosaur archosaurs in the
holotype quarry.
The tibia can be assigned to the Dinosauriformes based
on the presence of a cnemial crest, two proximal posterior
condyles and a well-developed slot at the distal end of the
tibia that accepts the ascending process of the astragalus. All
of these characters are present in Silesaurus, a non-dinosaur
dinosauriform (Dzik 2003), and Marasuchus (Sereno & Ar-
cucci 1994). The laterally-curved blunt cnemial crest is found
in Saturnalia, basal sauropodomorphs, Coelophysis bauri
and other theropods. The distal end is subrectangular with a
small posterolateral process in distal view. Rauhut (2003:
character 208) used this character to unite Gojirasaurus,
Dilophosaurus,Coelophysis bauri,Coelophysis rhodesien-
sis and Liliensternus. A subrectangular distal end of the
tibia is also found in basal sauropodomorphs such as Plateo-
saurus (Galton & Upchurch 2004) and Riojasaurus (R.B.I.,
pers. obs.); however, the Gojirasaurus tibia shares with
Coelophysis bauri,Coelophysis sp., Coelophysis rhodesi-
ensis,‘Syntarsuskayentakatae,Liliensternus liliensterni,
Dilophosaurus and the Snyder Quarry small coelophysoid
taxon a posterolateral process of the tibia that extends lat-
erally well beyond the body of the tibia, and the anterior
portion of the body of the distal tibia is also excavated
more dorsally than in basal sauropodomorphs such as Rioja-
saurus. Tetanuran theropods and some neoceratosaurs lose
the subrectangular shape in distal view (Rauhut 2003), so
the Gojirasaurus tibia can be identified as a non-tetanuran
theropod.
222 S. J. Nesbitt et al.
Our analysis indicates that the holotype of Gojirasaurus
may include several taxa. Part of the holotype material,
the tibia in combination with the pubis, can be assigned
to a coelophysoid theropod. The only character that sep-
arates Gojirasaurus from Coelophysis is the robustness of
the tibia; however, the Coelophysis specimen described by
Padian (1986), although smaller, has very similar tibial pro-
portions. Therefore, it is entirely possible, though not cer-
tain, that the material Padian (1986) described and Gojir-
asaurus belong to the same taxon. Because Gojirasaurus
has no autapomorphies or a unique combination of character
states, we consider it a metataxon, following Rauhut (2003),
and Coelophysoidea incertae sedis. Furthermore, we restrict
only the diagnostic material to the holotype, the tibia and
pubis.
Bluewater Creek Member ‘theropod’ material
[=Cinizasaurus hunti Heckert 1997; =‘Theropoda, prob-
able new genus and species’ Heckert 1997; =Theropoda in-
det. Heckert et al. 2000a]
AGE.?Late Carnian, Late Triassic.
OCCURRENCE.Bluewater Creek (=Mesa Redondo) Mem-
ber of the Chinle Formation near Fort Wingate, New Mexico,
USA.
MATERIAL.NMMNH P-18400, vertebrae, tibia, fragments;
NMMNH P-18401, dorsal vertebrae.
TAXONOMIC PLACEMENT.Archosauriformes indet.
REMARKS.Heckert (1997) considered NMMNH P-18400
a distinct theropod, but later considered it ‘not generic-
ally determinate’ (Heckert et al. 2000a). There are no de-
rived character states that it shares with theropods such as
Coelophysis bauri,Coelophysis sp., Coelophysis rhodesien-
sis,orDilophosaurus. The vertebrae cannot be differentiated
from other basal archosaurs. The proximal tibia does not have
a differentiated cnemial crest or lateral and medial condyles.
The rest of the limb elements cannot be differentiated from
those of other basal archosaurs.
Heckert et al. (2000a) concluded that NMMNH P-
18401 represented a distinct theropod with ‘highly derived’
dorsal centra that had a ventral keel. The centra have no char-
acteristics they share with Coelophysis and other theropods to
the exclusion of all other archosaurs. Furthermore, a ventral
keel on dorsal vertebrae is found in Postosuchus (Long &
Murry 1995) and basal crocodylomorphs such as Hes-
perosuchus (Parrish 1991). Therefore, a ventral keel is not
unique to theropods. Accordingly, both of these specimens
should be considered Archosauriformes indet.
Santa Rosa Formation ‘theropod’ material
AGE.?Late Carnian, Late Triassic.
OCCURRENCE.Los Esteros Member of the Santa Rosa
Formation, Dockum Group, New Mexico.
MATERIAL.NMMNH P-13006, two fused sacral centra;
NMMNH P-25749, fragmentary ‘femur’ and pubis; and
NMMNH P-25750, metatarsals.
TAXONOMIC PLACEMENT.Archosauria indet.
REMARKS.Heckert et al. (2000a) considered this mater-
ial to belong to theropods, most probably coelophysoids.
