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A new theropod Abelisauridae is described, Ekrixinatosaurustinis novasi gen. et sp. nov., of northwestern Patagonia (Neuquén Province, Argentina). A preliminar cladistic analysis placed Ekrixinatosaurus together with Majungatholus and Carnotaurini; and the sister group is Ilokelesia. The presence of this specimen in Albian-Cenomarúan beds allows us to support the early divergence (pre-Senonian) of this clade, and the hypothesis of the presence of Abelisauridae in continental Africa. The present distribution of Abelisauridae indicates: 1) a vicariance of this clade based on a pre-Cenomanian pan-Gondwanic distribution; 2) dispersion throughout terrestrial bridges. In both cases, the absence of Abelisauridae in continental Africa can be considered a bias of the fossil record.
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Abelisauridae a family of big Gondwanic preda-
tors very abundant during the Late Cretaceous. Both
in diversity and in numbers of specimens,
abelisaurids are the best documented theropod di-
nosaurs in South America (Novas, 1997). However,
most of these fossils are known only from isolated
fragmentary bones or partial skeletons. Until now,
Carnotaurus sastrei (Bonaparte, 1985; Bonaparte et al.,
1990) and Aucasaurus garridoi (Coria et al., 2002) are
the most complete specimens of the family Abelisau-
ridae. We describe a new Abelisauridae theropod,
Ekrixinatosaurus novasi gen. et sp. nov. based on a
partial skeleton found disarticulated and dispersed
over 15 m2. The present anatomical description fo-
cuses on the most novel information preserved in
Ekrixinatosaurus novasi, including portions of the
skeleton that are unknown, unpublished, or poorly
preserved in other abelisaurs. The discovery oc-
curred due to excavations for building a gas pipeline
(Gasoducto del Pacífico Company) in Bajo del Añelo
(figure 1), Neuquén Province, Argentina.
The known distribution of Abelisauridae mem-
bers in South America, Madagascar and India have
allowed to evaluate the hypothesis of a dispersion
route between South America and the Indo -
Madagascar plate through Antarctica by a terrestrial
bridge (Kerguelen Plateau) during the late
Cretaceous (Sampson et al., 1998). This hypothesis is
based on a divergence of the clade, posterior to the
separation of Africa and South America. However,
the recent report of an Abelisauridae maxilar in
Cenonian-Turonian beds has changed the diver-
gence of this clade toward the same continental
break (Lamanna et al. 2002). According to these au-
thors, this finding may show a pan-Gondwanic dis-
tribution of this family.
Abbreviation. MUCPv, Museo Universidad
Nacional del Comahue, Paleovertebrados, Neu-
1Centro Paleontológico Lago Barreales, Universidad Nacional del
Comahue, Ruta Provincial 51, kilómetro 65. Neuquén, Argentina.
2Universidad de Chile, Laboratorio de Zoología de Vertebrados,
Facultad de Ciencias. Las Palmeras 3425, Santiago, Chile.
3Museo Nacional de Historia Natural, Sección Paleontología.
Casilla 787, Santiago, Chile.
4Universidad Austral de Chile, Instituto de Geociencias. Casilla
567, Valdivia, Chile.
A new Abelisauridae (Dinosauria: Theropoda)
from northwest Patagonia
Jorge O. CALVO1, David RUBILAR-ROGERS2,3 and Karen MORENO4
Key words. Dinosauria. Abelisauridae. Systematic. Phylogeny. Patagonia.
Palabras clave. Dinosauria. Abelisauridae, Sistemática. Filogenia. Patagonia.
Abstract. A new theropod Abelisauridae is described, Ekrixinatosaurus novasi gen. et sp. nov., of north-
western Patagonia (Neuquén Province, Argentina). A preliminar cladistic analysis placed Ekrixinatosaurus
together with Majungatholus and Carnotaurini; and the sister group is Ilokelesia. The presence of this spec-
imen in Albian-Cenomanian beds allows us to support the early divergence (pre-Senonian) of this clade,
and the hypothesis of the presence of Abelisauridae in continental Africa. The present distribution of
Abelisauridae indicates: 1) a vicariance of this clade based on a pre-Cenomanian pan-Gondwanic distrib-
ution; 2) dispersion throughout terrestrial bridges. In both cases, the absence of Abelisauridae in conti-
nental Africa can be considered a bias of the fossil record.
un nuevo terópodo Abelisauridae, Ekrixinatosaurus novasi gen. et sp. nov., del noroeste de la Patagonia
(provincia del Neuquén, Argentina). Un análisis cladístico preliminar ubica a Ekrixinatosaurus en un nodo
junto a Majungatholus y Carnotaurini; y a Ilokelesia como grupo hermano. La presencia de este espécimen
en capas del Albiano-Cenomaniano permite sustentar la divergencia temprana (pre-Senoniana) de este
clado y la hipótesis de la presencia en Africa continental de Abelisauridae. La presente distribución de
Abelisauridae puede reflejar: 1) una vicarianza de este clado a partir de una distribución pan-Gondwánica
pre-Cenomaniana; 2) dispersión a través de puentes terrestres. En ambos casos, la ausencia de Abelisau-
ridae en África continental puede considerarse un sesgo del registro fósil.
AMEGHINIANA (Rev. Asoc. Paleontol. Argent.) - 41 (4): 555-563. Buenos Aires, 30-12-2004 ISSN 0002-7014
©Asociación Paleontológica Argentina AMGHB2-0002-7014/04$00.00+.50
J.O. Calvo, D. Rubilar-Rogers and K. Moreno
Systematic paleontology
THEROPODA Marsh, 1881
ABELISAURIDAE Bonaparte and Novas 1985
Ekrixinatosaurus gen. nov.
Type species. Ekrixinatosaurus novasi sp. nov.
