ArticlePDF Available

A large Cretaceous theropod from Patagonia, Argentina, and the evolution of carcharodontosaurids

Authors:

Abstract and Figures

The Cretaceous Carcharodontosauridae is the latest clade of carnosaurs, including the largest predatory dinosaurs yet recorded. Albeit spectacular for their size, the skeletal anatomy of these theropods remains poorly-known, and their diversity was until recently restricted to two Cenomanian species: the highly derived Giganotosaurus carolinii, from southern South America, and the incompletely known Carcharodontosaurus saharicus, from northern Africa. Here we describe an older and basal member of the group, Tyrannotitan chubutensis gen. et sp. nov., from Aptian strata of Patagonia, Argentina. The new taxon gives new insights into the systematics and evolution of carcharodontosaurids and offers a better understanding of the evolution of Southern theropod faunas. We suggest that carcharodontosaurids radiated in Gondwana sharing with spinosaurids the role of top-predators until their extinction in Cenomanian-Turonian times. During this interval, the diplodocoid sauropods and giant titanosaurians went extinct (probably as part of a global-scale crisis), and the smaller abelisaurid theropods took dominance, reigning until the end of the Cretaceous. Electronic Supplementary Material is available.
Content may be subject to copyright.
Naturwissenschaften (2005) 92: 226–230
DOI 10.1007/s00114-005-0623-3
SHORT COMMUNICATION
Fernando E. Novas · Silvina de Valais ·
Pat Vickers-Rich · Tom Rich
A large Cretaceous theropod from Patagonia, Argentina,
and the evolution of carcharodontosaurids
Received: 11 March 2004 / Accepted: 23 February 2005 / Published online: 16 April 2005
C
Springer-Verlag 2005
Abstract The Cretaceous Carcharodontosauridae is the
latest clade of carnosaurs, including the largest predatory
dinosaurs yet recorded. Albeit spectacular for their
size, the skeletal anatomy of these theropods remains
poorly-known, and their diversity was until recently
restricted to two Cenomanian species: the highly derived
Giganotosaurus carolinii, from southern South America,
and the incompletely known Carcharodontosaurus sahar-
icus, from northern Africa. Here we describe an older and
basal member of the group, Tyrannotitan chubutensis gen.
et sp. nov., from Aptian strata of Patagonia, Argentina.
The new taxon gives new insights into the systematics
and evolution of carcharodontosaurids and offers a better
understanding of the evolution of Southern theropod
faunas. We suggest that carcharodontosaurids radiated
in Gondwana sharing with spinosaurids the role of top-
predators until their extinction in Cenomanian–Turonian
times. During this interval, the diplodocoid sauropods
Electronic Supplementary Information Supplementary
material is available for this article at
http://dx..1007/s00114-005-0623-3
F. E. Novas (
)
CONICET, Museo Argentino de Ciencias Naturales
“Bernardino Rivadavia”,
Av. Angel Gallardo 470,
1405 Buenos Aires, Argentina
e-mail: fernovas@yahoo.com.ar
Tel.: +5411-4981-9282
Fax: +5411-4981-9282
S. de Valais
CONICET, Museo Paleontol
´
ogico “Egidio Feruglio”,
Av. Fontana 140,
9100 Trelew, Argentina
e-mail: sdevalais@yahoo.com.ar
P. Vickers-Rich
School of Geosciences, Monash University,
Melbourne (Clayton), Victoria 3000, Australia
e-mail: prich@mail.earth.monash.edu.au
T. Rich
Museum Victoria,
GPO Box 666E, Melbourne, Victoria 3001, Australia
and giant titanosaurians went extinct (probably as part
of a global-scale crisis), and the smaller abelisaurid
theropods took dominance, reigning until the end of
the Cretaceous. Electronic Supplementary Material is
available.
