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The anatomy and phylogenetic relationships of the Upper Triassic theropod Zupaysaurus rougieri are reviewed. This taxon is represented by a nearly complete skull and fragmentary postcranial remains recovered from the Los Colorados Formation (Norian), NW Argentina. Originally, Zupaysaurus rougieri was considered a basal member of the Tetanurae, but its anatomy closely resembles that of the Coelophysoidea, supporting its nesting within this theropodan subclade. Thus reinterpreted, Zupaysaurus represents the first record of coelophysoids in South America. Phylogenetic analyses perfomed in this study depict Zupaysaurus as a non-coelophysid coelophysoid. Autopomorphic traits of Zupaysaurus include: maxillary-jugal ventral margin forming an obtuse angle in lateral view, tibia with a very deep and caudally open caudal fossa for the reception of an astragalar caudal process. Within the phylogenetic context outlined here, the derived features shared with Tetanurae (e.g. maxillary fenestra, caudally forked ascending ramus of the maxilla) are better interpreted as homoplasies rather than tetanuran derived features.
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Phylogenetic relationships of the Triassic theropod
Zupaysaurus rougieri
from NW Argentina
Martin D. Ezcurra
a
; Fernando E. Novas
b
a
Laboratorio de Anatomia Comparada y Evolución de Vertebrados, Museo Argentino de Ciencias
Naturales “Bernardino Rivadavia”, Buenos Aires, Argentina
b
CONICET, Buenos Aires, Argentina
To cite this Article Ezcurra, Martin D. and Novas, Fernando E.(2007) 'Phylogenetic relationships of the Triassic theropod
Zupaysaurus rougieri
from NW Argentina', Historical Biology, 19: 1, 35 — 72
To link to this Article: DOI: 10.1080/08912960600845791
URL: http://dx.doi.org/10.1080/08912960600845791
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Phylogenetic relationships of the Triassic theropod Zupaysaurus
rougieri from NW Argentina
MARTIN D. EZCURRA
1
& FERNANDO E. NOVAS
1,2,†
1
Laboratorio de Anatomia Comparada y Evolucio
´
n de Vertebrados, Museo Argentino de Ciencias Naturales “Bernardino
Rivadavia”, Av. Angel Gallardo 470, Buenos Aires (1405), Argentina, and
2
CONICET, Av. Angel Gallardo 470,
Buenos Aires (1405), Argentina
Abstract
The anatomy and phylogenetic relationships of the Upper Triassic theropod Zupaysaurus rougieri are reviewed. This taxon is
represented by a nearly complete skull and fragmentary postcranial remains recovered from the Los Colorados Formation
(Norian), NW Argentina. Originally, Zupaysaurus rougieri was considered a basal member of the Tetanurae, but its anatomy
closely resembles that of the Coelophysoidea, supporting its nesting within this theropodan subclade. Thus reinterpreted,
Zupaysaurus represents the first record of coelophysoids in South America. Phylogenetic analyses perfomed in this study
depict Zupaysaurus as a non-coelophysid coelophysoid. Autopomorphic traits of Zupaysaurus include: maxillary-jugal ventral
margin forming an obtuse angle in lateral view, tibia with a very deep and caudally open caudal fossa for the reception of an
astragalar caudal process. Within the phylogenetic context outlined here, the derived features shared with Tetanurae (e.g.
maxillary fenestra, caudally forked ascending ramus of the maxilla) are better interpreted as homoplasies rather than tetanuran
derived features.
Keywords: Phylogeny, Basal Theropoda, Coelophysoidea, Late Triassic, Argentina
Introduction
The knowledge of the Late Triassic theropods from
South America has been recently enlarged with the
description of Zupaysaurus rougieri by Arcucci and
Coria (2003). This taxon comes from the Los
Colorados Formation (Late Triassic, La Rioja
Province, NW Argentina) and is represented by an
almost complete skull and several postcranial remains,
including centra of dorsal and caudal vertebrae,
partial scapulocoracoid, some manual unguals, distal
ends of femur, tibia, and fibula, and fused tarsals.
Zupaysaurus fills an important morphological gap in
our knowledge of the early evolution of Neother-
opoda, also representing the first Triassic neotheropod
taxon from South America.
Originally, Arcucci and Coria (1997) interpreted the
specimen as “a theropod more derived than Coelo-
physis”. Later, the same authors (1998) considered this
animal as a ceratosaurian more closely related to
derived neoceratosaurians (e.g. Carnotaurus) than to
Coelophysoidea. However, this view was radically
changed in the most complete and more recent study
of Zupaysaurus offered by Arcucci and Coria (2003),
who concluded that this dinosaur represents the oldest
known member of Tetanurae. This interpretation was
based on the following characters that Zupaysaurus
purportedly shares with Tetanurae: presence of a
maxillary fenestra within the antorbital fossa, maxil-
lary tooth row rostral to the orbit, lacrimal recess
pneumatizated, and tibia with a caudolaterally concave
and transversely expanded distal end. Within the
phylogenetic hypothesis defended by Arcucci and
Coria (2003), the features that Zupaysaurus shares
with Coelophysoidea (and lesser inclusive groups
within this clade) are interepreted as homoplasies or
plesiomorphies of Neotheropoda retained by Zupay-
saurus (e.g. maxilla with alveolar ridge, subnarial gap,
large antorbital fenestra, and astragalus and calca-
neum fused to each other).
However, several derived features warrants
the allocation of Zupaysaurus rougieri within the
ISSN 0891-2963 print/ISSN 1029-2381 online q 2007 Taylor & Francis
DOI: 10.1080/08912960600845791
Correspondence: M. D. Ezcurra, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Av. Angel Gallardo 470, Buenos Aires
(1405), Argentina. E-mail: martindezcurra@yahoo.com.ar
E-mail: fernovas@yahoo.com.ar.
Historical Biology, 2007; 19(1): 35–72
Downloaded By: [Ezcurra, Martín Daniel] At: 16:18 23 February 2011
Coelophysoidea, as recently prompted by other authors
(Carrano and Sampson 2004; Ezcurra and Novas 2005;
Tykoski 2005; Carrano et al. 2005). The main purpose
of the present paper is to discuss the information
available in support of this view, as well as to enlarge the
anatomical data of this Triassic dinosaur.
Institutional abbreviations
AMNH, American Museum of Natural History, New
York; CM, Carnegie Museum, Pittsburgh, Pennsyl-
vania; HMN MB, Humboldt Museum fu
¨
r Natur-
kunde, Berlin; MACN, Museo Argentino de Ciencias
Naturales “B. Rivadavia”, Buenos Aires; MCZ,
Museum of Comparative Zoology, Cambridge;
OUM, Oxford University Museum, Oxford; PULR,
Paleontologı
´
a, Universidad Nacional de La Rioja, La
Rioja; PVL, Paleontologı
´
a de Vertebrados, Fundacio
´
n
“Miguel Lillo”, San Miguel de Tucuma
´
n; PVSJ,
Museo de Ciencias Naturales, Universidad Nacional
de San Juan, San Juan; QG, National Museum of
Natural History, Harare, Rhodesia; UCMP, Univer-
sity of California Museum of Paleontology, California;
USNM, United States National Museum, Washing-
ton DC; YPM, Yale Peabody Museum, New Haven,
Connecticut.
Studied specimens
The following specimens have been used for this
study: Herrerasaurus ischigualastensis (PVL 2566),
Dilophosaurus wetherilli (MACN 18686), Liliensternus
liliensterni (HMN MB R. 2175), Coelophysis bauri
(AMNH 7223, 7224, CM C-3-82, MCZ 4779,
UCMP 129618), Coelophysis rhodesiensis (QG 1),
Zupaysaurus rougieri (PULR 076); Ceratosaurus nasi-
cornis (USNM 4735), Carnotaurus sastrei (MACN-
CH 894), Eustreptospondylus oxoniensis (OUM J
13558), and Allosaurus fragilis (AMNH 5767).
Systematic nomenclature
We accept Rauhut’s (2003) hypothesis of a paraphyletic
Ceratosauria, i.e.: (Coelophysoidea þ (Tetanurae þ
Ceratosauria ( ¼ Neoceratosauria))). The term Aver-
ostra was coined by Paul (2002:05) in order to “include
ceratosaurs, megalosaurs, and abelisaurs”. These
groups include both Ceratosauria þ Tetanurae (sensu
Rauhut 2003:node 11) and Averostra is employed here
to refer to the Ceratosauria þ Tetanurae clade.
Regarding Coelophysoidea systematics, we follow
the definition proposed by Padian et al. (1999) as a
stem based node that enclose all theropods closer to
Coelophysis than to Ceratosaurus. The phylogenetic
analyses here performed support the inclusion of
Dilophosaurus within the Coelophysoidea, as the first
researches of basal neotheropodian systematics (Rowe
1989; Rowe and Gauthier 1990; Holtz 1994, 2000;
Tykoski 1998; Sereno 1999) and more recent authors
have suggested (Tykoski and Rowe 2004; Tykoski
2005; Carrano et al. 2005). Holtz (1994) defined
Coelophysidae as a node based taxon that encloses
Coelophysis, Syntarsus, and all descendants from their
most recent common ancestor.
Our phylogenetic analyses reveal that the African
taxon Coelophysis rhodesiensis ( ¼ Syntarsus rhodesien-
sis) is more closely related to Coelophysis bauri than to
Syntarsus kayentakatae, and several anatomical fea-
tures distinguishes both Coelophysis species from
Syntarsus kayentakatae. Paul (1988, 1993) had
previously indicated that Syntarsus (“S”. rhodesiensis)
was a synonym of Coelophysis (C. bauri), and this
interpretation is here followed.
Anatomical terminology
In the present contribution we follow the directional
terminology used in the Nomina Anatomica Avium
(Clark 1993). Regarding to the cranial anatomy of the
pneumatized antorbital region, we accept the nomen-
clature employed by Witmer (1997).
Systematic paleontology
Dinosauria Owen 1842
Theropoda Marsh 1881
Neotheropoda Bakker 1986
Coelophysoidea Nopcsa 1928
Genus Zupaysaurus Arcucci and Coria 2003
Type species
Zupaysaurus rougieri Arcucci and Coria 2003.
Stratigraphic distribution
Upper levels of the Los Colorados Formation, Agua
de la Pen
˜
a Group, Norian (Caselli et al. 2001).
Geographic distribution
Quebrada de los Jachaleros, 7 km West of National
Route 126, La Rioja Province, NW Argentina.
Holotype
The holotype specimen (PULR 076) of Zupaysaurus
rougieri includes: skull and jaws (lacking both
premaxillae), several vertebrae (atlas, axis, some
postaxial cervicals, dorsals, sacrals, and distal cau-
dals), left scapulocoracoid (lacking scapular blade),
isolated manual unguals, distal ends of both femora,
proximal end of left tibia, distal right tibia and fibula,
and right astragalocalcaneum (see below).
M. D. Ezcurra & F. E. Novas36
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Zupaysaurus rougieri Arcucci and Coria 2003
(Figures 16, 8, 9C,D, 10, 11A,D,G, 13, 14B)
Emended diagnosis
Arcucci and Coria (2003) had diagnosed Zupaysaurus
rougieri on the basis of the following features: 1) oval
and rostroventrally oriented antorbital fenestra, 2) two
parasagital crests on the snout formed by the nasals, 3)
rostral process of lacrimal longer than ventral, 4) main
body of the maxilla with parallel dorsal and ventral
borders, 5) tibial-astragalar articulation locked med-
iocaudally by astragalar process in caudally open tibial
notch. Characters 1, 4, and 5 are used in the present
emended diagnosis, but 1 and 5 have been modified.