Etymology. From the Greek Ekrixi, meaning “explo-
sion”; the Latin nato, meaning “born”, referred to the
fact that the fossil was discovered after its rocky
tomb was dynamited; and the Greek saurus, meaning
“reptile” or “lizard”.
Diagnosis. As for the species.
Ekrixinatosaurus novasi sp. nov.
(Figures 2, 3, 4, 5, 6, 7, 8)
Holotype. MUCPv-294, a well preserved disarticu-
lated skeleton with elements including: left and par-
tial right maxillae; basicranium; both dentaries; teeth;
cervical, a dorsal, sacral and caudal vertebrae;
haemal arches; ribs; ilia, pubis and proximal ischia;
left and distal end of right femur; left tibia; left astra-
galus and calcaneum; proximal end of left fibula and
right tibia; metatarsals; phalanges; and a pedal un-
Etymology. novasi, in honor of Dr. Fernando Novas
for his important contributions to the study of
abelisaurid theropods.
Diagnosis. Ekrixinatosaurus novasi is a large abelisaur
theropod, between 7 to 8 m of total length, distin-
guished by the following characters: presence of a
fenestra between the postorbital and the anterior bor-
der of the frontal; protuberance directed backward on
the contact between the parietals with the paraoccipi-
tal process. Cervical vertebrae cranio-caudally com-
pressed; cervical neural spines as tall as the epipophy-
ses; mid-posterior cervical centrum with ventral side
flattened; two wide foramina in the mid-posterior cer-
vicals; small preespinal depression with a pneumatic
excavation connected to the neural canal in the mid-
dle-posterior cervicals; small pre-spinal lamina in
mid-cervicals; tibia with a swelling at midshaft.
Locality. Approximately 34 km northwest of Añelo,
Neuquén Province, northwestern Patagonia,
Argentina (figure 1).
AMEGHINIANA 41 (4), 2004
Figure 1. Map of Neuquén Province (northwest Patagonia) show-
ing where Ekrixinatosaurus novasi was found / Mapa de la provincia
del Neuquén (noroeste de la Patagonia) mostrando la localidad de hallaz-
go de Ekrixinatosaurus novasi.
Figure 2. Skeletal reconstruction of Ekrixinatosaurus novasi gen. et sp. nov. Scale bar 1 m / Reconstrucción del esqueleto de Ekrixinatosaurus
novasi gen. et sp. nov. Escala 1 m.
A new theropod dinosaur from Patagonia 557
Horizon. The material comes from red beds belong-
ing to the Candeleros Formation, Río Limay Group,
Albian-Cenomanian (“Middle” Cretaceous) (Calvo,
1999). The Candeleros Formation has surrendered an
assemblage of vertebrate remains: the theropod
Giganotosaurus (Coria and Salgado, 1995), the sau-
ropods Rebbachisaurus and Andesaurus as well as
some titanosaurid remains, the crocodile Araripe-
suchus, a pipid frog, fragments of turtles, pterosaur
tracks and a wide variety of dinosaur trackways
(Calvo, 1991, 1999).
The supraoccipital has a prominent posterior pro-
jection. The occipital crest is a relatively thin bone
composed of the parietals and part of the squamosal.
In posterior view the crest is convex and the parietal
is horizontal. The paraoccipital process is not com-
plete distally; however, it is subtriangular and direct-
ed ventroposteriorly. The occipital condyle and ba-
sioccipitals are missing. The parietals are fused to the
frontals. There is a protuberance directed backward
on the contact between the parietals with the paraoc-
cipital process. The frontal is a wedge-shaped block
with a flat dorsal surface. The median suture is fused
and is a straight line. The anterior portion of the
frontal is missing. The contact between frontal and
postorbital is fused. Both participate on the anterior
border of the supratemporal fenestra. The postorbital
is incomplete, just its dorsal portion is preserved and
part of the ventral process. The postorbital has a ro-
bust anterior projection that produces a fenestra be-
tween the postorbital and the anterior border of the
frontal. The squamosal is small and triradiate. The
anterior ramus is covered by the posterior projection
of the postorbital. It is not possible to see if the
squamosal participates in the supratemporal fenes-
tra. The ventral projection has a subtriangular sec-
tion. The posteroventral projection is small. The
parasphenoid is a medial ossification that is widely
fused to the ventral faces of the frontals. Ventrally
this ossification is laminar.
The maxilla is short (42 cm long) and high, with
one dorsoventrally elongated maxillary fenestra lo-
cated near the anterior border of the preorbital open-
ing (figure 3). There are 16 alveoli, some with teeth.
They are flattened laterally with anterior and posteri-
or serrations.
Mandible. The dentary is short with a convex ventral
border (figure 4). It is low and elongated anteropos-
teriorly. In lateral view it is curved with its distal end
rounded. In medial view, the Meckelian groove is
shallow anteriorly, becoming deeper and wider pos-
teriorly. It extends near the lower border of the den-
tary. The posterior third of the dentary is vertically
expanded. The interdental plates occupy half of the
lingual surface from the first alveoli to the seventh,
then becomes smaller posteriorly.
Postcranial skeleton
Vertebral column
Presacral vertebrae. Few presacral vertebrae are pre-
served in the holotype specimen MUCPv-294. There
is a small, poorly preserved anterior cervical. The
neural arch is partially preserved, just a small distal
portion of the diapophysis and is directed backward.
The centrum is opisthocoelous and longer than wide.
In lateral view, the anterior face of the centrum
makes a sharp angle with the anteroposterior plane,
indicating the limits of the dorsoventral flexion of
the neck. There are two small pleurocoels on the lat-
eral side of the centrum (figure 5). The parapophysis
is well developed. In ventral view there is a promi-
nent hypapophysis that extends from the middle of
the centra to the anterior border. In posterior view a
large cavity that leads into the neural arch is exposed.