NMMNH P-13006 consists of two fused sacral centra that
Heckert et al. (2000a) referred to the Theropoda on the basis
of being hollow. Hollow centra are also found in crocodylo-
morphs and Shuvosaurus, so this specimen should be con-
sidered Archosauria indet. The femur of NMMNH P-25749
may not be a femur because it is eroded and typical distin-
guishing features of the femur are not present. The proximal
end of the pubis of this specimen has an obturator fora-
men, but this is plesiomorphic for Archosauria. There is no
evidence for an acetabular rim on the proximal pubis that
is present in dinosaurs with an open acetabulum. Therefore,
NMMNH P-25749 cannot unambiguously be considered a
dinosaur. Heckert et al. (2000a) compare NMMNH P-25750
to the metatarsals of Eucoelophysis, but because these ele-
ments cannot be differentiated from other archosaurs, neither
specimen can be considered a theropod or dinosaur.
Arizona
Coelophysis sp. (Padian, 1986)
AGE.Norian, Late Triassic.
OCCURRENCE.Petrified Forest Member, Chinle Formation,
Petrified Forest National Park, Arizona, USA.
MATERIAL.UCMP 129618, most of the pelvis and hindlimb,
posterior dorsal vertebrae and caudal vertebrae; PEFO 33981,
fragmentary skeleton with parts of the posterior vertebral
column, pelvis and most of the hindlimbs; PEFO 33983, most
of the posterior portion of the skeleton, under preparation.
All of these specimens represent a coelophysoid of the same
size and with a similar morphology.
TAXONOMIC PLACEMENT.Coelophysis sp.
REMARKS.Padian (1986) described a partial skeleton of
Coelophysis from the Petrified Forest Member of the
Chinle Formation of Petrified Forest National Park, Arizona.
Whereas he recognised many similarities with Coelophysis
bauri from Ghost Ranch, he also noted some small differ-
ences, especially in the robustness of the hindlimb. Recent
recovery of new specimens of the same taxon from equival-
ent strata in Petrified Forest National Park suggests that the
Petrified Forest taxon is generally larger and more robust than
the Ghost Ranch material. We recognise that these are not
features that can be used alone to distinguish separate taxa,
but combined with the lengthy temporal gap between the
Petrified Forest and Ghost Ranch specimens, we refrain from
referring the Petrified Forest material to C.bauri pending ad-
ditional preparation and detailed study.
Hunt (1998) attributed a proximal portion of a tibia
(NMMNH unnumbered) from the Blue Mesa Member near
Blue Mesa inside the Petrified Forest National Park to a
theropod about the same size as the Coelophysis specimen
described by Padian (1986). The proximal portion of the tibia
bears a cnemial crest and two divided posterior condyles.
These features are not diagnostic to Theropoda; thus, this
specimen cannot be assigned to the Theropoda.
‘Camposaurus arizonensis’ Hunt et al., 1998 (Fig. 5)
AGE.Late Carnian, Late Triassic.
Re-evaluation of North American Late Triassic dinosaur taxa 223
OCCURRENCE.Mesa Redondo Member, Chinle Formation
(Lucas et al. 1997; Heckert & Lucas 2003), Apache County,
Arizona, USA.
HOLOTYPE.UCMP 34498, fused tibiae, fibulae and astraga-
localcanea of the right and left sides.
REFERRED MATERIAL.Hunt et al. (1998) referred additional
material (e.g. MNA V3091) to this taxon; however, see dis-
cussion below.
TAXONOMIC PLACEMENT.Coelophysoidea indet.
REMARKS.Long & Murry (1995) referred several isolated
elements from the Placerias Quarry to Ceratosauria indet.
Hunt et al. (1998) considered all of this material to represent
a single theropod taxon, perhaps even a single individual.
They concluded that this taxon was distinct from other Tri-
assic theropods and designated matching right and left fused
distal tibiae, fibulae and astragalocalcanea (Figs 5D–F) as the
holotype of a new taxon, ‘Camposaurus arizonensis,’ with
the other Placerias Quarry ‘theropod’ material as paratypes.
Because all the material is disarticulated and disassociated in
the quarry, the referred material will be considered separately
below.
Hunt et al. (1998) distinguished Camposaurus from
Coelophysis bauri and Syntarsus (it is unclear whether they
compared it to Coelophysis rhodesiensis,‘Syntarsuskayen-
takatae, or both) in having a ventral margin of the astragalus
that is horizontal rather than concave in anterior and posterior
view. We could not corroborate this difference when directly
comparing Camposaurus’toCoelophysis bauri (AMNH
FR 30614 and AMNH FR 30615) material. One difference
between Camposaurus,’ some specimens of Coelophysis
bauri and all other theropods is that in ventral view, the
concave depression on the anterior side of the astragalus is
much stronger and more abrupt in Coelophysis bauri;how-
ever, some specimens of Coelophysis bauri have a morpho-
logy identical to Camposaurus’. This is illustrated in Fig. 5,
which shows that the range of variation between juvenile and
adult Coelophysis bauri is comparable to the small differ-
ence between the ankle regions of most Coelophysis bauri
specimens and Camposaurus’. Therefore, we refer Cam-
posaurus to Coelophysoidea indet. and consider it a nomen
dubium following Downs (2000), Heckert (2001) and Rauhut
(2003).