On the other hand, character 2 is here considered as a
postmortem artifact (see below), and character 3 is a
synapomorphic feature that diagnoses Coelophysoi-
dea as a whole (Tykoski and Rowe 2004). In the
context of the present review, we interpret Zupay-
saurus as a coelophysoid theropod with the following
autapomorphies: 1) maxillary-jugal ventral margin
describing an obtuse angle in lateral view; 2)
horizontal ramus of the maxilla with parallel dorsal
and ventral margins; 3) notch on the dorsal margin of
the ascending process of the maxilla; 4) cnemial crest
poorly developed; and 5) tibia with a very deep and
caudally open notch for the reception of an astragalar
caudal process. Furthermore, Zupaysaurus differs
from other coelophysoids in the convergent acqui-
sition of the following characters present in some
tetanuran taxa: lacrimal with highly pneumatized
antorbital recess (probably, this feature could con-
stitute the plesiomorphic condition of the Neother-
opoda, see below); horizontal ramus of lacrimal
rostrally tapering onto the forked caudal tip of the
ascending process of the maxilla; and short and
square-shaped retroarticular process of the mandible.
Redescription of Zupaysaurus rougieri
Arcucci and Coria (2003) offered a detailed descrip-
tion of the skull of Zupaysaurus. However, several
postcranial bones of the holotype specimen and
associated materials were only briefly described.
With the aim of improving the anatomical knowledge
on Zupaysaurus rougieri,weofferbelowsome
observations on its cranial morphology and a
redescription of both the postcranial elements of the
holotype specimen and the associated materials.
Elements of the holotype specimen
The holotype of Zupaysaurus rougieri includes skull
and jaws, several vertebrae (atlas, axis, some postaxial
cervicals, dorsals, sacrals, and distal caudals), isolated
manual unguals, distal tibia and fibula, and astraga-
localcaneum. We present below some comments on
the cranial anatomy, regarding the nasal bones, and a
description of some postcranial bones that exhibit
phylogenetically important characters for a reconsi-
deration of the relationships of Zupaysaurus.
Skull
The nasal is a flat bone, slightly grooved on its dorsal
face, with a caudal width of 5 cm approximately
(Figure 1). The left lacrimal and nasal are displaced
and disarticulated from the rest of the skull. The right
nasal is rotated, its dorsal surface facing left, giving the
appearence that a longitudinal crest was present
(Arcucci and Coria 2003). If the nasal pair is placed in
its original position, the curved margins, that produce
a ventral concavity, articulate with the convex margins
of the maxillae. Due to this rotation the nasals crossed
in the rostral extreme of the skull, where the rostral
end of the left nasal cross the right external naris.
Given the erroneous description of parasagital crests
in Zupaysaurus, and the similarity of the postmortem
deformation in the skulls of the Los Colorados taxon
and Syntarsus kayentakatae, a revision of the para-
sagital crests described for the later taxon might be
necessary (Rowe 1989; Tykoski 1998). This structure
might also be a deformation, which was wrongly
interpreted as a pair of parasagital crests on the skull
roof. Furthermore, the lateral margins of the nasals of
Zupaysaurus extend slightly above the maxillae to form
low, longitudinal, and slightly laterodorsally orien-
tated crest on the skull roof; as occurs in Coelophysis
rhodesiensis, Coelophysis bauri, Allosaurus, and sinrap-
torids (Rauhut 2003).
Axial elements
Atlas-axis com plex. The atlas-axis complex is
poorly preserved (Figure 1). As was mentioned by
Arcucci and Coria (2003), the most salient feature of
these axial elements is a blade-like and craniocaudally
extended axial neural spine. This feature is widely
present among basal dinosauromorphs (e.g. Sile-
saurus) as well as in basal theropods (e.g. Coelophysis,
Dilophosaurus, Carnotaurus). Zupaysaurus retained the
plesiomorphic condition. In contrast, the axis of some
ceratosaurians (e.g. Ceratosaurus) and tetanuran
theropods (e.g. Sinraptor, Allosaurus;Currieand
Zhao 1993) exhibt a rod-like neural spine that does
not extended cranially beyond the prezygapophyses.
Although, the axial neural spine of Herrerasaurus does
not extend beyond the prezygapophyses, it is blade
like, resembling the primitive condition present in
basal dinosauriforms and basal theropods.
Forelimb
Manual unguals. Proximal ends of two ungual
phalanges are available (Figure 2). They were
considered as pedal unguals by Arcucci and Coria
(2003), but due to the strong transverse compression
Phylogenetic relationships of Zupaysaurus 37
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Figure 1. Zupaysaurus rougieri skull. (A), (C) right lateral and (B), (D) left lateral views. Abbreviations: alc, alveolar crest; aof, antorbital
fenestra; ax, axis; fs, fossa; ft, fang-like tooth; imf, internal mandibular fenestra; itf, infratemporal fenestra; ln, left nasal; of, orbital fenestra;
pmf, premaxillary foramina; rmp, rostromedial process; rn, right nasal; qf, quadrate foramen.
M. D. Ezcurra & F. E. Novas38
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as well as the presence of a prominent exor
tuberosity, these elements are better interpreted as
manual unguals. They are proportionally diminute in
comparison with the skull length, as is the case in
Coelophysis rhodesiensis (QG 1).
Hindlimb
Tibia and fibula. The distal ends of right tibia
and fibula are preserved in articulation with the
astragalocalcaneum. The distal tibia (Figure 3) is
transversely expanded, mainly due to the lateral
development of the outer malleolus, which slightly
overlaps the distal end of the fibula caudally. The latter
condition differs from that of Tetanurae in which the
outer malleolus almost completely overlaps the distal
end of fibula caudally. In Zupaysaurus the external edge
of the lateral malleolus is polygonal-shaped in cranial
view (Figure 11A), a morphology that is present in
other coelophysoids (i.e. Liliensternus liliensterni,
Gojirasaurus, Coelophysis). In contrast, the outer
malleolus of the distal tibia in Herrerasauridae,
Figure 2. Zupaysaurus rougieri manual ungual. (A) medial, (B) caudal, (C) ventral, and (D) dorsal views.
Figure 3. Zupaysaurus rougieri distal right tibia. (A) cranial, (B) lateral, (C) caudal, (D) medial, and (E) distal views. Abbreviations: clf,
craniolateral facet; lm, lateral maleoulus; mm, medial maleoulus; tn, tibial notch.
Phylogenetic relationships of Zupaysaurus 39
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Dilophosaurus, Ceratosauria (sensu Rauhut 2003), and
Tetanurae is lobular-shaped in cranial aspect (Sereno
1999). As is the case among other neotheropods (e.g.
Coelophysis, Gojirasaurus, Liliensternus, Masiakasaurus,
Allosaurus, Torvosaurus), the caudolateral surface of the
distal tibia of Zupaysaurus is concave, suggesting that
this condition does not represent a tetanuran synapo-
morphy (contra Arcucci and Coria 2003, see below),
but an apomorphy of the Neotheropoda (Ezcurra and
Novas 2005).
In Zupaysaurus, the distal tibial facet for the
articulation with the ascending process of
the astragalus is well developed (Figure 3E), as is the
case in Herrerasaurus, Dilophosaurus, Liliensternus,
Gojirasaurus, and Coelophysis. In contrast, this facet is
considerably reduced in basal members of the
Tetanurae. Moreover, in Zupaysaurus a lateroventral
notch separates the distal facet for the ascending
process from the outer malleolus, closely resembling
the morphology seen in basal dinosauriforms (e.g.
Silesaurus, Dilophosaurus, Liliensternus, Coelophysis,
Herrerasauridae), but differing from tetanurans in
which the lateroventral notch of the distal tibia is
absent.
An interesting feature present on the distal tibia of
Zupaysaurus, is a deep caudomedial notch for the
reception of a caudomedial prominence of the
astragalus (Figure 3). Such excavation is widely
distributed among Neotheropoda (e.g. Dilophosaurus,
Liliensternus, Gojirasaurus, Coelophysis, Sinraptor,
Figure 4. Zupaysaurus rougieri right tarsus. (A) cranial, (B) caudal, (C) dorsal, (D) ventral, (E) lateral, and (F) medial views. Abbreviations:
ap, ascending process; cap, caudal ascending process; das, dorsal articular surface; dc, diagonal crest; ff, fibular facet; tf, tibial facet.
Figure 5. Zupaysaurus rougieri articulated right distal tibia-fibula and tarsus. (A) cranial, (B) caudal, and (C) medial views.
M. D. Ezcurra & F. E. Novas40
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Allosaurus), but it is more deeply excavated as well as
medially open in Zupaysaurus, thus constituting an
autapomorphic feature of this genus (Arcucci and
Coria 2003) (Figure 3D,E).
The distal end of fibula exhibits a slender shaft,
which is distally expanded. It articulates on the
proximal surface of the calcaneum, and laterally with
the ascending process of the astragalus. The fibula of
Zupaysaurus does not flare craniomedially as charac-
teristically occurs in adult specimens of Coelophysis
bauri (Raath 1990) and Syntarsus (Rowe 1989).
Tarsus. The astragalus and calcaneum are firmly
fused to each other (Arcucci and Coria 2003);
however, they remain unfused from both tibia and
fibula (Figure 4). The tarsus is almost complete and
well preserved. The ascending process of the
astragalus is low, robust, and pyramid-shaped, thus
resembling Liliensternus, Coelophysis bauri (Rowe and
Gauthier 1990), C. rhodesiensis (Raath 1977), and
Syntarsus (Rowe 1989), but in contrast with the
more derived condition present in tetanurans (e.g.
To r v o s a u r u s , Allosaurus) in which the ascending
astragalar process is higher and more craniocaudally
compressed.
In Zupaysaurus the craniolateral surface of the
ascending process exhibits a wide fossa (Figures 4A,
5A), as is the case in Dilophosaurus (Tykoski 2005, fig
94c), L. liliensterni (HMN MB R. 2175), Coelophysis
rhodesiensis (Raath 1990), C. bauri (Tykoski 2005, fig
97c), and Syntarsus (Tykoski 2005, fig 94b). The
ascending process of the astragalus exhibits a
moderately developed proximal articular surface for
tibial support. In this regard, Zupaysaurus resembles
Liliensternus and Coelophysis, differing from cerato-
saurians and tetanurans, in which the proximal
articular surface of the ascending process is more
craniocaudally reduced. In sum, the astragalar
morphology of Zupaysaurus is congruent with the
“coelophysoid” pattern, present in Liliensternus,
Syntarus,andCoelophysis. Thus, we dismiss the
interpretation of Arcucci and Coria (2003) about the
“intermediate” tarsal morphology of Zupaysaurus,
between basal theropods (e.g. Herrerasaurus and
ceratosaurs) and more derived tetanurans.
The cranial surface of the astragalar body presents a
series of shallow fossae, as occurs in Dilophosaurus
wetherilli (MACN 18686). The proximal articular
surface of the astragalus is strongly concave. A sharp
diagonal crest, extending caudolaterally from the
ascending process, divides the dorsal surface of the
astragalus in two distinct tibial and fibular facets
(Figure 4C). On the caudomedial corner of the
proximal astragalar surface there is a strongly devel-
oped articular process, which fits within a deep caudal
notch of the distal tibia (Figures 4F, 5B,C); a structure
widely present among other basal theropods (e.g.
Liliensternus, Dilophosaurus, Sinraptor, Allosaurus).
The calcaneum is hemicylindrical and transversely
compressed. Its lateral surface is slightly concave, as
occurs in most theropods. The caudal end is more
tranversely compressed than the cranial half of the
bone. The distal end of the fibula articulates with
the dorsal surface of the calcaneum, as well as with the
continuous proximal astragalar surface that is
bounded by the ascending process and the diagonal
crest. Zupaysaurus retained the theropod plesio-
morphic condition of a calcaneum that only articu-
lates with the fibula (Figure 4C). This is different from
derived tetanuran taxa (e.g. Allosaurus, Acrocantho-
saurus) in which the calcaneum receives the fibula as
well as the lateral extremity of the outer malleolus.