There is a complete mid-posterior cervical verte-
brae (figure 5). The neural spine is low and broad,
barely surpassing the level of the epipophysis. The
neural arch has a small preespinal lamina, and small
prespinal depressions. The epipophysis are well de-
veloped, posterolaterally oriented and with no cra-
nial projections. In lateral view the diapophyseal
lamina is reduced. The parapophysis are well devel-
oped. In anterior view the neural arch has two big
pneumatic cavities above the neural channel. There is
AMEGHINIANA 41 (4), 2004
Figure 3. Ekrixinatosaurus novasi, left maxilla showing the ascen-
dant subvertical ramus. Scale bar 10 cm / Maxilar izquierdo
mostrando la rama ascendente subvertical. Escala 10 cm.
J.O. Calvo, D. Rubilar-Rogers and K. Moreno
a centroprezygapophyseal lamina that surrounds an-
teriorly a lateral depression. The postzygapophyses
are large and directed obliquely and ventrally. In
posterior view the wide depression behind the neur-
al spine has two rather large fenestrae that lead into
the neural arch.
A dorsal centrum is known and it is am-
phiplatyan. In anterior view, the articular face is cir-
cular and it is bigger than the posterior one. In later-
al view there is a depression with a small pleurocoel
placed anteriorly. The lateral side is convex
dorsoventrally and concave anteroposteriorly.
Caudal vertebrae. Anterior caudal vertebra are large
and robusts. The centra are amphicoelous. The later-
al surface of the centra shows a slight depression.
The ventral face of the transverse processes has a
strong ridge that extends from the anterior portion of
the centra to the distal end of the transverse process.
In lateral view, the distal end of the transverse
process extends beyond the posterior face of the cen-
tra. The thin laminar neural spine is directed back-
ward. Middle and posterior caudals are also amph-
icoelous and their centra are longer than high. The
transverse processes are directed backward and
slightly upward. Middle caudals present fore and aft
process on the distal end of the transverse processes
(figure 6). Posteriorly, the caudals have horizontal
transverse processes. The neural spine, placed poste-
riorly, is high, laterally compressed and directed
backward. Both postzygapophyses and prezy-
gapophyses are well developed.
The left femur is complete (figure 7). The diaphy-
sis is almost straight in posterior view, but in lateral
view is slightly sigmoidal. The head is directed an-
teromedially at 45º with respect to the femur axis.
The head is hemispherical, with the articular surface
smooth. The anterior trochanter, partially preserved,
projects anteriorly. The fourth trochanter is robust
and prominent; its crest is directed posteromedially.
At the distal end the condyles project posteriorly.
The internal tibial condyle is larger and it is com-
pressed laterally as are the external tibial and the
fibular. The external tibial condyle is small. In medi-
al view, at the distal end, there is a strong ridge that
clearly separates the medial and anterior faces.
Tibia, astragalus and calcaneum. These three bones are
fused. The left tibia (69 cm) is shorter and more slen-
der than the femur. In anterior view the diaphysis is
straight. The distal end is twisted 90º with respect to
the proximal one. The cnemial crest is well devel-
oped, its internal border is convex and the external
one is concave. The articulation for the femur has a
lateral articular condyle bordered in posterior view
by a sulcus. Distally the tibia is wider in order to ac-
commodate the fused astragalus and calcaneum (fig-
ure 8). A suture is seen between the tibia and astra-
galus-calcaneum in anterior view, but none between
astragalus and calcaneum. The ascending process of
the astragalus is small (6 cm).
AMEGHINIANA 41 (4), 2004
Figure 4. Ekrixinatosaurus novasi, left dentary with the convex ven-
tral border. Scale bar 10 cm / dentario izquierdo con el borde ventral
convexo. Escala 10 cm.
Figure 5. Ekrixinatosaurus novasi, mid-posterior cervical vertebra
(in anterior view) showing the hypertrophied epipophyses and
the height of the neural spine / cervical media-posterior (en vista an-
terior) mostrando la epitrofisis hipertrofiada y la altura de la espina neu-
A new theropod dinosaur from Patagonia 559
Discussion and comparisons
The skull is estimated to be ~ 83 cm long based on
comparison with Carnotaurus and Majungatholus
(Bonaparte et al., 1990; Sampson et al., 1998).
Unfortunately, Abelisaurus does not have a complete
maxilla but its preserved size is similar to
Ekrixinatosaurus. On the other hand, the femoral
length of Ekrixinatosaurus is 77 cm (figure 7), where-
as that of Carnotaurus was estimated to be 103 cm.
The Ekrixinatosaurus skull / femur length ratio is es-
timated to be 1.08 whereas in Carnotaurus it is be-
lieved to have been about 0.58 and Ceratosaurus =
1.00. Ekrixinatosaurus possesses a robust maxilla,
with a subvertical ascending process and fused inter-
dental plates, as in other members of Abelisauria.
Based on the shape of the ascending process of the
maxilla the preorbital opening is higher than long,
similar to that present in Carnotaurus. The dentary is
short with a convex ventral border as in other
Abelisauridae and Ceratosaurus (figure 4). In the bas-
icranium the supraoocipital has a prominent posteri-
or projection as in Carnotaurus. The protuberance di-
rected backward from the contact between the pari-
etals with the paraoccipital process is an autapomor-
phy of Ekrixinatosaurus. The postorbital has an ante-
rior robust projection that produces a fenestra be-
tween the postorbital and the anterior border of the
frontal, this condition is not present in other mem-
bers of the Abelisauridae (character present here as
autapomorphy). A lateral projection of the postor-
bital is present as in Abelisaurus.