Other Placerias Quarry material
Additional isolated material was assigned to Ceratosauria in-
det. by Long & Murry (1995) and referred to Camposaurus
by Hunt et al. (1998). None of these assignments can be
substantiated. The femur figured by Long & Murry (1995:
figs 191, 192A–E), UCMP 139622, is badly weathered, but
has an offset proximal head, an apparent ventral sulcus
on the femoral head, a moderately developed trochanteric
shelf of the anterior trochanter and a facies articularis an-
titrochanterica. Therefore, we refer it to Saurischia indet.
None of the dorsal vertebrae figured by Long & Murry
(1995: fig. 192) (UCMP 177317, MNA V3091 [incorrectly
listed as V2777 in Long & Murry 1995: fig. 192]) are dia-
gnostic they are equally comparable to many dinosaur-
iforms as well as Shuvosaurus. The same is true for the
sacral vertebrae (UCMP 138591, 178047, 178048, 178049)
figured and listed by Long & Murry (1995: fig. 192Y;
pp. 189, 238). The distal left tibia (UCMP 25793) that
Long & Murry (1995) refer to ‘?Prosauropoda indet.’
is not quadrangular in ventral view as present in Sat-
urnalia (Langer 2003), other basal sauropodomorphs (e.g.
Galton & Upchurch 2004) and Coelophysis bauri,butis
very similar to Silesaurus (Dzik 2003), Eoraptor (R.B.I.
pers. obs.) and Herrerasaurus (Novas 1993) in possess-
ing a posterolateral process of the distal tibia that has an
unexpanded distal tibial margin that is convex in distal
view. Therefore, we refer UCMP 25793 to Dinosauriformes
indet.
An unpublished distal femur from the Placerias Quarry
(UCMP 25834), although similar to a Shuvosaurus-like taxon
distal femora, is referable to Dinosauriformes indet. on the
basis of a fibular groove that opens at an obtuse angle and
a rounded fibular condyle (Parker & Irmis 2005). This is
identical to the distal femur morphologies of Silesaurus (Dzik
2003), Herrerasaurus (Novas 1993) basal sauropodomorphs
and coelophysoids. A second unpublished specimen from the
Placerias Quarry (UCMP 25820) is a distal tibia. Although
broken, it has a well-developed descending posterolateral
process, a concave posterolateral margin in distal view and a
well developed dorsal excavation for insertion of the ascend-
ing process of the astragalus. These features, in combination
with a posterolateral process that extends well beyond the
body of the tibia laterally, allow us to refer this specimen
to Theropoda indet. It is possible that these two elements
belong to Camposaurus.’
Texas
Protoavis texensis Chatterjee, 1991
AGE.Norian, Late Triassic.
OCCURRENCE.Tecovas and Bull Canyon (=Cooper
Canyon) Formations, Garza County, Texas, USA.
HOLOTYPE.TTUP 9200, partial skull and postcranial mater-
ial of a large individual from the Post Quarry (Bull Canyon
Formation).
REFERRED SPECIMENS.TTUP 9201, partial skull and skel-
eton of a small individual from the Post Quarry (Bull Canyon
Formation); TTUP 9350–9380, various isolated elements
from the Kirkpatrick Quarry (Tecovas Formation) (Chatter-
jee 1999). Many authors (Ostrom 1987, 1991, 1996; Chiappe
1995, 1998; Padian & Chiappe 1998; Witmer 2001, 2002)
believe the associated specimens do not belong to a single
individual.
TAXONOMIC PLACEMENT.Non-tetanuran theropod in part.
REMARKS.Protoavis Chatterjee,1991 is a problematic taxon
that has been heavily discussed in the last decade because of
its possible importance in understanding the origin and evol-
ution of birds. Many skeletal elements and partial elements
of Protoavis were collected from above the Post (Miller)
Quarry in the 1980s and other specimens referred to Pro-
toavis were collected from the underlying Tecovas Forma-
tion. The bones have been completely freed of matrix, some
are heavily reconstructed and the identification of some of the
elements have been questioned (Ostrom 1987, 1991, 1996;
Chiappe 1995, 1998; Witmer 2001, 2002).
224 S. J. Nesbitt et al.
Most authors (e.g. Chiappe 1998; Padian & Chiappe
1998) consider Protoavis