Introduction
The fossil record of Aptian dinosaurs from Gondwana is
favourably increased with the discovery of a new carcharo-
dontosaurid theropod. The specimens, recovered in central
Patagonia, belong to the oldest carcharodontosaurid yet
recorded.
Description of specimens
Two partially disarticulated skeletons found 1 km apart
from each other (Rich et al. 2000).
Taxonomy
Theropoda Marsh, 1881
Tetanurae Gauthier, 1986
Allosauroidea Currie and Zhao, 1993
Carcharodontosauridae Stromer 1934
Tyrannotitan chubutensis gen. et sp. nov.
Etymology
The generic name is derived from the Latin words tyrannus
(tyrant) and titan (giant), the specific name from the Chubut
province, Argentina.
Holotype
MPEF-PV 1156 (Museo Paleontol
´
ogico “Egidio Feruglio,
Trelew): Partial dentaries, isolated teeth, dorsals 3–8 and
227
11–14, proximal caudal vertebra, isolated ribs and haemal
arches, incomplete left scapulocoracoid and right humerus
and ulna; pubes, ischia, and fragments of left ilium; almost
complete left femora, fibula and metatarsal II.
Paratype
MPEF-PV 1157: jugals, right dentary, isolated teeth, at-
las, cervical 9?, dorsals 7?, 10 and 13, partially preserved
fused centra of sacrals 1–5, isolated distal caudals, ribs,
right femur, incomplete left metatarsal II, pedal phalanges
2.I, 2.II, and 3.III. Paratype specimen is approximately 7%
larger than that of the holotype.
Locality and horizon
“La Juanita” farm, 28 km NE of Paso de Indios, Chubut
Province, Argentina (Fig. 1a). Possibly Cerro Casta
˜
no
Member, Cerro Barcino Formation, Aptian (Musacchio and
Chebli 1975; Codignotto et al. 1978; Rich et al. 2000).
Diagnosis
Teeth with bilobate denticles on rostral carina, deep mental
groove on dentary, posterior dorsal vertebrae with strongly
developed ligament scars on neural spines (Fig. 2; see S1
for character list).
Description
As preserved, the largest specimen (MPEF-PV 1157) has a
dentary 68 cm long and 14 cm deep at its rostral end. It has a
deep, squared off symphyseal region, with a ventral process
or “chin, as in Giganotosaurus (Calvo and Coria 2000)
(Fig. 2). It is ornamented by oblique grooves along the
ventral half of its lateral surface, passing through a band of
Fig. 1 (a) Map of Argentina, and (b) map of Chubut Province
(Argentine Patagonia) indicating La Juanita fossil site. (c) Skeletal
reconstruction and body shape of Tyrannotitan chubutensis, based on
specimens MPEF-PV 1156 and 1157. Relevant bones are labelled as
at (atlas in cranial view; MPEF-PV 1157), cd (anterior caudal verte-
bra, in lateral view; MPEF-PV 1156), co (left coracoid and proximal
end of scapula in lateral view; MPEF-PV 1156), d3–d8 (sequence of
dorsal vertebrae; MPEF-PV 1156), hu (right humerus in cranial view;
MPEF-PV 1156), ju (right jugal in lateral view, reversed; MPEF-PV
1157), fe (left femur in cranial view; MPEF-PV 1156), pu (pubes
in cranial view; MPEF-PV 1156), ph (pedal ungual of digit 2 in lat-
eral view; MPEF-PV 1157) ul (right ulna in lateral view; MPEF-PV
1156). Scale bar:10cm
228
Fig. 2 Tyrannotitan chubutensis (MPEF-PV 1157). (a), Right den-
tary in lateral view. (b), detail of dental serrations. c,d, Cervical ?9th
in right lateral (c) and cranial views (d). Scale bars: a,c,d 10 cm, and b,
1 mm. Abbreviations dp, diapophysis, e, epipophysis, f, foramina, lb,
lobes, pc, pneumatic cavity, pp, parapophysis, pz, prezygapophysis,
s, dentary sulcus
smooth bone surface along the dental margin, forming a pat-
tern of ornamentation resembling that of Giganotosaurus
and abelisaurids (e.g., Carnotaurus). Up to 16 alveoli are
present on the dentaries. As in other carcharodontosaurids,
the teeth bear marginal arcuate enamel wrinkles on the
labial side of the caudal carina (Sereno et al. 1996). How-
ever, tooth denticles from the cranial carina are bilobate in
side view, a character that seems unique among theropods.