Ekrixinatosaurus has hypertrophied epipophyses
and deep postspinal depressions as in Abelisauria
(Novas, 1992). Unlike Carnotaurus, the posterior face
of each anterior cervical centrum is strongly concave
while the anterior surface is almost flat. In the mid-
posterior cervicals the neural arch is relatively high
with anteroposteriorly compressed neural spine,
which is different than Ilokelesia (Coria and Salgado,
1998). Like in Carnotaurus, Noasaurus, Ilokelesia and
Aucasaurus there is a lamina that connects the
epipophysis with the prezygapophysis that separates
the dorsal surface of the neural arch from the lateral
surface. Ilokelesia has an autapomorphy, cervical ver-
tebrae with poorly defined diapopostzygapofiseal
laminae. This character is also present in Ekrixi-
natosaurus. It is probably a synapomorphy for Abe-
The anterior dorsal vertebrae are amphiplatyan. It
shares with Carnotaurus the presence of pleurocoels
in dorsals; this character is not present in Ilokelesia.
All preserved sacrals are fused to the sacral ribs
and to the ilium as in adult Ceratosauria.
On caudal vertebrae the posterolaterally project-
ing transverse processes are inclined slightly dorsal-
ly, which is different than Ilokelesia where they are
perpendicular to the dorsoventral axis of the verte-
bra, and to Carnotaurus where they are strongly in-
clined upward. Anterior caudals show wide trans-
verse processes that are cranially expanded at the
AMEGHINIANA 41 (4), 2004
Figure 7. Ekrixinatosaurus novasi, left femur in lateral view. Scale
bar 10 cm / fémur izquierdo en vista lateral. Escala 10 cm.
Figure 6. Ekrixinatosaurus novasi, mid-caudal in dorsal view show-
ing the antero-posteriorly expanded distal end of the transverse
processes. Scale bar 10 cm / vértebra media-caudal en vista dorsal
mostrando la expansión distal del proceso transverso. Escala 10 cm.
J.O. Calvo, D. Rubilar-Rogers and K. Moreno
distal end as in Carnotaurus (figure 6). In Ekrixi-
natosaurus the transverse processes are directed
slightly upward and backward. The ventral side of
each transverse process has a strong ridge along all
its length. Ekrixinatosaurus is the first abelisaurid
with posterior caudals that are known. These are am-
phicoelous and have laterally flattened subtriangular
neural spines. As in Carnotaurus the distal end of the
transverse process is expanded having a process di-
rected anteriorly. Ekrixinatosaurus shares with
Ilokelesia the fore and aft process on the distal end of
the transverse processes in middle caudals: this char-
acter was defined as autapomorphic for Ilokelesia.
However, we consider this character as a synapo-
morphy of the Abelisauridae. The distal edge of the
caudal transverse processes is slightly concave in the
middle in Ilokelesia and Ekrixinatosaurus. It has been
considered an autapomorphy of Ilokelesia, but we in-
terpret it as a synapomorphy of Abelisauridae.
The length of the ilium is close to that of the femur
as in other members of the Neoceratosauria.As in all
Ceratosauria the tibia, astragalous and calcaneous
are fused.
Phylogenetic relationships
The phylogenetic relationships between Ekrixi-
natosaurus and the most complete members of
Abelisauridae were evaluated in a preliminary
cladistic analysis using some diagnostic characters
(see appendix). Ekrixinatosaurus is more closely relat-
ed to Carnotaurini (Coria et al., 2002) than to
Neoceratosauria. Thirteen binary characters were
used. The matrix was analyzed using PAUP 4.0*b10
(Swofford, 2000) under heuristic search, and charac-
ter-state transformations were evaluated under AC-
CTRAN optimization. This analysis produced two
most parsimonious trees with a Tree Length of 14,
Consistency Index of 0.9286 and Retention Index of
0.9375 (figure 9.A). Strict consensus tree generates a
politomy among Majungatholus, Ekrixinatosaurus and
Carnotaurini; however, Ilokelesia is placed as the sister
group (figure 9.B).
Phylogenetic studies place abelisaurids within a
big subdivision of Theropoda, the Ceratosauria
(Gauthier, 1986; Rowe and Gauthier, 1990; Novas,
1991; Holtz, 1994). At least two principal groups are
recognized within Ceratosauria: Coelophysoidea,
(Upper Triassic and Lower Jurassic) which includes
Coelophysis (Cope, 1889), Syntarsus (Raath, 1969) and
Dilophosaurus (Welles, 1984) from North America,
Europe and Africa; and Neoceratosauria (Upper Ju-
rassic) which includes Ceratosaurus (Gilmore, 1920)
from North America and Elaphrosaurus (Janensch,
1920, 1929) from Africa. In the Cretaceous the last
Neoceratosauria is represented by abelisaurids living
in Gondwanan sub-continents (South America, Ma-
dagascar and India).
Originally, Ceratosauria included Coelophysidae
(Dilophosaurus, Coelophysis and Syntarsus) and Cerato-
saurus (Rowe and Gauthier, 1990). Later, several au-
thors recognized valid synapomorphies between
Abelisauridae and Ceratosaurus, and the clade Neo-
ceratosauria (Novas, 1992) was erected to include
Ceratosaurus, Abelisauridae and Noasaurus. Subse-
quently Elaphrosaurus and Ligabueino have been in-
cluded in a clade named Abelisauroidea (Bonaparte,
1991a, 1996; Holtz, 1994). However, the inclusion of
Elaphrosaurus has been questioned (Holtz, 1994;
Padian et al., 1999), as well as the monophyly of this
group (Rowe et al., 1997; Padian et al., 1999). Finally,
some differences between Noasaurus and Abelisau-
ridae (Bonaparte and Powell, 1980; Bonaparte and
Novas, 1985) were recognized, and the name Abeli-
sauria was erected by Novas (1992).