Furthermore, in Zupaysaurus, this proximal articula-
tion with the fibula is craniocaudally extended along
the entire proximal surface of the calcaneum,
resembling other basal dinosaurs, including the
coelophysoids Dilophosaurus (MACN 18686) and
Liliensternus (HMN MB R. 2175). On the other
hand, in Coelophysis rhodesiensis (Raath 1990) and
Syntarsus (Tykoski 2005), the proximal articular
surface for the reception of the fibula is excluded
from the caudal border of the calcaneum, resembling
the condition of more dervied theropods.
Figure 6. Zupaysaurus rougieri left caudoproximal portion of
scapulocoracoid in caudolateral view. Abbreviations: ap,
acrocoracoid process; gf, glenoid fossa; s, suture; sbb, subglenoid
buttress; sbf, subglenoid fossa; spb, supraglenoid buttress.
Phylogenetic relationships of Zupaysaurus 41
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Elements of the associated material
Several isolated bones that were found in association
with the holotype specimen of Zupaysaurus have been
considered by Arcucci and Coria (2003) as belonging
to an individual of uncertain taxonomic affinities.
These bones include a partially preserved left
scapulocoracoid, a fragmentary right ilium, the
proximal end of a right pubis (fused to the ilium),
the distal ends of left and right femora, and a proximal
left tibia.
Scapulocoracoid. The proximal end of the left
scapula and a portion of the fused coracoid are
present. The glenoid fossa is deep, with strongly
developed supraglenoid and subglenoid buttresses
(Figure 6). The acrocoracoidal process is represented
by a caudoventrally oriented and well-developed
tuberosity, and the subglenoid fossa is deeply
excavated; features that are both congruently present
in other coelophysoids (e.g. Liliensternus, Coelophysis).
A second, less marked tuberosity is located close to the
caudal margin of the glenoid fossa, approximately over
the scapulocoracoid suture, a feature that seems to be
present in Coelophysis rhodesiensis (QG 1). The
caudoventral process of the coracoid of Zupaysaurus
is poorly developed. In Liliensternus this process is also
reduced (HMN MB R. 2175), but slightly better
developed than in Zupaysaurus. On the contrary, this
process is more developed (i.e. it nearly exceeds the
caudal level of the subglenoid buttress) in the
coelophysoids Syntarsus and Coelophysis, Dilopho-
saurus, the ceratosaurian Ceratosaurus, and in the
basal tetanurans Edmarka and Allosaurus. In sum, the
morphology of that scapulocoracoid fits well with that
of coelophysoids, and we refer this element to
Zupaysaurus.
Ilium and pubis. The preserved iliac blade is
surprisingly low (Figure 7), in contrast with the
dinosaurian condition in general, and theropodian
condition in particular, in which the ilium is
Figure 7. Basal saurischian? right ilium. (A) caudal, (B) lateral, (C) dorsal, and (D) ventral views. Abbreviations: bf, brevis fossa; ip, ischial
peduncle; lr, longitudinal ridge; p, pubis; pap, postacetabular process; pat, pubic antitrochanter; pp, pubic peduncle; r, ridge; sc,
supraacetabular crest.
M. D. Ezcurra & F. E. Novas42
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dorsoventrally deep above the acetabulum. Since the
dorsal margin of the ilium is transversely thick and
rounded, the iliac blade gives the impression of not
being broken off, albeit the dorsal margin of the ilium
could be also strongly weathered. The dorsal margin
of the ilium describes a sigmoidal curvature in lateral
view. A prominent and dorsolaterally projected
transversal ridge, almost in contact with the supraa-
cetabular crest, is present at the level of the rostral
margin of the acetabulum, and seems to correspond to
the base of the preacetabular process. The supraace-
tabular crest is laterally projected, mainly at the level
of the pubic peduncle and cranial margin of the
acetabulum. In contrast with basal neotheropods (e.g.
Liliensternus, Coelophysis, Syntarsus, Dilophosaurus,
Ceratosaurus, Allosaurus), the supraacetabular crest
finishes at the cranial level of the ischial peduncle. It is
laterally projected, and does not obscure the
craniodorsal border of the acetabulum in lateral
view. Furthermore, the supraacetabular crest is clearly
separated from the lateral margin of the brevis fossa,
representing the plesiomorphic condition of the
Neotheropoda. The pubic peduncle of the ilium is
ventrally projected, in contrast with the cranioven-
trally oriented and pronouncedly kinked articular
facet that characteristically occurs in coelophysoids
(Rauhut 2003). The preserved portion of the brevis
fossa, corresponding to its cranialmost portion, is
dorsoventrally shallow (Figure 7A,D), in contrast with
the well excavated condition of basal theropods (e.g.
Coelophysis, Liliensternus). Caudally protracted from
the ischial peduncle, a lamina delimits the brevis fossa
medially. The distal aritcular surface of the ischial
peduncle is reduced, resembling the condition of basal
saurischians (e.g. Plateosaurus, Staurikosaurus, Guai-
basaurus, Herrerasaurus). The acetabulum seems to be
fully open, as in the case in the majority of dinosaurs,
albeit its dorsal border is slightly crushed. Only the
proximal end of the pubis is preserved, showing a
prominent and caudally projected antitrochanter.
The set of features listed above for the preserved
portions of the ilium and pubis (e.g. ventrally projected
articular facet of pubic peduncle, supraacetabular
crest laterally projected and not extended over the
ischial peduncle, supraacetabular crest well separated
from the lateral magin of the brevis fossa, articular
facet of the ischial peduncle reduced) strongly suggests
that the preserved pelvic elements found in association
with the holotype of Zupaysaurus rougieri do not belong
to a member of the Coleophysoidea, neither of the
Theropoda. On the other hand, the presence of a
brevis shelf and fully open acetabulum approach the
Figure 8. Zupaysaurus rougieri left femora. (A) caudal, (B) cranial, (C) lateral, and (D) distal views. Abbreviations: cig, caudal intercondylar
groove; fc, fibular condyle; fcg, fibular condyle groove; tc, tibial condyle; tfc, tibiofibular crest.
Phylogenetic relationships of Zupaysaurus 43
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typical dinosaurian condition (Novas 1996), resem-
bling the overall iliac morphology of basal saurischian
dinosaurs.
Femur. An incomplete distal end of a right femur
(Figure 8) was found in association with the holotype of
Zupaysaurus rougieri, but referred by Arcucci and Coria
(2003) to the “associated material because of its
comparative smaller size. As pointed out in the original
description, a developed medial epicondyle is present
over the tibial condyle (2003), a morphology that agrees
with that present in coelophysoids (e.g. Coelophysis,
Liliensternus), as well as in more derived theropods
(e.g. Ceratosaurus, Sinraptor, Allosaurus). In fact, this
feature seems to constitute a probable diagnostic feature
of Neotheropoda.
A deep caudal intercondylar groove is present, but
the area of the popliteal fossa is not preserved.
A marked but shallow groove is present between the
lateral face of the crista tibiofibularis and the fibular
condyle. This groove differs from the strongly marked
and ventrally situated ventral groove of some basal
theropods, previously considered as a synapomorphic
character of a monophyletic Ceratosauria (sensu
Rowe and Gauthier 1990). The morphology
described above for Zupaysaurus is also shared by
some specimens of Coelophysis (MCZ 4779), Cerato-
saurus (USNM 4735) and Masiakasaurus (Carrano
et al. 2002).
In distal view, the fibular condyle exhibits a spherical
surface, and is considerably larger than the tibial
condyle. This condyle is well diferentiated from the
tibiofibular crest by a shallow troclea fibularis and a well
marked groove of the fibular condyle, as occurs in
coelophysoids and ceratosaurians (Sereno 1999). The
tibiofibular crest is well deferentiated from the shaft,
showing a caudolaterally oriented main axis and a
convex surface on its medial surface (Figure 8), as in
several basal theropods (e.g. Coelophysis MCZ 4779,
Coelophysis rhodesiensis QG 1, L. liliensterni HMN MB R.
2175, Dilophosaurus, Ceratosaurus nasicornis USNM
Figure 9. Skulls of severaltheropodsin (A), (B), (C)leftlateral and(D), (E), (F)dorsal views. (A) Syntarsus kayentakatae,(B)Coelophysis bauri,(C),
(D) Zupaysaurus rougieri,(E)and(F)Allosaurus fragilis. Not to scale. (A), after Tykoski 1998; (B), after Colbert 1989; (E), (F), after Madsen 1976).
Figure 10. Close-up of the caudodorsal corner of right lacrimal of
Zupaysaurus rougieri in lateral view. Abbreviations: op, opening; pn,
pneumatic opening. Other abbreviations as in Figure 1.
M. D. Ezcurra & F. E. Novas44
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4735, Masiakasaurus), some dinosauriforms (e.g.
Silesaurus), prosauropods (e.g. Riojasaurus), as well as
basal archosauriforms (e.g. Euparkeria). In contrast, in
Herrerasaurus and Tetanurae (e.g. Streptospondylus,
Sinraptor, Acrocanthosaurus) the tibiofibular crest is
directly caudally oriented and square-shaped. The
caudal intercondilar groove is very deep and wide, as
in other neotheropods, in contrast with the transversely
compressed groove of Herrerasaurus. The tibial condyle
is caudally extended at the same level of the tibiofibular
crest. The ancestral condition of a convex cranial surface
of the distal femur was retained in Zupaysaurus (Arcucci
and Coria 2003). In fact, the cranial intercondylar
groove is also absent in Herrerasaurus (Novas 1993),
Coelophysis (MCZ 4779), and Liliensternus liliensterni
(HMN MB R. 2175). Ceratosaurus nasicornis (USNM
4735) lacks the cranial intercondylar groove, and the
cranial surface is planar. On the other hand, Dilopho-
saurus exhibits a slightly concave cranial surface. In
contrast, in Masiakasaurus and other abelisauroids the
cranial margin present a shallow intercondylar groove
(Carrano et al. 2002). In Tetanurae this intercondylar
groove is deeply developed.
Tibia. Among the associated material of Zupaysaurus
an incomplete proximal end of a left tibia is present.
This proximal articular extremity preserves most of
the cranial portion, lacking both caudal condyles. The
cnemial crest is low, when compared with the
prominent crest exhibited by neotheropod dinosaurs
(e.g. Gojirasaurus, Syntarsus, Coelophysis rhodesiensis,
Liliensternus, Masiakasaurus). This plesiomorphic trait
distinguishes this partial tibia from those of neother-
opod taxa, including coelophysoids. On the other
hand, this condition resembles to that of basal
Dinosauriformes (e.g. Marasuchus) and basal Dino-
sauria (e.g. Herrerasaurus, Saturnalia). The plesio-
morphic cranial development of the cnemial crest,
contrast with the presence of a deep fossa separating
the crest from the fibular condyle, resulting in a
strongly laterally curved cnemial crest, a feature
shared by most neotheropods (e.g. Coelophysis,
Syntarsus, Masiakasaurus, Allosaurus), but not by
non-neotheropodan dinosaurs. There is no trace of a
knee extensor groove on the craniolateral surface of
the cnemial crest.
Most of the elements of the “associated materials”
exhibit coelophysoid or neotheropod features (e.g.
scapulocoracoid, distal ends of femora, proximal end
of tibia), and for this reason are referred to
Zupaysaurus. Arcucci and Coria (2003) considered
the mentioned bones as associated materials of a
smaller individual of uncertain affinities. However,
the left scapulocoracoid, as well as the distal femora,
are congruent in size with the distal tibia and tarsus.