Postaxial cervical vertebrae are strongly opisthocoelous.
Presacral vertebrae bear well developed pneumatic foram-
ina and fossae, in particular a pair of pleurocoels on cer-
vical and dorsal vertebrae. Caudal centra lack pleurocoels
or nutrient foramina, in contrast to the large pleurocoel re-
ported for Carcharodontosaurus (Stromer 1931), and the
pair of small nutrient foramina present on proximal and
mid-caudals of Acrocanthosaurus (Currie and Carpenter
2000; Harris 1998) and Giganotosaurus. The neural spines
of the dorsal vertebrae are craniocaudally long, dorsoven-
trally deep and transversely thick, and with strong ligament
scars protruding both cranially and caudally.
The coracoid and scapula are fused. The scapular blade
is narrow, and the acromial process rises abruptly from the
scapula at an angle approaching 90
. The slender shoulder
girdle of Tyrannotitan is sharply different from the un-
usually robust and highly derived one of Giganotosaurus
(Calvo 1999), in which the coracoid is reduced. Preserved
portions of humerus and ulna (MPEF-PV 1156; Fig. 2)
indicate that forelimbs were short and robust in this car-
charodontosaurid (as it also occurs in Acrocanthosaurus;
Currie and Carpenter 2000). Hindlimb bones are also
massive, and exhibit two remarkable carcharodontosaurid
synapomorphies: the femoral head is proximomedially
projected, and the fibula is proportionally short with
respect to femoral length (less than 70%). The femur of
MPEF-PV 1157 is almost complete; its estimated length
of 140 cm is slightly shorter than that in Giganotosaurus
(143 cm; Coria and Salgado 1995). The transverse width
of the femoral shaft of Tyrannotitan is 16.5 cm.
Discussion
Indisputable members of Carcharodontosauridae are
of Gondwanan distribution, and include the Aptian
Tyrannotitan and the more derived Giganotosaurus and
Carcharodontosaurus, both of Cenomanian age. We
concur with Currie and Carpenter (2000) and Coria and
Currie (2003) that Acrocanthosaurus, from the Aptian of
North America, may not belong to Carcharodontosauridae.
Opposing other authors (e.g., Sereno et al. 1996; Harris
1998; Holtz 2000; Rauhut 2003) Acrocanthosaurus is
here united to Allosaurus by three unambiguous synapo-
morphies; moreover, nine additional steps are needed to
relocate it within Carcharodontosauridae (Fig. 3; see S2
and S3 for cladistic analysis and data matrix).
Tyrannotitan helps to clarify the confusing aspects of the
skeletal anatomy of its close relative Carcharodontosaurus.
This Saharan taxon was recently diagnosed (Sereno et al.
1996) and reconstructed (Currie 1996) on the supposed
overlapping characters of specimens of Carcharodon-
tosaurus saharicus (Stromer 1931) and the problematic
theropod Spinosaurus B” (Stromer 1934). Pivotal in the
purported overlap is a stout cervical vertebra, characterized
by its low and very broad centrum, strong ventral keel,
and reduced neural spine (Sereno et al. 1996). However,
this vertebra (not found in association with specimens of
C. saharicus; P. Sereno, personal communication) shows
clear distinctions with cervicals of Tyrannotitan, Gigan-
otosaurus, and the holotype specimen of C. saharicus.On
the contrary, the cervical in question closely resembles
229
Fig. 3 Cladogram depicting phylogenetic relationships of Tyran-
notitan chubutensis within Theropoda. A dataset of 108 charac-
ters and 15 taxa was analyzed using NONA (ver. 1.8), resulting
in a single most parsimonious tree (L = 227; CI = 0.57; RI
= 0.65). Tree was rooted as in Currie and Carpenter 2000. Her-
rerasaurus and Ceratosauria were taken as outgroups. Tyrannotitan
is included in Carcharodontosauridae on the basis of the follow-
ing unequivocal synapomorphies: dentary with rostral end square-
shaped; teeth with wrinkles in the enamel next to the serrations;
pleurocoels present in dorsal vertebrae; absence of double ventral
keel in caudal vertebrae; femoral head proximo-medially angled.