The family Abelisauridae (Bonaparte and Novas,
1985; Novas, 1997; Sampson et al., 1998) is character-
ized by: middle and anterior cervicals with anterior
process on each epipophysis; anteroposteriorly short
and deep premaxilla; dorsoventrally deep snout at
the level of the narial openings; frontals dorsoven-
trally thickened; posterior surface of the basioccipital
wide and smooth below the occipital condyle; loose
contacts among dentary, splenial and all theropod
postdentary bones; premaxilla with reduced to ab-
sent palatal process; rostral process of the lacrimal
strongly reduced or absent; lacrimal with pronunced
suborbital process; broad lacrimal-postorbital con-
AMEGHINIANA 41 (4), 2004
Figure 8. Ekrixinatosaurus novasi, co-ossified astragalus and calca-
neum; note the short ascending process on the astragalus / astrá-
galo coosificado y calcáneo; nótese el proceso ascendente corto en el as-
A new theropod dinosaur from Patagonia 561
tact; long axis of postorbital oriented rostroventral-
caudodorsal; postorbital with a pronounced subor-
bital process. We add: neural spine in posterior cer-
vicals lower than epipophyses, and large transverse
processes with fore and aft extensions on the distal
end of the middle and posterior caudals, recognized
by Coria et al. (2002) as an autopomorphy of
Aucasaurus garridoi.
Fossil record and distribution of abelisaurids
The fossil record of abelisaurids includes
Ligabueino andesi (Bonaparte, 1996) from the Lower
Cretaceous of South America, Xenotarsosaurus bona-
partei (Martínez et al., 1986), Ilokelesia aguadagranden-
sis (Coria and Salgado, 1998) and Ekrixinatosaurus no-
vasi from the “Middle” Cretaceous of South America;
Noasaurus leali (Bonaparte and Powell, 1980),
Abelisaurus comahuensis (Bonaparte and Novas, 1985),
Carnotaurus sastrei (Bonaparte, 1985; Bonaparte et al.,
1990), Velocisaurus unicus (Bonaparte, 1991b),
Aucasaurus garridoi (Coria et al., 2002), Indosuchus rap-
torius (Huene and Matley, 1933), Indosaurus matleyi
(Huene and Matley, 1933), Majungatholus atopus and
Masiakasaurus knopfleri (Sampson et al., 1998; 2001)
from the Upper Cretaceous of South America, India
and Madagascar.
The fossil record of abelisaurids in continental
Africa (Russell, 1996) has been controversial (Samp-
son et al., 1998). Sampson et al. (1998) proposed that
the origins of Abelisauridae occurred after the isola-
tion of Africa; therefore, the present distribution of
this clade is the result of dispersion between the
AMEGHINIANA 41 (4), 2004
Figure 9. A, one of the two most parsimonious trees obtained in this study showing the phylogenetic relationships of Ekrixinatosaurus
novasi gen. et sp. nov. The tree is based on 13 characters. TL = 14; CI = 0.9286; RI = 0.9375; RC = 0.8705. B, Strict consensus tree / A, uno
de los dos árboles más parsimoniosos que se obtuvieron en este estudio mostrando las relaciones filogenéticas de Ekrixinatosaurus novasi gen. et sp.
nov. El árbol está basado en 13 caracteres. TL = 14; CI = 0.9286; RI = 0.9375; RC = 0.8705. B, Árbol de consenso estricto.
J.O. Calvo, D. Rubilar-Rogers and K. Moreno
Indo-Madagascan province and South America
through continental links that persisted until the Late
Cretaceous. According to this hypothesis, abeli-
saurids never existed in continental Africa. On the
other hand, Lamanna et al. (2002) report an Abeli-
sauridae maxilla from the early Late Cretaceous
(middle Cenomanian-Turonian) deposits, extended
the origin of this family to pre-Senonian (Coniacian-
Maastrichtian) times. These authors suggest that the
known occurrence of Abelisauridae may reflect a for-
mer pan-Gondwanan distribution. The discovery of
Ekrixinatosaurus in the Candeleros Formation (Al-
bian-Cenomanian) is consistent with this hypothesis.
Nevertheless, an additional scenario is that Abeli-
sauridae entered continental Africa via a landbridge,
between NE Brazil and Nigeria-Cameroon, before
the major continental fragmentation of the Cenoma-
nian-Turonian. This hypothesis is based on the
strong faunal similarity of the Albian-Cenomanian
fossil assemblage found in Patagonia represented by
carcharodontosaurid theropods (Coria and Salgado,
1995; Sereno et al., 1996), Diplodocimorpha,
Titanosauria, and Titanosauridae sauropods; and
those recorded in northwestern continental Africa
(Calvo, 1999).
We thank to Leonardo Salgado and Susana Heredia (Museo de
Paleontología, Universidad Nacional del Comahue) for their help
and useful comments. We also thank to J. Hutchinson (University
of California, Berkeley), P. Currie (Tyrrell Museum of
Palaeontology), K. Carpenter (Denver Museum of Natural
History) and G. Paul for reviewing and improving the manuscript
and the English version. J. Bonaparte and F. Novas (Museo
Argentino de Ciencias Naturales “Bernardino Rivadavia”) for let-
ting us see the holotype of Carnotaurus and for providing us infor-
mation about abelisaurids; and R. Coria (Museo Municipal de
Plaza Huincul) for access to specimens under his care. The
Sociedad Paleontológica de Chile (SPACH) also helped in differ-
ent aspects of this study. This work was supported by Gaseoducto
del Pacífico Company, the National University of Comahue and
ANCyT-BID 802/OC-AR-PICT N07-01513/99 to JOC.
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Recibido: 25 de marzo de 2004.
Aceptado: 10 de noviembre de 2004.
List of 13 character and character status of Neotheropoda used for
cladistic analysis (table 1). character codes: 0, primitive; 1, derived;
? missing or uncertain. Some sources for the character analysis are:
Coria et al. 2002; Coria and Salgado, 1998; Gauthier, 1986; Novas,
1991; 1992; Sampson et al., 1998; Carrano et al., 2002.