In fact, the postcranial bones of coelophysoids seem to
be proportionally smaller than the skull, due to its
enlongate nature, principally the strongly lengthened
snout. The same condition is present in Zupaysaurus.
Moreover, the proportions between skull and post-
cranial elements of Zupaysaurus are in accord with the
gracile morphotypes of the Ghost Ranch Coelophysis
specimens, characterized by elongated skulls and
proportionally smaller arms (Colbert 1989) (e.g.
AMNH 7223).
Figure 11. Distal tibiae and tarsals of several theropods. (A), (D), and (G) Zupaysaurus rougieri. (B), (E), and (H) Liliensternus liliensterni.
(C), (F), and (I) Allosaurus fragilis. (A), (B), and (C) distal tibiae in cranial views. (D), (E), and (F) distal tibiae in distal view. (G), (H), and (I)
proximal tarsals in cranial view. Not to scale. (C, after Madsen 1976).
Phylogenetic relationships of Zupaysaurus 45
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The exception is the incomplete ilium, which
obviously belongs to a different animal, almost
probably a non-neotheropodian basal saurischian.
Discussion
We will first discuss the characters that were originally
considered to support the tetanuran affinity of
Zupaysaurus (Arcucci and Coria 2003), and then
analyse the features that this taxon shares with
Coelophysoidea and less inclusive groups.
Review of characters originally proposed to support the
tetanuran affinity of Zupaysaurus
Arcucci and Coria (2003) listed the following features:
1. Large maxillary fenestra, caudally positioned
(Arcucci and Coria 2003:228, character number 9
Figure 12. Cladograms showing (A) the phylogenetic relationships of Zupaysaurus rougieri and other coelophysoids within the Dinosauria,
and (B), (C) close-up of the coelophysoid interrelationships. (A) Strict consensus of the fourteen trees resulted from the first phylogenetic
analysis with all taxa included, (B) majority consensus tree of the fourteen trees resulted from the first phylogenetic analysis with all taxa
included, and (C) strict consensus of the two trees resulted from the analysis of the matrix with the exclution of Procompsognathus. Numbers
alongside each node in (C) indicate number of unambiguous characters supporting that node. Numbered nodes are as follows: I, Ornithischia;
II, Sauropodomorpha; III, Ceratosauria; IV, Allosauroidea.
Figure 13. Close-up of the rostral end of the left maxilla and
dentary of Zupaysaurus rougieri. Abbreviations: uta, upturned
alveolar margin. Other abbreviations as in Figure 1.
M. D. Ezcurra & F. E. Novas46
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in data matrix). In the right maxilla of Zupaysaurus,
almost two subcircular pneumatic excavations
exist on the rostral corner of the antorbital fossa
(Figure 1A,C). Arcucci and Coria (2003)
described the rostral excavation at the beginning
of the maxillary ascending ramus as a promaxillary
foramen, and the caudalmost fossa was interpreted
as a maxillary fenestra. This latter opening,
although also blind, differs from the maxillary
sinus (Madsen and Welles 2000) present in several
non-tetanuran basal neotheropods (e.g. Cerato-
saurus, Coelophysis bauri, Coelophysis rhodesiensis,
Masiakasaurus) in its position and size, but it is
congruent with the maxillary fenestra of the
tetanurans (Arcucci and Coria 2003) (Figure 9E).
In fact, Zupaysaurus resembles basal tetanurans
such as Dubreuillosaurus (Allain 2002) in the
presence of a blind maxillary fenestra, in contrast
with the condition of more derived tetanurans (e.g.
Allosaurus, Acrocanthosaurus), in which this pneu-
matic opening pierces the lamina medialis of the
maxillary ascending ramus (Witmer 1997). In
sum, we agree with Arcucci and Coria (2003) that,
within the antorbital fossa, both promaxillary
foramen and maxillary fenestra are present, but we
consider this condition as convergently acquiered
with tetanuran theropods.
2. Antorbital maxillary teeth (Arcucci and Coria
2003:228, character number 6 in data matrix).
Character listed by Arcucci and Coria (2003) in
the abstract and main text as shared only with
tetanurans, but in the data matrix it is shared by a
more inclusive ingroup, the Averostra. Arcucci and
Coria (2003) described that the maxillary tooth
row of Zupaysaurus is rostral to the orbit. However,
it could be observed that the last maxillary teeth is
situated ventrally to the rostral margin of the orbit
(Figure 1A), as occurs in Herrerasaurus and other
basal theropods, including Coelophysis and Syntar-
sus (Figure 9A). In ceratosaurians the maxillary
tooth row is caudal to the internal antorbital
fenestra caudal margin. On the other hand, in
Dilophosaurus and Tetanurae (e.g. Torvosaurus,
Sinraptor, Allosaurus, Acrocanthosaurus, Carcharo-
dontosaurus) the maxillary tooth row does not
extend caudal to the internal antorbital fenestra.
Overall, the maxillary tooth row of Zupaysaurus
resembles the condition present in basal taxa, such
as coelophysids (e.g. Coelophysis, Syntarsus),
ceratosaurians (e.g. Carnotaurus, Ceratosaurus),
Eoraptor,andHerrerasaurus, the maxillary tooth
rows of which extend caudal to the internal
antorbital fenestrae.
3. Presence of a pneumatized lacrimal recess
(Arcucci and Coria 2003:228, character number 7
in data matrix). Arcucci and Coria (2003:228)
offered a different alternative definition of the
character in the data matrix as “pneumatized
lacrimal and jugal”, indicating that this state is
shared by Zupaysaurus and tetanurans, although
the jugal of the former lacks pneumatic features, at
leastontheexternalsurface.Zupaysaurus exhibits a
recess on the lateral surface of its lacrimal, forming
the lacrimal antorbital fossa (Witmer 1997). The
lacrimal recess shows several subcircular pneu-
matic openings in its caudodorsal corner
(Figure 10). This group of excavations form a
pneumatic system widely subdivided. Such an
extensive pneumatic excavation system, from the
lacrimal recess to inside the lacrimal shaft, has not
been described for any other coelophysoid, and
seems to be derived in Zupaysaurus (Arcucci and
Coria 2003). The lacrimial of Dilophosaurus is
highly specialized in order to form the pair of high
Figure 14. Jugals of several saurischians in lateral view. (A)
Plateosaurus, (B) Zupaysaurus, (C) Syntarsus kayentakatae, and (D)
Allosaurus. Not to scale. (A), after Galton 1984 and Tykoski 2005;
(C), after Tykoski 2005; (D), after Madsen 1976).
Phylogenetic relationships of Zupaysaurus 47
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naso-lacrimal crests, and the condition from which
it is derived is uncertain (Rauhut pers. comm.).
Among the Ceratosauria, a single opening of
considerable size is present in the caudodorsal
margin of the lacrimal recess of Ceratosaurus
(Rauhut 2003), whereas lacrimal pneumatization
is also present in at least some abelisaurs, but not
visible laterally due to an overgrowth of the lateral
bone surface of the caudodorsal corner (e.g.
Majungatholus) (Rauhut pers. comm.). On the
other hand, the lacrimal pneumatization in
Tetanurae is represented by a single opening within
the lacrimal antorbital fossa (e.g. Eustreptospondy-
lus; OUM J 13558) or a system of multiple openings
(e.g. Magnosaurus, Allosaurus, Ornitholestes, Sin-
raptor, Carcharodontosaurus). The subdived pneu-
matic system on the lacrimal recess of Zupaysaurus,
considered as one of the synapomorphic characters
of Tetanurae (Sereno 1999), could constitute the
plesiomorphic condition for Neotheropoda, and its
absence in Coelophysis and Syntarsus a synapo-
morphic character of coelophysids.
Furthermore, a second rostrocaudally elongated
opening is present rostral to the pneumatic
excavations described above (Figure 10). A similar
opening has been described for other theropods
(e.g. Sinraptor, Allosaurus), but its function is
controversial. Its interpretation as a pneumatic
diverticulum of the nasal cavity (Witmer 1987)
aside, Currie and Zhao (1993) have argued that this
opening may have housed the superior nasal artery
and the ramus nasalis of the ophthalmic nerve. On
the other hand, Madsen (1976) proposed the
presence of a gland, possibly a specialized lacrimal
gland to keep the eye moist.
4. Tibia transversely expanded (Arcucci and
Coria 2003:228, character number 19 in data
matrix). The tibia of Zupaysaurus is not transversely
expanded to the degree seen in Tetanurae (e.g.
To r v o s a u r u s , Allosaurus)(Figure11C,F).Inthe
Argentine taxon, the distal end of the tibia is almost
identical (morphologically and proportionally) to
that of the coelophysoid Liliensternus
(Figure 11A,B,D,E). In fact, the distal end of the
tibia of Zupaysaurus presents a moderate transver-
sal expansion, represented by the lateral develop-
ment of the lateral malleolus (Arcucci and Coria
2003), overlapping only partially the fibula
caudally, as occurs in basal theropods (e.g.
Herrerasaurus, Liliensternus liliensterni HMN MB
R. 2175). Nevertheless, the basal theropod
Herrerasaurus presents a lateral process only slightly
laterally developed (Novas 1989), in contrast with
coelophysoids. In contrast to other theropods, the
strong transversal development of the distal end of
the tibia of Tetanurae is formed by a strong lateral
extension of the lateral malleolus, overlapping the
fibula entirely in caudal view.
5. Tibia with a caudolaterally concav e distal end
(character listed by Arcucci and Coria 2003, in the
Abstract and main text, but not in data matrix). As
indicated by Arcucci and Coria (2003), a distinct
ridge exist on the distal end of tibia separating
medial and lateral sides, with the latter being
slightly concave (Figure 11E). In this context, these
authors (Arcucci and Coria 2003) have indicated
that this tibial morphology coresponds to that of
basal tetanurans, like Allosaurus, Giganotosaurus,
and Sinraptor, rather than to the planar or convex
condition of Dilophosaurus and Herrerasaurus.In
fact, the caudal surface of the distal end of the tibia
of Herrerasauridae, basal dinosauriforms (e.g.
Marasuchus, Silesaurus), and Sauropodomorpha
(e.g. Riojasaurus) exhibits a planar or slightly
convex lateral margin. However, the character
described by Arcucci and Coria (2003) as shared by
Zupaysaurus and Tetanurae is also clearly present in
other basal neotheropods, such as Liliensternus
liliensterni (HMN MB R. 2175) (Figure 11E),
Coelophysis, Gojirasaurus, the basal abelisauroid
Masiakasaurus, and an undescribed specimen of
Dilophosaurus (Rauhut 2003, fig. 45B). Addition-
ally, Arcucci and Coria (2003) mentioned a convex
or planar caudolateral margin in the distal end of
the tibia of Dilophosaurus. Interestingly, the widely
described and illustrated holotype specimen of
Dilophosaurus differs from other coelophysoids and
other neotheropods, including the undescribed
specimen of the same genus, among other
characters, in the presence of a convex lateral
margin in the caudal surface of the tibia. Thus we
consider here the presence of caudolaterally
concave distal end of the tibia a character diagnostic
of Neotheropoda.