See S1 for Character list, S2 for Cladistic analysis, and S3 for Data
matrix
that of Sigilmassasaurus (Russell 1996), a theropod of
uncertain phylogenetic relationships. Besides, the flattened
and acuminate pedal unguals of “Spinosaurus B” (Stromer
1934) purportedly referred as to Carcharodontosaurus by
Sereno et al. (1996, 1998), are sharply different from the
robust and curved ones of Tyrannotitan (Fig. 1, ph). Such
differences do not correspond with digit position. Also,
femur, tibia, dorsal and caudal vertebrae originally referred
as to Spinosaurus B” show clear distinctions from those of
Tyrannotitan and Giganotosaurus. In sum, diagnosis and
reconstruction of Carcharodontosaurus recently offered
(Sereno et al. 1996; Currie 1996) are based on the chi-
maeric association of specimens corresponding to different
theropod clades. In this context, we do not regard Sig-
ilmassasaurus brevicollis as a subjective junior synonym
of C. saharicus, as recently proposed (Sereno et al. 1998).
From Aptian through Cenomanian times Gondwana
was inhabited by large theropods including carcharo-
dontosaurids, spinosaurids, and the bizarre tetanuran
Bahariasaurus (Stromer 1934; Sereno et al. 1998).
This “mid”-Cretaceous fauna was also composed of
huge titanosaurs (e.g., Argentinosaurus, Argyrosaurus,
Paralititan), basal diplodocoids (e.g., dicraeosaurids
and rebbachisaurids), and in northern Africa, crocodiles
reached up to 12 m in length (e.g., Stomatosuchus and
Sarcosuchus) (Stromer 1936; Smith et al. 2001; Salgado
2001; Sereno et al. 2001). In the post-Turonian, carchar-
odontosaurids and spinosaurids become rare or absent in
South America, being replaced by smaller abelisauroids.
Coincidently, the following reptiles are no longer present
in the Southern landmasses after the Turonian: huge
pholidosaurid crocodiles, large basal iguanodontians,
and diplodocoids (following Chiappe et al. 2001; Currie
Rogers and Forster 2004, and Apestegu
´
ıa 2004,we
interpret Antarctosaurus wichmanianus as a titanosaurid,
thus countering Sereno et al. 1999, who envisaged this
Patagonian taxon as a rebbachisaurid). After the strong
decline of carcharodontosaurids and the virtual extinction
of spinosaurids at the end of the Cenomanian, theropod
assemblages from South America, Madagascar and India
consisted mainly of comparatively smaller abelisauroids,
and secondarily of a wide array of tetanurans (e.g.,
Megaraptor, coelurosaurians). Although abelisauroid
diversification was underway at least from the Early
Cretaceous (e.g., Carrano et al. 2002; Rauhut 2003), they
become abundant and large during Late Cretaceous times.
Notably, the “mid”-Cretaceous faunal transformations
described above for South America may parallel the
faunal replacement that occurred in North America,
where Aptian carnosaurs (e.g., Acrocanthosaurus), basal
titanosauriforms, and large basal iguanodontians, were
replaced in the Cenomanian by hadrosaurs, ceratopsians
and tyrannosaurids (Bakker 1977; Kirkland 1997; Britt and
Stadman 1997; Harris 1998). This suggests that a faunal re-
placement took place probably at a global scale at the same
general time interval. Studies of the still poorly known
“mid”-Cretaceous terrestrial communities will contribute
to better understanding of the major ecological changes
that preceded the terminal Mesozoic mass extinction event.