1) Maxilla-jugal contact posteroventral directed: 0, absent; 1, pre-
2) Subvertical ascendent ramus of the maxilla: 0, absent; 1, pre-
3) Ventral convex border of dentary: 0, absent; 1, present.
4) Skull, external sculpturing: 0, absent; 1, present.
5) Frontals and parietals: 0, unfused, 1, fused.
6) maxilla-jugal contact: 0, short; 1, long, broad.
7) ventral process of postorbital: 0, ventrally; 1, o cranioventrally
8) Intraorbital projection of ventral process of postorbital: 0, ab-
sent; 1, present.
9) Cranial process of cervical epipophyses: 0, absent; 1, present.
10) Hypertrophied epipophysis: 0, absent; 1, present.
11) High of neural spine in cervicals: 0, considerably higher than
epipophysis; 1, lower or equal than epipophysis.
12) Dorsal surface of cervical neural arches clearly delimited
from lateral surface of diapophyses: 0, absent; 1, present.
13) Transverse processes of caudal vertebrae: 0, unexpanded or 1,
expanded anteroposteriorly at ends
Table 1. Data matrix for the distribution of the 13 characters listed
above among the 8 taxa considered / Matriz de platos para la dis-
tribución de 13 caracteres para los 8 taxones considerados.
Taxon 5 10
TETANURAE 0 0 0 0 0 0 0 0 0 0 0 0 0
Ceratosaurus 1 0 100 000 00000
Ilokelesia ? ? ??? ?01 01111
Carnotaurus 1 1 111 111 11111
Ekrixinatosaurus 1 1 111 ?11 01111
Majungatholus 1 1 111 111 0111 ?
Masiakasaurus ? ? 00? ??? 01100
Aucasaurus 1 11111??11111
AMEGHINIANA 41 (4), 2004
... Furthermore, the size of the alveoli in OPH2028a is more than twice those of all known abelisaurid maxillae from the KKCA (Ibrahim et al. 2020). Although a large femur from the Cenomanian of Morocco may indicate a large-bodied abelisaurid in the KKCA (Chiarenza and Cau 2016), the size of the latter individual is inferred to be comparable to Ekrixinatosaurus: given that the maxillary alveoli of the latter taxon are not longer than 65% of those of OPH2028a (see Calvo et al. 2004), we consider it unlikely that OPH2028a might belong to a yet unknown giant abelisaurid. We thus consider more parsimonious that the maxilla here described belongs to a carcharodontosaurid. ...
The ‘Kem Kem Compound Assemblage’ (KKCA) along the Algerian-Moroccan border is a series of fossiliferous localities, Cenomanian in age, particularly rich in large-bodied theropod dinosaurs. Two species of carcharodontosaurid allosauroids have been identified in these units, Carcharodontosaurus saharicus and Sauroniops pachytholus. Recently, the validity of the second species has been challenged, and all carcharodontosaurid material from the KKCA has been referred uniquely to the former species. Here, we describe a new theropod cranial material from the KKCA which is referred to Carcharodontosauridae, including one partial maxilla which shows a morphology distinct from that of C. saharicus. We review the arguments used to interpret Sauroniops holotype as an immature individual of Carcharodontosaurus and show that they were based on non-homologous comparisons and on the misinterpretation of the original description of S. pachytholus: The latter is confirmed to be a valid taxon, distinct from C. saharicus and with an inferred body size comparable to the largest carcharodontosaurids. The presence of more than one giant carcharodontosaurid species in the Cenomanian of Morocco recalls the carcharodontosaurid diversity from penecontemporary units from Argentina.
... The centrum lacks a ventral keel, as is also the case in Majungasaurus [27] and Viavenator exxoni [28,30]. In ventral view, a marked constriction is observed in the middle part of the centrum, as in caudal cervical vertebrae of many taxa within Abelisauria (= Noasauridae + Abelisauridae) [3,40,41] such as Carnotaurus, Majungasaurus, Viavenator, the generically indeterminate Patagonian mid-Cretaceous abelisaurid MPM-99 [31] and (less markedly) Ekrixinatosaurus novasi [42], Elaphrosaurus [34,35] and Masiakasaurus [37]. ...
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Numerous non-avian theropod dinosaur fossils have been reported from the Upper Cretaceous (Cenomanian) Bahariya Formation, Bahariya Oasis, Western Desert of Egypt, but unambiguous materials of Abelisauridae have yet to be documented. Here we report Mansoura University Vertebrate Paleontology Center (MUVP) specimen 477, an isolated, well-preserved tenth cervical vertebra of a medium-sized abelisaurid from the Bahariya Formation. The new vertebra shows affinities with those of other Upper Cretaceous abelisaurids from Madagascar and South America, such as Majungasaurus crenatissimus , Carnotaurus sastrei , Viavenator exxoni and a generically indeterminate Patagonian specimen (Museo Padre Molina specimen 99). Phylogenetic analysis recovers the Bahariya form within Abelisauridae, either in a polytomy of all included abelisaurids (strict consensus tree) or as an early branching member of the otherwise South American clade Brachyrostra (50% majority rule consensus tree). MUVP 477, therefore, represents the first confirmed abelisaurid fossil from the Bahariya Formation and the oldest definitive record of the clade from Egypt and northeastern Africa more generally. The new vertebra demonstrates the wide geographical distribution of Abelisauridae across North Africa during the middle Cretaceous and augments the already extraordinarily diverse large-bodied theropod assemblage of the Bahariya Formation, a record that also includes representatives of Spinosauridae, Carcharodontosauridae and Bahariasauridae.