Arcucci and Coria (2003) also listed (but without
discussion in the text, nor inclusion in the data matrix)
several diagnostic characters of Tetanurae that are
present in Zupaysaurus, such as: “lateral temporal
fenestra reduced and key hole-shaped”, “lacrimal horn
developed as a low crest or ridge”, “fibula with distal end
expanded almost double the shaft width”, “ascending
process of astragalus cranially positioned”. These
features, however, deserve the following comments: 1)
a lateral temporal fenestra reduced and key-hole-shaped
is present in Allosaurus but also in coelophysids
(Figure 9A,C,E); 2) a high lacrimal horn (characteristic
of averostrans) is absent in Zupaysaurus (Figure 1,
9C,D); 3) the fibula of Zupaysaurus is distally robust,
exceeding the craniocaudal diameter of the shaft
(Figure 5A,B), and thus differs from the tetanuran
condition, in which the distal fibula is equal or smaller
than mid-shaft (Sereno et al. 1996, Harris 1998); 4) an
ascending process of the astragalus that is cranially
positioned represents a plesiomorphic feature for at least
Dinosauria. Moreover, the morphology of the ascending
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astragalar process in Zupaysaurus is almost identical to
that of the coelophysoid Liliensternus, in which this
process retains a wide proximal surface for articulation
with distal tibia. In this respect, Zupaysaurus clearly
differs from tetanurans (e.g. Torvosaurus, Allosaurus)
in which the ascending process is more laminar
(i.e. craniocaudally flattened).
In sum, most characters used by Arcucci and Coria
(2003) to support Zupaysaurus as a primitive
Tetanurae are problematic.
The phylogenetic relationships of Zupaysaurus
Phylogenetic analyses
The above comparisons and discussions showed
that the anatomy of Zupaysaurus is in accord to that of
the basal-most neotheropods than to that of tetanur-
ans. In the following section, we will analyse, with the
information provided by the analysis of a data matrix,
the possible phylogenetic position of this taxon within
the Neotheropoda.
Methods
The matrix is composed of 253 characters and 26
taxa; character polarity was determined using the
basal dinosauriform Silesaurus opolensis Dzik (2003)
and some basal ornithischian taxa (Heterodontosaurus
tucki Crompton and Charig 1962, Lesothosaurus
diagnosticus Galton 1978, Scutellosaurus lawleri Colbert
1981) as successive outgroups. Twenty-two taxa were
used as ingroups: Acrocanthosaurus atokensis Stovall
and Langston (1950), Allosaurus fragilis Marsh 1877,
Carnotaurus sastreri Bonaparte 1985, Ceratosaurus
nasicornis Marsh 1884 (following Rauhut (2003) the
species C. dentisulcatus and C. magnicornis (Madsen
and Welles 2000) are here interpreted as synonymous
of C. nasicornis), Coelophysis bauri Cope 1887,
Coelophysis rhodesiensis Raath 1969 (see systematic
nomenclature), Dilophosaurus wetherilli Welles 1954,
Eoraptor lunensis Sereno et al. 1993, Gojirasaurus quayi
Carpenter 1997, Herrerasaurus ischigualastensis Reig
1963, Liliensternus liliensterni von Huene 1934,
Masiakasaurus knopfleri Sampson et al. 2001, Plateo-
saurus longiceps Jaekel 1913-14, Procompsognathus
Fraas 1913, Saturnalia tupiniquim Langer et al. 1999,
Segisaurus halli Camp 1936, Sinraptor dongi Currie
and Zhao 1993, Spinosauridae Stromer 1915 (due to
the the fragmetary skeletons of the best known
spinosaurid taxa, the family Spinosauridae was here
used as an operational taxonomic unit (OTU) as a
whole; characters regarding to the Spinosauridae were
codifed on basis of Baryonyx walkeri Charig and
Milner 1986, Irritator challengeri Martill et al. (1996),
Spinosaurus aegyptiacus Stromer 1915, and Suchomi-
mus tenerensis Sereno et al. 1998), Syntarsus
kayentakatae Rowe 1989, Thecodontosaurus antiquus
Morris 1843 (recently Galton (2005) has pointed out
that T. caducus is a junior synonym of T. antiquus, here
the OTU T. antiquus include both supposed species of
Thecodontosaurus), Torvosaurus tanneri Galton and
Jensen 1979, and Zupaysaurus rougieri Arcucci and
Coria (2003).
The anatomical data on the above mentioned taxa
was coded on the basis of the the material examined
(see studied specimens), their more descriptive
published literature, and the codings of the following
authors (Tykoski 1998, 2005; Carrano et al. 2002,
2005; Yates 2003; Rauhut 2003; Sereno et al. 2004;
Langer 2004; Tykoski and Rowe 2004).
The data matrix was analysed using NONA
program ver. 2.0 (Goloboff 1993) under 100
replications, with search strategy of multiple tree
bisection-reconnection of branch-swapping (multiple
TBR þ TBR), and unambiguous optimization.
Results
The result were fourteen trees with 711 steps, with a
consistency index (C.I.) of 0.44 and a retention index
(R.I.) of 0.69, in which all the trees unequivocally
showed Zupaysaurus rougieri as a member of the
Coelophysoidea (Figure 12A). Furthermore, the four-
teen trees showed coelophysoid outgroup relationships
fully resolved resembling the analyses of previous
authors (e.g. Sereno et al. 1993; Sereno 1999; Carrano
et al. 2002, 2005; Rauhut 2003), with the Ornithischia
(Lesothosaurus þ (Scutellosaurus þ Heterodotnosaurus))
as the sister group of the Saurischia, and within this clade
the Sauropodomorpha (Saturnalia þ (Thecodonto-
saurus þ Plateosaurus)) as the sister taxon of a typical
Theropoda (Eoraptor þ (Herrerasaurus þ Neothero-
poda)), sensu Sereno et al. (1993). Within the
Neotheropoda, the fourteen trees depicted a mono-
phyletic Averostra (see systematic nomenclature),
composed by Ceratosauria (Ceratosaurus þ (Masiaka-
saurus þ Carnotaurus)) and Tetanurae (Torvosaurus þ
Spinosauridae þ (Allosaurus þ (Acrocanthosaurus þ
Sinraptor))), as sister taxon of a monophyletic Coelo-
physoidea (Dilophosaurus þ (Liliensternus þ Coelo-
phsis)), sensu Holtz (1994) (Holtz 1994, 2000;
Tykoski 1998, 2005; Sereno 1999; Tykoski and Rowe
2004; Ezcurra and Novas 2005; Carrano et al. 2005;
contra Carrano et al. 2002; Rauhut 2003).
Within the Coelophysoidea, the trees also invariably
showed Dilophosaurus and Liliensternus as successive
sister taxa of the other coelophysoids (Segisaurus,
Procompsognathus, Coelophysis, Syntarsus, Gojirasaurus,
Zupaysaurus). None of the trees supported a Pro-
compsognathinae (Segisaurus þ Procompsognathus)
sensu Sereno (1999), as Carrano et al. (2005) also
reported; neither Syntarsus kayentakatae more closely
related to Coelophysis rhodesiensis ( ¼ S. rhodesiensis)
than to Coelophysis bauri.
The strict consensus of the 14 obtained trees depicted
a tricotomy within the Tetanurae (To r v o s a u r u s þ
Phylogenetic relationships of Zupaysaurus 49
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Spinosauridae þ Allosauroidea) and a polytomy within
a lesser inclusive clade of the Coelophysoidea
(Dilophosaurus þ (Liliensternus þ other coelophy-
soids)). On the other hand, the majority consensus
tree (Figure 12B) showed Coelophysoidea composed of
Dilophosaurus and Liliensternus as the more basal
members of the clade, and the sister taxa of a tricotomy
composed by the other coelophysoids, with a frequency
of 85%. Within this tricotomy, two distinct nodes, both
with a frequency of 85%, are discernible. The first
includes Gojirasaurus and Syntarsus kayentakatae,and
the second the genus Coelophysis (C. bauri þ
C. rhodesiensis).
A second test was carried out excluding Procompsog-
nathus from the analysis. The new result was two trees
with 710 steps, C.I. of 0.44, and R.I. of 0.69. When the
hard collapse option on unsupported nodes and the
strict consensus were applied, the interrelationships of
the coelophysoid outgroups kept the topology of the first
analysis (Figure 12A). Within the Coelophysoidea, it
shows the same topology of the majority consensus tree
of the first analysis, but without Procompsognathus,
i.e.: (Dilophosaurus þ Liliensternus þ (Zupaysaurus þ
Segisaurus þ ((Syntarsus kayentakatae þ Gojirsaurus) þ
Coelophysis))).
A bootstrap analysis was carried out with the data
matrix with the exclution of Procompsognathus,
performed with 100 replications (coelophysoid out-
groups bootstrap values are detailed in Appendix 3).
Coelophysoidea is not well supported with a bootstrap
value of 49%. The node composed by coelophysoids
more derived than Dilophosaurus is supported by a
bootstrap value of 76%, whereas the node that include
Zupaysaurus, Segisaurus, Gojirasaurus, Syntarsus, and
Coelophysis has support value of 52%. Within
Coelophysoidea, the clade better supported by the
bootstrap encloses both species of Coelophysis (C. bauri
and C. rhodesiensis), with a support of 87%. Syntarsus
kaynetakatae was placed closer to C. rhodesiensis than
to the other coelophysoids (i.e. monophyletic Syn-
tarsus”) in 3% of the trees. Furthermore, the
averostran clade is well supported with a bootstrap
value of 91%, in contrast with a poor supported
monophyletic “Ceratosauria” (i.e. Coelophysoidea þ
Neoceratosauria) node with a bootstrap value of 1%.
Interestingly, the support for the clade composed of
Dilophosaurus þ Averostra is subequal to than that of a
monophyletic Coelophysoidea (sensu Holtz 1994),
exhibiting a bootstrap value of 47%. Regarding
the phylogenetic hypothesis of Zupaysaurus as
more derived than the Coelophysoidea (see Arcucci
and Coria 1998, 2003), the bootstrap analysis
only depicted a node enclosing Zupaysaurus þ
Dilophosaurus þ Averostra with a very low support
value of 2%.
In sum, the phylogenetic analyses carried out here
showed that Zupaysaurus is unequivocally a member of
the Coelophysoidea, and clearly not a basal Tetanurae.
Derived coelophysoid features present in Zupaysaurus
As the comparisons made above indicate and the
result of the data matrix support, the cranial and
postcranial anatomy of Zupaysaurus is more congruent
with that of coelophysoid theropods (Carrano et al.
2005; Ezcurra and Novas 2005; Tykoski 2005),
rather than averostran theropods (Ceratosauria þ
Tetanurae) and specially tetanurans (contra Arcucci
and Coria 2003). In fact, Zupaysaurus shares the
following synapomorphies of the Coelophysoidea (and
lesser inclusive clades of the Superfamily), that clearly
demonstrate that Zupaysaurus is a member of this
clade of basal theropods:
Coelophysoidea (stem based node that encloses all
theropods closer to Coelophysis than to Ceratosaurus,
Padian et al. 1999)
(1) Skull length (premaxilla-quadrate condyle)
versus skull height (quadrate condyle-dor-
sal most edge of parietal) equal or more
than 3 times (Forster 1999; Sereno 1999;
Tykoski 2005). As previously indicated, coelo-
physoid theropods are characterized by enlon-
gated, and proportionally low skulls (Figure 9).
The length of the skull (measured from the
rostral tip of the premaxilla to the caudal tip of
the quadrate condyle) represents three, or more
than three times the caudal height of the skull
(measured from the ventral tip of the quadrate
condyle to the dorsal-most edge of the parietal)
in Dilophosaurus, Coelophysis rhodesiensis, Syntar-
sus kayentakatae, (Sereno 1999), Zupaysaurus,
and Herrerasaurus. Other basal dinosaurs exhibit
a proportionally shorter skull, with a length lower
than 2 times its caudal height (e.g. Lesothosaurus,
Eoraptor, Thecodontosaurus, Ceratosaurus, Allo-
saurus, Sinraptor). Among the Tetanurae, albeit
only fragmentary or partial cranial remains are
known from spinosaurids, this tetanuran sub-
clade seems to have acquiered an elongated
cranium (see Charig and Milner 1998; Sereno
et al. 1998; Martill et al. 1996) similar to, or
more incipient than that of the coelophysoids.