Acknowledgements We thank L. Guerrero, P. Puerta, R. Vacca
and their team for the discovery, excavation and preparation of the
specimens; L. Salgado, P. Currie, and P. Posadas for suggestions
on early drafts; and R. Coria and R. Carolini for access to speci-
men of Giganotosaurus carolinii. Finnancial support received from
Agencia Nacional de Promoci
´
on Cient
´
ıfica y T
´
ecnica, CONICET,
National Geographic Society, and The Jurassic Foundation (to FEN)
is gratefully acknowledged. Fieldwork was sponsored by Museo Pa-
leontol
´
ogico “Egidio Feruglio.
References
Apestegu
´
ıa S (2004) Bonitasaura salgadoi gen. et sp. Nov.: a
beaked sauropod from the Late Cretaceous of Patagonia.
Naturwissenschaften 91:493–497
Bakker RT (1977) Tetrapod mass extinctions—a model of the
regulation of speciation rates and inmigration by cycles of
topographic diversity. In: Hallam A (ed) Patterns of evolution
as illustrated by the fossil record. Elsevier Scientific Publishing,
Amsterdam, pp 439–468
Britt BB, Stadman KL (1997) Dalton Wells Quarry. In: Currie P,
Padian K (eds) Encyclopaedia of dinosaurs, Academic Press,
New York, pp 165–166
Calvo JO (1999) Dinosaurs and other vertebrates of the Lake
Ezequiel Ramos Mex
´
ıa Area, Neuqu
´
en-Patagonia, Argentina.
In: Tomida Y, Rich TH, Vickers-Rich P (eds) Proceedings of the
Second Gondwanan Dinosaur Symposium, National Science
Museum Monographs 15, Tokyo, pp 13–45
Calvo JO, Coria RA (2000) New specimen of Giganotosaurus
carolinii (Coria and Salgado, 1995), supports it as the largest
theropod ever found. GAIA 15:117–122
Carrano MT, Sampson SD and Forster CA (2002) The osteology
of Masiakasaurus knopfleri, a small abelisauroid (Dinosauria:
Theropoda) from the Late Cretaceous of Madagascar. J Vert
Paleontol 22:510–534
230
Chiappe LM, Salgado L, Coria RA (2001) Embryonic skulls of
titanosaur sauropod dinosaurs. Science 293:2444–2446
Codignotto J, Nullo F, Panza J, Proserpio C (1978) Estratigraf
´
ıa del
Grupo Chubut entre Paso de Indios y Las Plumas, Provincia del
Chubut, Argentina. Actas VII Congreso Geol
´
ogico Argentino,
pp 471–480
Coria RA, Currie PJ (2003) The braincase of Giganotosaurus
carolinii, (Dinosauria: Theropoda) from the Upper Cretaceous
of Argentina. J Vertebr Paleontol 4:802–811
Coria RA, Salgado L (1995) A new giant carnivorous dinosaur from
the Cretaceous of Patagonia. Nature 377:224–226
Currie PJ (1996) Out of Africa: meat-eating dinosaurs that challenge
Tyrannosaurus rex. Science 272:971–972
Currie PJ, Carpenter K (2000) A new specimen of Acrocanthosaurus
atokensis (Theropoda, Dinosauria) from the Lower Cretaceous
Antlers Formation (Lower Cretaceous, Aptian) of Oklahoma,
USA. Geodiversitas 22:207–246
Currie Rogers K, Forster C (2004) The skull of Rapetosaurus
krausei (Sauropoda: Titanosauria) from the Late Cretaceous of
Madagascar. Journ Vert Pal 24:121–144
Harris JD (1998) A reanalysis of Acrocanthosaurus atokensis, its
phylogenetic status and paleobiogeographic implications, based
on a new specimen from Texas. Bull New Mexico Mus Nat
Hist Sci 13:1–75
Holtz TR (2000) A new phylogeny of the carnivorous dinosaurs.