... The ventral surface of the transverse process of C7 is convex, except in its distal portion (insertion area of M. ilio-ischiocaudalis), which precedes the bone ridge of the fan-shaped distal projection, where is almost plane (Fig. 11). The anterior and posterior centrodiapophyseal laminae are low, forming rounded ridges that are most evident in the proximal third of the transverse process, where the laminae delimit the three fossae on the lateral surface (Fig. 6B), as observed in Pycnonemosaurus (Delcourt, 2017), but differing from the robust laminae of Ekrixinatosaurus (Calvo et al., 2004). The infradiapophyseal fossa (=medial centrodiapophyseal fossa) is triangular shaped and relatively shallow, with its deepest point at its posterodorsal surface. ...
The Late Cretaceous Marília Formation (Bauru Group, Bauru Basin) is a geological unit that occurs on São Paulo, Minas Gerais, Goiás, and Mato Grosso do Sul states, Brazil. This formation consists predominantly of paleosols developed in a semiarid/arid environment and recent reappraisal of its formerly known members reduced its lithological composition and geographical distribution. Hence, the Marília Formation has a very sparse vertebrate fossil record without named species so far. In this contribution we describe a new abelisaurid theropod (Dinosauria) from this unit, namely Kurupi itaata gen. et sp. nov., discovery in the Municipality of Monte Alto, western São Paulo State. The holotype MPMA 27-0001/02 consists of three caudal vertebrae and the partial pelvic girdle. Kurupi itaata gen. et sp. nov. shares with other South American abelisaurids fused ischia and caudal vertebrae with long and laterodorsally oriented transverse processes, with fan-shaped distal ends. Autapomorphies of the new theropod include the variation of ∼15º of the inclination of the transverse process between the first (C1) and seventh (C7) caudal vertebra; C1 with anterolaterally projected triangular process placed below the proximodistal mid-portion of the transverse process, and a notch at the anterodistal portion of the transverse process, between a shelf-like process and the anterodistal corner of the transverse process; and anterior caudal vertebrae (present in C1 and C7, inferred in the others) with a cuneiform process, anterodorsally projected, located on the dorsal surface of the transverse process. Phylogenetic analysis recovered Kurupi itaata gen. et sp. nov. among abelisaurid theropods, but was nested in an unresolved massive polytomy of the entire clade. Taphonomic traits on the studied specimens corroborate previous proposals for the paleoenvironmental context of the Marília Formation. Kurupi itaata gen. et sp. nov. was about 5 meters long, with a rigid tail, and cursorial locomotion as indicated by its a muscles attachment and bones anatomy. This new taxon contributes to the knowledge of the Maastrichtian continental fauna of Brazil and increases the diversity of medium-sized abelisaurids in western Gondwana.
... The Patagonian Late Cretaceous record of abelisaurids spans from the Cenomanian (Candeleros Formation) up to the Maastrichtian (La Colonia Formation) (Bonaparte, 1985;Calvo et al., 2004), and encompasses the highest diversity of the clade (Novas et al., 2013). The most distinguishable features of Abelisauridae include: ornamented snout bones and cranial roof; broad pre-and postspinal fossae in cervical vertebrae; presence of anterior and posterior centrodiapophyseal laminae in the anterior and middle caudal vertebrae; extremely reduced ulna and radio; hemispherical humeral head; pickaxe-like lateral processes on caudal vertebrae; tibia with axe-shaped cnemial crest; and the presence of a fossa on the ventral surface of pedal ungual phalanges, instead of a flexor tubercle (e.g. ...
Abelisauridae is a theropod clade with a wide distribution in the Late Cretaceous of Gondwana. Some of the best preserved abelisaurid specimens were recovered from Patagonia (Argentina) such as Skorpiovenator, Ilokelesia, Carnotaurus and Aucasaurus. Here we describe a dorsal part of a neural spine; a middle caudal vertebra; a distal part of a left metatarsal IV; a complete right phalanx IV-1; left phalanges IV-1, 2 and 3; and a pedal ungual phalanx. These materials were recovered from the same quarry of a recently published indeterminate abelisaurid specimen (MPCN-PV-69). The most distinctive characters are a triangular shape of the distal end of metatarsal IV (present in other abelisauroids); phalanx IV-1 with the proximal surface dorsoventrally tall and the ventral surface wider than the dorsal one causing a medial tilting of bone (set of features considered autapomorphic in Velocisaurus, although is also present in different abelisaurids); phalanx IV-1 and 2 with a ridge which spans from the proximodorsal projection, splits in two branch and surrounds a laterally displaced and obliquely oriented oval hyperextensor pit; a pedal ungual phalanx with two medial and lateral vascular grooves, and lacking a flexor tubercle (abelisauroids synapomorphies). The mentioned feature of phalanges IV-1 and 2 is only found among abelisaurids and is here considered as a possible new synapomorphy of Abelisauridae. Thus, besides they constitute new abelisaurid remains from Patagonia, the new materials provide valuable morphological data that could expand the diagnosis of Abelisauridae.
Abelisaurids are medium–large-sized theropod dinosaurs that were predominant in the carnivorous fauna during the Late Cretaceous of Gondwana. These predators are abundant in the Cretaceous fossil strata of Patagonia, which yield the best record for this group. In the Late Cretaceous, abelisaurids appear in almost all regions of Gondwana and in all stages, except for the Coniacian, in which they are globally unknown. Here we describe a new abelisaurid, Elemgasem nubilus gen. et sp. nov., from the Portezuelo Formation (Turonian–Coniacian), Patagonia, Argentina. The palaeohistology of the appendicular bones of Elemgasem shows that the holotype was a subadult individual, but had achieved sexual maturity. This taxon is based on several axial and appendicular elements, and is diagnosed by the presence of a marked pattern of rugosity on the lateral surface of the fibula and a dorsoventrally deep lateral wall of the calcaneum. Moreover, the posterior caudal vertebrae have a morphology slightly different from any other abelisaurid. Elemgasem nubilus is recovered as an unstable taxon within Brachyrostra, given that it was recovered as sister taxon of Furileusauria or in several positions within this clade. Despite the problematic phylogenetic relationships of Elemgasem nubilus, it is important because it is the first abelisaurid from the Turonian–Coniacian interval and it increases the diversity of this theropod family at a time of marked turnover in the tetrapod fauna of South America, global climate change, and mass extinction events recorded worldwide in the marine realm.