The present phylogenetic analysis depicted
the derived state of this character as a possible
apomorphy of Coelophysoidea under a DEL-
TRAN optimization, due to its presence in
Herrerasaurus.
(2) Rostral maxillary alveolar margin dor-
somedially oriented (Tykoski 1998). In the
majority of dinosaurs the rostral end of the
maxillary alveolar margin is almost straight
or gently upturned. In coelophysoids and
spinosaurids the rostral tip of the maxilla
is dorsomedially oriented, resulting in a rostro-
ventrally projected first maxillary tooth (Tykoski
1998). This results in a sharp curvature of
M. D. Ezcurra & F. E. Novas50
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the rostral half of the upper tooth row, that seems
to be correlated with the dorsoventrally
expanded rostral end of the dentaries and
enlarged mesial teeth of these taxa.
(3) Rostromedial process of the maxilla ros-
trocaudally long and dorsoventrally low,
well extended rostrally and fairly visible in
lateral view. Albeit partially covered by matrix,
the rostromedial process of the left maxilla of
Zupaysaurus is visible in lateral view (Figure 13).
This process, which articulates with the vomer
and premaxilla, is long, thin, and rostroventrally
oriented, as occurs in coelophysoids. In these
taxa the rostromedial process of the maxilla is
rostrocaudally lengthened, as well as dorsoven-
trally low (e.g. Coelophysis rhodesiensis,QG1;C.
bauri, CM C-3-82; Dilophosaurus, Tykoski 2005,
fig. 22A, 24A, TMM 43646-1, UCMP 37303).
In Liliensternus, only the caudal portion of the
rostromedial process is preserved. However, on
the basis of the preserved area, the rostromedial
process of the maxilla seems to be dorsoventrally
low, resembling the morphology exhibited by
coelophysids, Dilophosaurus, and Zupaysaurus.
On the other hand, in the ceratosaurian
Ceratosaurus, the rostromedial process of the
maxilla is a rostrocaudally short and dorsoven-
trally high process. Furthermore, in the abeli-
sauroid Masiakasaurus, the rostromedial process
of the maxilla seems to be slightly more
dorsoventrally extended and rostrocaudally
shortened, not extending well beyond the
maxillary alveolar border, in contrast with the
condition in Coelophysoidea. Additionally, in
the basal tetanuran Sinraptor, this process shows
a moderate length, is dorsoventrally deep
caudally, and tapers rostrally. In megalosaurids
(e.g. Poekilopleuron) the process is also low, but
shorter than in coelophysids. In Allosaurus, the
rostromedial process of the maxilla is extremely
compressed rostrocaudally, but well developed
dorsoventrally.
In sum, the rostrocaudally short and dorso-
ventrally low rostromedial process of the maxilla
of Zupaysaurus resembles the conditon present in
Lilensternus, Dilophosaurus, and the Coelophysi-
dae, differing from the dorsoventrally deep
process exhibited by averostran theropods.
In coelophysids and Dilophosaurus (Tykoski
2005), this process fits into a notch that is formed
by the subdivided caudal process of the
premaxilla, resulting in two different prongs
(Colbert 1989). This tongue and groove joint
may allow a passive kinensis between the
premaxilla-maxilla articulation, preventing its
hyperflexion (Colbert 1989; Tykoski 1998). This
specialized snout, characteristic of coelophysids,
seems to have also been present in Zupaysaurus,
as well as in Liliensternus.
(4) Maximum length of inter nal antorbital
fenestra 25% or greater than skull length
(premaxilla-quadrate condyle) (Rowe and
Gauthier 1990). The internal antorbital fenestra
was described by Arcucci and Coria (2003) as
“not as large as in the coelophysids Coelophysis
and Syntarsus, resembling in contrast the
condition present in Ceratosaurus, Carnotaurus,
Allosaurus, and more advanced tetanurans”.
However, the internal antorbital fenestra is of
large size (Figure 9), and extends for more than
35% of the skull length, a similar ratio to that of
Coelophysis bauri (Colbert 1989), C. rhodesiensis
(Raath 1977), Syntarsus (Rowe 1989), and
Dilophosaurus (Welles 1984; Rowe and Gauthier
1990). Among the Tetanurae, large antorbital
fenestrae were only convergently acquired by
Carcharodontosaurus (Tykoski 1998) and Acro-
canthosaurus.
(5) Rostral end of dentar y dorsoventrally
expanded (Gauthier 1986) and
(6) mediolateral width of rostral end of dentary
expanded (Carrano et al. 2005). In most
dinosaurs, the rostral end of the dentary gently
tapers rostrally in both dorsoventrally and
lateromedially directions. In the coelophysoids
Coelophysis bauri, C. rhodesiensis, Syntarsus,
Liliensternus, Dilophosaurus,andZupaysaurus
the rostral end of the dentary is dorsoventrally
expanded (Sereno 1999), as well as laterome-
dially widened (Carrano et al. 2005). In
addition, the apomorphic state of the character
seems to have been convergently acquired by
spinosauroid basal tetenurans (e.g. spinosaurids,
Magnosaurus; Stromer 1915; Charig and Milner
1998; Rauhut 2003).
(7) Enlarged mesial dentary teeh (fang-like)
(Gauthier 1986). Gauthier (1986), Rowe and
Gauthier (1990), and Sereno (1999) recognized
the presence of an enlarged mesial dentary tooth
(fang-like) in some basal theropodian taxa.
Sereno (1999) interpreted the presence of this
fang-like tooth as an synapomorphy of the
Coelophysoidea. Recently, Tykoski (2005)
pointed out that there is more than one enlarged
mesial dentary tooth in the rostral alveolar
margin of coelophysoids. The apomorphic state
of this feature is present in Dilophosaurus (Welles
1984), Liliensternus (von Huene 1934), Syntarsus
(Tykoski 2005), Coelophysis rhodesiensis (Raath
1977), and Zupaysaurus.Convergently,the
spinosauroids show enlarged mesial dentary
teeth. In C. bauri, albeit the mesial dentary
teeth are proportionally large (CM C-3-82), the
jaws are closed in most specimens, hampering
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the definition of the state of the character in this
taxon.
(8) Angular reaches caudal end of mandible,
blocking surangular from ventral margin of
the jaw in lateral view (Tykoski 2005). In the
majority of dinosaurs the angular is a bone that
forms most of the ventral margin of the jaw,
caudal to the dentary, with its caudal end rostral
to the retroarticular process; therefore the
surangular reaches the ventral margin of the
caudal end of the jaw. In Herrerasaurus (Sereno
and Novas 1993) Dilophosaurus (Welles 1984),
Syntarsus (Tykoski 1998, 2005), and Zupaysaurus
the angular is caudally extended up to the caudal
tip of the jaw, excluding the surangular from the
ventral margin of the mandible. Our phylogenetic
analyses exhibit the derived state of that feature
as a possible apomorphy of the Coelophysoidea
under DELTRAN optimization.
(9) Deep fossa on the craniolateral surface of the
ascending process of the astragalus .Thedistal
end of the fibula flared into a sheet of bone that
overlaps the ascending process of the astragalus was
originally proposed by Rowe and Gauthier (1990)
as a diagnostic feature of a monophyletic Cerato-
sauria, i.e.: (Coelophysoidea þ Neoceratosauria).
However, Rauhut (2003) reinterpreted the men-
tioned character as diagnostic of a subclade of
“ceratosaurs”. This author argued that this feature
is only present in articulated specimens of
Coelophysis rhodesiensis (e.g. QG 1) and Syntarsus
kayentakatae; concluding that this trait might
representaderivedfeatureonlysharedby
coelophysids, or the genus Syntarsus”(i.e.S.
kayentakatae and C. rhodesiensis).
Nevertheless, the overlapping of the bula over
the cranial surface of the ascending process of the
astragalus does not seem to be related to the
articulated nature of the specimens. On the other
hand, as was pointed out by Raath (1990) and
Colbert (1990) this individual variation depends on
the ontogenetic development of the specimen (e.g.
Raath 1990:101). In the specimens of Coelophysis
rhodesiensis where the astragalocalcaneum is not
fused to the tibia, the fibula is not ared into a sheet
of bone that overlaps the ascending process of the
astragalus. In these unfused specimens (e.g. QG
768, Raath 1990, fig. 7.9a) the craniolateral surface
of the ascending process of the astragalus, obscured
by the fibula in the “fused” individuals, exhibits a
large and deep fossa. Likewise, in Zupaysaurus,an
indentical fossa is present in the craniolateral
surface of the ascending process of the astragalus
(Figures 4A, 5A, 11G). In Liliensternus liliensterni
(HMN MB R. 2175), Dilophosaurus wetherilli
(UCMP 37303, Tykoski 2005, fig 94c), and
Syntarsus kayentakatae (MNA V2623, Tykoski
2005, g 94b), the derived state of this chracter is
also present. In Coelophysis bauri, Colbert (1989)
reported the absence of the ascending process of the
astragalus. However, as previosuly indicated by
other authors (Padian 1986), C. bauri has an
ascending process of the astragalus. Thus, Colbert’s
judgement could be the result of the distally flared
end of the fibula obscuring the ascending process of
the astragalus, as in Syntarsus and C. rhodesiensis.
Nevertheless, specimens of C. bauri with unfused
tibiotarsi also show this deep fossa on the
craniolateral surface of the ascending process of
the astragalus (TMM, Tykoski 2005, 45559-16, fig
97c). In other basal saurischians (e.g. Herrerasaurus,
Saturnalia, Plateosaurus, To r v o s a u r u s , Allosaurus,
Sinraptor) the craniolateral surface of the ascending
process of the astragalus is almost flat.
In this morphological context, during late
adulthood of coelophysids, and possibly Zupay-
saurus, Lilienternus,andDilophosaurus, the fusion of
the tarsus to the tibia, in order to form a fused
tibiotarsus, seems to have been also accompanied
by the medially flared distal end of the fibula. This
flared fibula fits in the cranioventral notch at the
base of the ascending process of the astragalus, as
occurs in the extensively fused tarsus of the large
individuals (see Rowe 1989, fig 6; and Raath 1990,
fig 7.9).
In summary, the presence of a deep and large
fossa at the craniolateral surface of the ascending
process of the astragalus seems to be an apomorphic
feature shared by Dilophosaurus, Liliensternus,
Zupaysaurus, Syntarsus, Coelophysis rhodesiensis,
and C. bauri.
Other probable apomorphic features shared by
Zupaysaurus and othe coelophysoids is a tibiofibular
crest of distal femur sharply demarcated from the
fibular condyle by a sulcus or concavity (Rowe
1989). This feature was originaly interpreted as
diagnostic of a monophyletic Ceratosauria ( ¼
Coelophysoidea þ Neoceratosauria, sensu Rowe
1989). The present phylogenetic analyses show that
this feature could constitute an apomorphy of the
Coelophysoidea under ACCTRAN optimization.
Liliensternus 1 (Zupaysaurus 1
Coelophysidae)
Furthermore, Zupaysaurus is positioned within a
lesser inclusive clade of Coelophysoidea, sharing
the following apomorphies with Liliensternus and
coelophysids (but not Dilophosaurus):
(10) Alveolar margin shar ply mediodorsally
upturned in the rostral-most tip of the
maxilla. As previously mentioned (see character
2), in most dinosaurs the rostral alveolar margin of
the maxilla is almost straight or gently dorsally
oriented. In Dilophosaurus (Welles 1984) the rostral
half of the maxillary alveolar margin is progressively
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but strongly rostromedially oriented, resulting in a
first maxillary tooth rostroventrally projected. On
theotherhandandincontrastwithDilophosaurus,
in more derived coelophysoids such as Liliensternus
(von Huene 1934), Coelophysis bauri (CM C-3-82),
Coelophysis rhodesiensis (QG 1), Syntarsus kayenta-
katae (Tykoski 1998), and Zupaysaurus the rostral
half of the maxilla is almost straight until its rostral-
most tip, which shows a sharp rostromedial
orientation of the alveolar margin. This condition
resembles to that of the Spinosauridae (e.g.