GAIA 15:5–61
Kirkland J (1997) Cedar Mountain Formation. In: Currie P, Padian
K (eds) Encyclopaedia of Dinosaurs, Academic Press, New
York, pp 98–99
Musacchio E, Chebli W (1975) Ostr
´
acodos no marinos y car
´
ofitas
del Cret
´
acico inferior de las provincias de Chubut y Neuqu
´
en,
Argentina. Ameghiniana 12:70–96
Rauhut OWM (2003) The interrelationships and evolution of
basal theropod dinosaurs. Special Papers in Palaeontology 69:
1–213
Rich TH, Vickers-Rich P, Novas F, C
´
uneoR,PuertaP,Vacca
R (2000) Theropods from the “Middle” Cretaceous Chubut
Group of the San Jorge sedimentary basin, Central Patagonia.
A preliminary note. GAIA 15:111–115
Russell DA (1996) Isolated dinosaur bones from the Middle
Cretaceous of the Tafilalt, Morocco. Bulletin du Mus
´
eum
National d’Histoire Naturelle de Paris, 18:349–363
Salgado L (2003) Los Saur
´
opodos de Patagonia: sistem
´
atica
evoluci
´
on y paleobiologia. II Jornalas internacionales sobre
paleontologia de Dinosaurios y su Entorno, Actas, Sala de Los
Inpantes, Espa
˜
na, pp 139–168
Sereno PC, Beck AL, Dutheil DB, Gado B, Larsson HC, Lyon GH,
Marcot JD, Rauhut OWM, Sadleir RW, Sidor CA, Varrichio
DJ, Wilson GP, Wilson JA (1998) A long-snouted predatory
dinosaur from Africa and the evolution of the spinosaurids.
Science 282:1298–1300
Sereno PC, Beck AL, Dutheil DB, Larsson HCE, Lyon GH, Moussa
B, Sadleir RW, Sidor CA, Varricchio DJ, Wilson GP, Wilson
JA (1999) Cretaceous sauropods from the Sahara and the
uneven rate of skeletal evolution among dinosaurs. Science
286:1342–1347
Sereno PC, Dutheil DB, Iarochene M, Larsson HC, Lyon GH,
Magwene PM, Sidor CA, Varrichio DJ, Wilson JA (1996)
Predatory dinosaurs from the Sahara and Late Cretaceous
faunal differentiation. Science 272:986–991
Sereno PC, Larsson HCE, Sidor CA, Gado B (2001) The giant
crocodyliform Sarcosuchus from the Cretaceous of Africa.
Science 294:1516–1519
Smith JB, Lamanna MC, Lacovara KJ, Dodson P, Smith JR, Poole
JC, Giegengack R, Attia Y (2001) A giant sauropod dinosaur
from an Upper Cretaceous mangrove deposit in Egypt. Science
292:1704–1706
Stromer E (1931) Wirbeltierreste der Bahar
´
ıje-Stufe (unterstes
Cenoman). 10. Ein Skelett-Rest von Carcharodontosaurus nov.
gen. Abh. bayer. Akad. Wissensch., math-naturwiss. Abt., N.F.
9:1–23
Stromer E (1934) Wirbeltierreste der Bahar
´
ıje-Stufe (unterstes
Cenoman). 13. Dinosauria. Abh. bayer. Akad. Wissensch.,
math-naturwiss. Abt., N.F. 22:1–79
Stromer E (1936) 7.Wirbeltierreste der Bahar
´
ıje-Stufe (unterstes
Cenoman). Baharije-Kesse und Stufe mit deren Fauna und
Flora Eine erganzende Zusammenfassung. Abh. bayer. Akad.