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The Late Cretaceous theropod fauna of South America is composed of Abelisauridae, Noasauridae, Spinosauridae, Carcharodontosauridae, Megaraptora, and Coelurosauria. These groups include mostly small (Noasauridae and Coelurosauria) and medium- tolarge-sized taxa (Carcharodontosauridae, Abelisauridae, and Megaraptora). Some of these lineages are predominantly Gondwanic (Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptora) and poorly represented in Laurasian landmasses. Particularly, several theropods have been reported from Patagonia, known either due to distinct anatomical features or due to their high degree of preservation, such as Carnotaurus, Skorpiovenator, Giganotosaurus, Megaraptor, Alvarezsaurus, and Unenlagia. Here we describe a new incomplete tibia (MAU-PV-CM-653) from the Sierra Barrosa Formation (middle Coniacian, Upper Cretaceous), Patagonia, Argentina. MAU-PV-CM-653 shows an anteroposteriorly reduced cnemial crest that is strongly curved laterally. Finally, the tibia lacks a proximal extension of the fibular crest. These traits are reminiscent of tetanuran morphology and, together with the stratigraphic provenance of MAU-PV-CM-653, they allow us to assign it to an allosauroid theropod, thus improving the Allosauroidea global record for the middle Late Cretaceous.
Several studies have used isolated crocodyliform and theropod teeth as an important tool for taxonomic identification, as they can often be the only record of some taxa. The objective of this paper is the description and identification of the isolated crocodyliform and theropod teeth in order to clarify which taxa inhabited the western portion of the Potiguar Basin during mid-Cretaceous. The material consists of six tooth crowns from Açu Formation (Albian–Cenomanian), Potiguar Basin, northeastern Brazil. The crowns were identified by a set of qualitative (morphological comparisons and cladistics) and quantitative analyses. UFRJ-DG 659Rd was identified through morphological comparison as a peirosaurid crocodyliform due to its true ziphodont condition, enamel with an irregular texture, and faint lingual fluting. Five of the tooth crowns were identified as abelisaurid theropods based on the results of the cladistic analysis and morphological comparison, with the quantitative analysis supporting this result only for two of the five teeth. This result represents the first report of peirosaurids and abelisaurids in Potiguar Basin, and possibly one of the oldest abelisaurid records in Brazil.
Two new specimens of abelisaurid theropods from La Invernada fossil area (Bajo de la Carpa Formation; Santonian) are described. They correspond to an incomplete skull and several postcranial remains. MAU-Pv-LI-582 (skull) shares some morphological traits with other furileusaurs (Viavenator exxoni and Llukalkan aliocranianus) from the same area, as: presence of a rounded knob on the anteromedial border of the supratemporal fossa, large foramina for the caudal middle cerebral veins, and a triangular basisphenoid recess with Llukalkan, and a basituberal web ventrally concave, a large common foramen for the exit of CNs III and IV, and particularly the absence of a caudal tympanic recess with Viavenator. MAU-Pv-LI-665 (vertebrae and ribs) shares some features with Viavenator, such as the presence of a single pneumatic foramen in the mid cervical centrum, and the shape and orientation of the neural spine of the mid dorsal vertebra. These findings, added to the previous ones, not only reveal the abundance of abelisaurids in this geographical area, but also the variety of morphotypes that coexisted during the middle of the Upper Cretaceous, at least in the north of Argentine Patagonia.
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We describe the osteology of the new small theropod dinosaur Masiakasaurus knopfleri, from the Late Cretaceous Maevarano Formation of northwestern Madagascar. Approximately 40% of the skeleton is known, including parts of the jaws, axial column, forelimb, pelvic girdle, and hind limb. The jaws of Masiakasaurus are remarkably derived, bearing a heterodont, procumbent dentition that is unknown elsewhere among dinosaurs. The vertebrae are similar to those of abelisauroids in the reduction of the neural spine, lack of pleurocoelous fossae on the centrum, and extensively pneumatized neural arch. The limb skeleton is relatively gracile and bears numerous abelisauroid synapomorphies, including a rounded humeral head, peg-and-socket iliac-pubic articulation, prominent femoral medial epicondyle, expanded tibial cnemial crest, and double-grooved pedal unguals. The femora and tibiae show evidence of dimorphism. More specific features shared between Masiakasaurus, the Argentine Noasaurus, and the Indian Laevisuchus suggest that these taxa form a clade (Noasauridae) within Abelisauroidea. This is supported by a cladistic phylogenetic analysis of 158 characters and 23 theropod taxa. Additionally, Ceratosauria is rendered paraphyletic in favor of a sister-taxon relationship between Neoceratosauria and Tetanurae that is exclusive of Coelophysoidea. The unique dental and jaw specializations of Masiakasaurus suggest deviation from the typical theropod diet. Finally, the distribution of noasaurids further supports a shared biogeographic history between South America, Madagascar, and India into the Late Cretaceous.
One of the most salient advances in vertebrate paleontology in recent decades has been the settling of the question of the origin of birds, a problem that has vexed evolutionary biologists since well before Darwin. To be sure, the consensus is not unanimous, and many details of this branch of the phylogenetic tree are yet to be worked out, but we now have a much clearer picture of this problem than we had a decade ago. Less settled, but equally stimulating, has been the controversy over the origin of flight in birds and other flying vertebrates. Was there a gliding stage? Did flight begin from the ground up or from the trees down? Were birds initially arboreal? What selective pressures drove the ancestors of birds to take advantage of the aerial opportunity?