Baryonyx, Suchomimus, Spinosaurus maroccanus;
Charig and Milner 1998; Sereno et al. 1998;
Taquet and Russell 1998).
(11) Dorsoventrally compressed ridge ( 5 alveolar
ridge, sensu Rowe 1989) on the lateral surface
of the maxilla, forming the ventral border of
the antorbital fossa (Rowe and Gauthier 1990).
As was mentioned by Arcucci and Coria (2003) the
maxillary horizontal ramus of Zupaysaurus lodges a
marked longitudinal ridge (Figures 1, 9, 13). This
ridge defines the ventral margin of the antorbital
fossa, is parallel to the alveolar border, and extends
to almost the caudal tip of the horizontal process of
the maxilla. This ridge arises from the rostralmost
area of the antorbital fossa and disappears in the
caudalmost tip of the horizontal ramus of the
maxilla. This alveolar crest (sensu Rowe 1989;
Rowe and Gauthier 1990), is also present in the
coelophysoids Liliensternus (von Huene 1934),
Syntarsus (Rowe 1989), Coelophysis rhodesiensis
(Raath, 1977), and C. bauri (Colbert 1989).
Furthermore, this structure has also been reported
for the basal theropod Eoraptor (Tykoski 1998,
PVSJ 512) and the derived coelurosaurian Ornitho-
lestes (Rauhut 2003).
(12) Sublacrimal part of jugal squared rostrally
(Rauhut 2003). As was pointed out by Rauhut
(2003), the rostral process of the jugal of most
theropods is dorsoventrally expanded (e.g. Dilopho-
saurus, Sinraptor, Allosaurus). The sublacrimal
ramus of the jugal shows a squared-shaped rostral
tip in Liliensternus, Syntarsus kayentakatae (Rauhut
2003), and Coelophysis bauri (CM C-3-82); whereas
new materials show that the rostral process of
C. rhodesiensis is tapering (Bristowe and Raath
2004). In Zupaysaurus, the rostral ramus of the jugal
exhibits an overall squared rostral tip, and does not
participate in the external margin of the internal
antorbital fenestra, resembling Coelophysis and
Syntarsus. Additionally, in Ceratosaurus nasicornis
(USNM 4735) the sublacrimal process of the jugal
seems to also taper rostrally. The presence of a
rostrally tapering jugal was indicated by Rauhut
(2003) as a plesiomorphic state for dinosaurs.
(13) Space between ventral glenoid and caudo ven-
tral coracoid process ( 5 sternal process) less
than dorsoventral depth of glenoid (Carrano
et al. 2005).InLiliensternus (HMN MB R. 2175),
Coelophysis bauri (CM C-3-82), Syntarsus (Rowe
1989) and Zupaysaurus the space between the
ventral border of the glenoid fossa and the
caudoventral process of the coracoid is less than
the dorsoventral depth of the glenoid cavity
(Carrano et al. 2005). In Dilophosaurus, Coelophysis
rhodesiensis, and other neotheropods the height of
the glenoid exceeds the space between its ventral
border and the coracoid sternal process. The
apomorphic condition of a dorsoventrally low
coracoid also occurs in the basal dinosauriform
Silesaurus (Dzik 2003) and the basal sauropodo-
morph Thecodontosaurus (Yates 2003). In neothero-
podian outgroups a moderately tall coracoid is
present.
(14) Lateral malleolous of the tibia polygonal-
shaped (Sereno 1999). The distal end of the tibia
of Zupaysaurus shows a polygonal-shaped lateral
malleolus. This morphology is almost identical to
that of Liliensternus lilensterni (HMN MB R. 2175)
(Figure 11A,B). Furthermore, the coelophysoid
theropods Gojirasaurus, Coelophysis,andSyntarsus
also exhibit a polygonal postfibular wing (Sereno
1999). On the other hand, the postfibular wing of
the majority of theropods, including Herrerasaur-
idae (e.g. Herrerasaurus), Dilophosaurus,Cerato-
sauria (e.g. Masiakasaurus), and Tetanurae (e.g.
Torvosaurus, Allosaurus), despite their different
degrees of development, are all lobular, differing
from the condition present in Zupaysaurus, Lilien-
sternus, Gojirasaurus and Coelophysidae. A similar
polygonal-shaped lateral malleolus seems to be also
presentintheallosauroidtetanuranSinraptor.
(15) Astragalus fused to the calcaneum in adults
(Welles and Long 1974). The presence of an
astragalocalcaneum (fused astragalus and calca-
neum) was indicated as synapomorphic of a
monophyletic Ceratosauria (Coelophysoidea þ
Neoceratosauria) (Rowe 1989; Rowe and Gauthier
1990). An astragalus fused to the calcaneum is
present in several neotheropodian taxa including
the coelophysoids Zupaysaurus, Liliensternus, Syn-
tarsus, Coelophysis bauri, C. rhodesiensis,and
ceratosaurians (e.g. Ceratosaurus, Masiakasaurus).
No neotheropodan outgroup, or tetanuran taxa
present an astragalocalcaneum. Within the Coelo-
physoidea, the immature nature of the available
specimens of Dilophosaurus hampers the definition
of this feature in this taxon (Tykoski 1998). In this
regard, our phylogenetic analyses indicate the
presence of an astragalocalcaneum as a probable
apomorphic feature of a lesser inclusive clade of
Coelophysoidea, under DELTRAN optimization,
that includes Liliensternus, Zupaysaurus,and
coelophysids.
Phylogenetic relationships of Zupaysaurus 53
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Zupaysaurus þ Coelophysidae
Zupaysaurus also shares the following features with
the Coelophysidae:
(16) Angle betw een the rostrod orsal margin of the
maxilla and the alveolar margin less than 758.
The rostral border of the rostral process of the
maxilla is almost squared in most dinosaurs. On the
other hand, in Syntarsus (Tykoski 1998), Coelophysis
rhodesiensis (Raath 1977, QG 1), C. bauri (Colbert
1989, CM C-3-82), and Zupaysaurus the rostral
process of the maxilla taper towards the premaxilla.
This results in an angulation between the maxillary
rostrodorsal and alveolar margin of less than 758.
Among the Dinosauria, this condition has
been convergently acquiered in the spinosaurid
tetanurans (e.g. Baryonyx,CharigandMilner
1997) and the basal ornithischian Lesothosaurus
(Sereno 1991).
(17) Rostral process of maxilla equal or less than
10% of total maxillary length (Tykoski 2005).
The rostral process of the maxilla is poorly
developed, representing less than 10% of the total
length of the maxilla, in Silesaurus (Dzik 2003),
Eoraptor (Sereno et al. 1993), Carnotaurus (Bona-
parte et al. 1990), and the coelophysoids Syntarsus
kayentakatae (Tykoski 1998), Coelophysis rhodesien-
sis (QG), C. bauri (CM C-3-82) (Tykoski 2005),
and Zupaysaurus.InHerrerasaurus (Sereno and
Novas 1993), basal sauropodomorphs (e.g. Theco-
dontosaurus, Plateosaurus), and several averostran
theropods (e.g. Ceratosaurus, Allosaurus, Sinraptor,
Acrocanthosaurus) the rostral process of the maxilla
is offseted from the ascending ramus, and well
developed. In Dilophosaurus andspinosauroidtaxa
(e.g. Torvosaurus, Eustreptospondylus, Baryonyx,
Suchomimus) the rostral process of the maxilla is
strongly developed, representing more than 25% of
the total length of the maxilla. Our phylogenetic
analyses indicate that a reduced rostral process of
the maxilla (less than 10% of the total length of the
maxilla) could be a probable apomorphic feature
that characterizes a lesser inclusive clade within the
Coelophysoidea, i.e.: (Zupaysaurus þ Coelo-
physidae) under DELTRAN optimization, given
the inconclusive condition of Liliensternus and the
apomorphic state exhibited by the basal theropod
Eoraptor.
(18) Antorbital fossa rostral margin square-
shaped (Rauhut 2003).InZupaysaurus,the
antorbital fossa presents a square-shaped rostral
margin, forming an acute angle with the horizontal
ramus and a wide angle with the dorsal process
(Figures 1, 9). This morphology is also present in
Coelophysis bauri, C. rhodesiensis,andSyntarsus
kayentakatae (Rauhut 2003). Interestingly, this
feature is also seen in Eoraptor (Rauhut 2003).
A square-shaped rostral corner of the antorbital
fossa is furthermore present in Noasaurus,butthe
angle between the horizontal margin and the
ascending ramus is wide in this abelisauroid, in
contrast with coelophysids, Eoraptor,andalso
Zupaysaurus.
In contrast, in Herrerasaurus, Dilophosaurus,
most ceratosaurians, and tetanurans the rostral
margin of the antorbital fossa shows a triangular or
rounded outline, resulting in a prominent acute
angle between both maxillary rami. Furthermore,
in these theropods, the ventral margin of the rostral
portion of the antorbital fossa rises continuously
upwards, resulting in the mentioned triangular
shape and acute rostral margin. On the other hand,
the rostral portion of the antorbital fossa of
Zupaysaurus and Coelophysidae presents a con-
tinuous, straight ventral margin, parallel to the
maxillary alvoelar border. In this context, the
square-shaped rostral margin of Zupaysaurus,
coelophysids and Eoraptor seems to be a conse-
quence of the straight vental margin of the
antorbital fossa.
(19) More than 18 maxill ary teeth in adults.The
high number of maxillary teeth of Zupaysaurus has
been previously pointed out by Arcucci and Coria
(2003), indicating that this taxon may have at least
23 or 24 teeth in the maxilla. This number of
maxillary teeth resembles the tooth count present in
adult coelophysid theropods, for example Coelo-
physis bauri (2226 teeth, Colbert 1989) and
Syntarsus (20, Tykoski 1998) (Figure 9). In
contrast, in Herrerasaurus (16, Sereno and Novas
1993), Dilophosaurus (12 14, Welles 1984; Tykoski
2005), Ceratosauria (e.g. Ceratosaurus (15), Carno-
taurus (12); Madsen and Welles 2000; Bonaparte
et al. 1990), and most Tetanurae (e.g. Sinraptor
(15), Monolophosaurus (13), Allosaurus (1416);
Currie and Zhao 1993; Zhao and Currie 1993;
Madsen 1976) the maxilla has a relatively low tooth
count in comparison to the Coelophysidae and
Zupaysaurus. Additionally, a high number of
maxillary teeth has been convergently acquiered
by the spinosaurid tetanurans (e.g. Suchomimus
(22), Sereno et al. 1998) and the highly derived
troodontids (Russell and Dong 1993).
(20) Pronounced lateral rims of the nasals and
dorsolateral margins of lacrimal forming a
low and laterally projected pair of ridges
(Rauhut 2003). As reported by Rauhut (2003,
character 22), in Coelophysis bauri, C. rhodesiensis,
Allosaurus, and sinraptorids, the lateral rims of the
nasals are exposed over the maxillae forming a pair
of parasagital ridges, whereas in most other
archosaurs the skull profile is transversely rounded
above the nasals. These ridges are rostrally
projected from the horizontal ridge of the lacrimal,
which delimits the dorsal border of the lacrimal
M. D. Ezcurra & F. E. Novas54
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antorbital fossa. This condition is also present in
Zupaysaurus.InSyntarsus kayentakatae,ifthepairof
vertical crests on the skull roof are re-interpreted as
displaced nasals (Ezcurra and Novas 2005), the
condition reported for Coelophysis and Zupaysaurus
seems to be also present. The present phylogenetic
analyses indicate the presence of low parasagital
ridges as a probable apomorphy of a node that
enclose Zupaysaurus and the Coelophysidae, under
DELTRAN optimization.
(21) Lacrimal rostral ramus longer tha n the
ventral ramus (Tykoski and Rowe 2004).The
horizontal ramus of the lacrimal of Zupaysaurus
exhibits a moderate low and rostrally downturned
blade. Its rostralmost tip is tapering, associated with
a forked caudal articular area of the ascending
process of the maxilla, a condition that resembles
the pattern of some tetanurans. Furthermore, the
horizontal lacrimal ramus of Zupaysaurus is well
developed rostrally, showing a greater length than
the ventral process (Figures 1, 9), a character that
was previously considered as autapomorphic of the
genus by Arcucci and Coria (2003). However, in
Coelophysidae (e.g. Syntarsus, Coelophysis rhode-
siensis, C. bauri; Tykoski and Rowe 2004) the
horizontal ramus of the lacrimal is also well
extended rostrocaudally. In Dilophosaurus,the
length of the horizontal ramus of the lacrimal is
unclear, but this ramus is higly modified from the
general condition of coelophysoid theropods.
On the other hand, in all other theropods
(e.g. Herrerasaurus, Ceratosaurus, Sinraptor, Poekilo-
pleuron, Allosaurus) the length of the rostral ramus of
the lacrimal does not exceed the height of the ventral
ramus.
The unknown lengths of the horizontal process
of the lacrimals of Dilophosaurus and Liliensternus
suggest that this feature could be more widely
distributed within the Coelophysoidea.
(22) Infratemporal fenestra strongly rostrocaud-
ally compressed, which maximum length
versus maximum length of the orbit ratio
less than 0.8. The infratemporal fenestra is
strongly rostrocaudally compressed in coelophysid
coelophysoids (e.g. Coelophysis, Syntarsus). Furthe-
more, as pointed out by Arcucci and Coria (2003),
the infratemporal fenestra of Zupaysaurus is key-
hole-shaped, with both proximal and distal
sectors sagitally expanded, but also strongly
rostrocaudally compressed at mid-height, resem-
bling the coelophysid pattern (Figures 1, 9).
In Liliensternus, the preserved jugal indicates an
infratemporal fenestra subequal in width with the
orbit (Rauhut pers. comm.).
In contrast, in Herrerasaurus, Ceratosauria
(Ceratosaurus, Abelisaurus, Carnotaurus, Majun-
gatholus), and Sinraptor (Currie and Zhao 1993,
fig 3B) the infratemporal fenestra is a rostro-
caudally wide opening and nearly subrectangular
in shape. Furthermore, tetanurans (e.g. Mono-
lophosaurus, Allosaurus)andDilophosaurus also
present a keyhole-shaped infratemporal fenestra
but this opening is more rostrocaudally extended
when compared with coelophysids and Zupay-
saurus.
(23) Squamosalcaudalprocessstronglycaudally
extended and longer than the rostral pro-
cess, sometimes exceeding the caudal level
of the quadrate condyle in lateral view.In
most dinosaurs, the caudal process of the
squamosal is shorter than the rostral, and does
not exceed the caudal level of the quadrate
condyle. In the coelophysoids Zupaysaurus,
Syntarsus kayentakatae (Tykoski 1998), Coelophysis
bauri (Colbert 1989, CM C-3-82), and C.
rhodesiensis (Raath 1977), the caudal process of
the squamosal is well extended sagitally, longer
than the squamosal rostral process, and posi-
tioned caudal to the level of the quadrate condyle
in lateral view. Among other coelophysoids,
Dilophosaurus show the plesiomorphic condition,
and in Liliensternus the state of the character is
uncertain. In this context, the present cladistic
analyses show that the apomorphic condition of
this feature is a probably apomorphy of a clade
that includes Zupaysaurus and the Coelophysidae,
under DELTRAN optimization, whereas the
ACCTRAN optimization interprets the apo-
morphic state as shared by coelophysoids more
derived than Dilophosaurus.
(24) Caudal curvature of the dorsal end of
quadrate, with quadrate head caudodorsally
oriented. In the basal dinosauriform Silesaurus
(Dzik 2003) and most saurischian dinosaurs
(including the coelophysoids Dilophosaurus and
Liliensternus) the quadrate head is aligned with
the main axis of the bone. In Zupaysaurus,
Syntarsus kayentakatae, Coelophysis rhodesiensis,
and C. bauri the quadrate head is caudodorsally
oriented, due to the caudal curvature of the
dorsal end of the bone. Since this feature seems
to ally Zupaysaurus and the Coelophysidae, its
presence was interpreted in our phylogenetic
analyses as convergently acquired by these
coelophysoids, basal ornithischians (e.g. Lesotho-
saurus, Heterodontosaurus), Eoraptor,andCarno-
taurus.
Moreover, Zupaysaurus resembles other coelophy-
soid taxa in the presence of the following derived
features:
Rostral-most tip of rostral process of jugal with
three disti nct prongs (Ezcurra and Novas 2005).
In Zupaysaurus the rostral process of the jugal presents
Phylogenetic relationships of Zupaysaurus 55
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three distinct prongs, a morphology almost identical to
that of Syntarsus kayentakatae (Figure 14), which has a
very similar distribution of prongs and articulation
with the lacrimal and maxilla. This morphology is the
result of a marked longitudinally forked rostral
process of the jugal and the presence of a small third
and dorsally projected prong. In Liliensternus (von
Huene 1934, fig 5), Coelophysis rhodesiensis (Bristowe
and Raath 2004), C. bauri (CM C-3-82), and
coelophysoid outgroups, these small rod-like prongs
are absent.
The dorsally projected prong of Zupaysaurus and
Syntarsus kayentakatae could be homologized with the
dorsal projection of the rostral process of the jugal of
Dilophosaurus and more derived theropods such as
Ceratosaurus, Monolophosaurus, and Sinraptor. In these
taxa, the dorsal projection overlaps the caudoventral
corner of the vertical ramus of the lacrimal (as is
the case, in a lesser degree, in Zupaysaurus and
S. kayentakatae), whereas a single rostral prong tapers
rostrally. In this regard, the small-sized dorsal prong
exhibited by Zupaysaurus and S. kayentakatae could
represent an intermidiate state between the dinosaur-
ian plesiomorphic condition of a tapering rostral
process, and the trait reported for Dilophosaurus and
the Averostra.
The three-pronged condition, with a subdivided
rostral tip of the sublacrimal ramus of the jugal, seems
to be a feature shared only by Zupaysaurus and
Syntarsus kayentakatae. Due to its absence in
Dilophosaurus and Liliensternus, the present phyloge-
netic analyses suggest the three-pronged condition as
a probable apomorphy of the node that includes
Zupaysaurus and the Coelophysidae, under ACC-
TRAN optimization.
Postorbital excluded from the supratemporal
fossa (Sereno 1999). Zupaysaurus and Coelophysis
exhibit the apomorphic condition of a postorbital that
does not participate in the supratemporal fossa
(Sereno 1999) (Figure 9). In contrast, in all other
theropods the postorbital delimits the rostrolateral
region of this fossa.
Slightly marked tuberosity cranial to the
glenoid fossa. In Zupaysaurus a slightly marked
tuberosity is present on the lateral surface of the
proximal end of the scapula, near to its suture with the
coracoid, and cranial to the glenoid fossa. A similar
tuberosity is present at least in Coelophysis rhodesiensis
(QG 1), and probably also in C. bauri (CM C-3-82).
In Liliensternus (HMN MB R. 2175) this tuberosity is
absent. In Dilophosaurus, Gojirasaurus,andmost
coelophysoid outgroups, the presence of this tuberos-
ity has not been reported.
Nevertheless, Zupaysaurus is not a member of
Coelophysidae because of the absence of the following
coelophysid unambiguous apomorphies: a longitudi-
nal ridge on the lateral surface of the jugal, circular
orbit, ventral border of the infratemporal fenestra
mostly constituted by the quadratojugal, dorsal ramus
of the quadratojugal longer than the rostral ramus,
mediolateral width of anterior end of dentary equal to
that of caudal part, and caudoventral process of the
coracoid tapering and projected beyond the caudal
margin of the glenoid fossa.
In this context, the features shared by Zupaysaurus
and coelophysids are here interpreted as diagnostic of a
lesser inclusive ingroup of Coelophysoidea. In
addition, some cranial features previously considered
to diagnose Coelophysidae (e.g. squared rostral
margin of the maxillary antorbital fossa, pronounced
lateral rims of the nasals, supratemporal fossa excluded
from the postorbital; inconclusive in the basal
coelophysoid Liliensternus) are actually more wide-
spread within the Coelophysoidea, since they occur in
the non-coelophysid coelophysoid Zupaysaurus.
Plesiomorphic non-tetanuran characters retained by
Zupaysaurus
In congruence with the features mentioned before,
supporting the allocation of Zupaysaurus with the
Coelophysoidea and not with the Tetanurae, the
Argentine taxon retained several plesiomorphic fea-
tures present in Coelophysoidea, but absent in more
derived ceratosaurians and tetanurans. Some of these
plesiomorphic traits include: maxillary tooth row
behind the internal antorbital fenestra, jugal lateral
surface apneumatic, prefrontal widely exposed on the
rostrodorsal rim of the orbit in lateral view, frontal
rostrocaudally elongated, rostral process of the
postorbital strongly rostrodorsally oriented, ventral
rim of the bases of the paroccipital processes above or
level with the dorsal border of the occipital condyle,
blade-like and craniocaudally extended axial neural
spine, tibiofibular crest exhibiting its main axis
caudolaterally oriented, with a convex surface on its
medial margin, absence of a cranial groove on the
distal end of femur, caudolateral extension of lateral
malleolus of the distal tibia only partially overlapping
the distal end of fibula and calcaneum, distal end of
the tibia squared and with small lateral process in
distal view, facet on distal tibia for the reception of the
ascending process of the astragalus subtriangular and
well developed cranially, craniomedial corner of the
distal tibia rounded, astragalus fused to calcaneum,
low astragalar condyles, low ascending process of the
astragalus, wide proximal articular surface of the
astragalar ascending process, and calcaneum without
facet for tibia.
Conclusions
The assignation of Zupaysaurus rougieri to the Coelo-
physoidea constitute the first evidence of this super-
family of basal neotheropods in South America. The
discovery of Zupaysaurus is in accord with the global
M. D. Ezcurra & F. E. Novas56
Downloaded By: [Ezcurra, Martín Daniel] At: 16:18 23 February 2011
fossil record, in which Triassic theropod dinosaurs are
mainly represented by coelophysoids and herrerasaur-
ids. Furthermore, the reassignation of Zupaysaurus to
the Coelophysoidea, as well as the recent description of
coelophysoid materials from China (Irmis 2004),
increase the paleobiogeographical range of this super-
family during the late Triassic early Jurassic, and
supports a global distribution of this lineage.
The preservation of the almost complete skull of
Zupaysaurus allowed us to understand crucial aspects
of the cranial anatomy of the basal taxa belonging to
the Coelophysoidea. The new anatomical information
provided by Zupaysaurus reveals that characters
previously interpreted as synapomorphic of the
Coelophysidae (e.g. rostral margin of maxillary
antorbital fossa squared, absence of postorbital
participation in supratemporal fossa) (Sereno 1999;
Rauhut 2003) were also present in more basal
members of the clade, and were not only restricted
to the Coelophysidae (i.e. Coelophysis and Syntarsus).
Acknowledgements
We want to thank Sergio Martin (PULR) for allowing
access to the holotype specimen of Z. rougieri under his
care. The authors also want to thank Max Langer and
the reviewers Matthew Carrano and Oliver Rauhut for
their comments which improved the qualitity of the
manuscript.
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