Wissensch., math-naturwiss. Abt., N.F. 33:1–102
... Entre los primeros fósiles de la colección de paleoherpetología del MPEF se encuentra un caparazón de tortuga, Chelonoidis gringorum Simpson, 1942 (MPEF-PV 1049; Fig. 2 Rich et al., 1999(holotipo MPEF-PV 1125Carballido et al., 2011b;Fig. 2.4-6) del cual incluso se preservaron impresiones de su piel (del Valle Giménez, 2007), materiales adicionales del holotipo de Chubutisaurus insignis (MPEF-PV 1129;Salgado, 1993;Carballido et al., 2011a), el terópodo Tyrannotitan chubutensis Novas et al., 2005(holotipo MPEF-PV 1156, paratipo MPEF-PV 1157Novas et al., 2005;Canale et al., 2015), las tortugas Chubutemys copelloi Gaffney et al., 2007(holotipo MPEF-PV 1236Gaffney et al., 2007;Sterli et al., 2015a), Patagoniaemys gasparinae Sterli y de la Fuente, 2011 (holotipo MPEF-PV 3283), Yaminuechelys maior (Staesche, 1929) Bona, 2007(holotipo MPEF-PV 1933. Los materiales de tortugas y cocodrilos colectados durante esta época en la Formación Salamanca formaron el núcleo de la tesis doctoral de P. Bona (Bona, 2004) y sucesivas publicaciones (Bona y de la Fuente, 2005;Bona, 2006Bona, , 2007. ...
... Entre los primeros fósiles de la colección de paleoherpetología del MPEF se encuentra un caparazón de tortuga, Chelonoidis gringorum Simpson, 1942 (MPEF-PV 1049; Fig. 2 Rich et al., 1999(holotipo MPEF-PV 1125Carballido et al., 2011b;Fig. 2.4-6) del cual incluso se preservaron impresiones de su piel (del Valle Giménez, 2007), materiales adicionales del holotipo de Chubutisaurus insignis (MPEF-PV 1129;Salgado, 1993;Carballido et al., 2011a), el terópodo Tyrannotitan chubutensis Novas et al., 2005(holotipo MPEF-PV 1156, paratipo MPEF-PV 1157Novas et al., 2005;Canale et al., 2015), las tortugas Chubutemys copelloi Gaffney et al., 2007(holotipo MPEF-PV 1236Gaffney et al., 2007;Sterli et al., 2015a), Patagoniaemys gasparinae Sterli y de la Fuente, 2011 (holotipo MPEF-PV 3283), Yaminuechelys maior (Staesche, 1929) Bona, 2007(holotipo MPEF-PV 1933. Los materiales de tortugas y cocodrilos colectados durante esta época en la Formación Salamanca formaron el núcleo de la tesis doctoral de P. Bona (Bona, 2004) y sucesivas publicaciones (Bona y de la Fuente, 2005;Bona, 2006Bona, , 2007. ...
... Además, también asignados a dinosaurios saurópodos, se han hallado restos de cáscaras de huevo del tipo megalolítidos(Argarañaz et al., 2013). Para esta unidad en la colección del MPEF se encuentra el dinosaurio terópodo carcaradontosáurido Tyrannotitan chubutensis (holotipo MPEF-PV 1156;Novas et al., 2005). ...
Full-text available
Article
The extinct herpetofauna of the Chubut Province is one of the most diverse, temporally and spatially extensive, and well-known extinct faunas in Argentina and South America. These fossils help understanding the evolution of the herpetofauna during more than 180 million years, not only in the Patagonian region, but also in a worldwide scale due to the importance of some of them. Since its establishment in 1990, the Museo Paleontológico Egidio Feruglio (MPEF) plays a key role in the discovery, protection, study, and display of the important fossils of the Province. The paleoherpetological study at MPEF went through three different stages: the Initial, the Intermediate, and the Current stages. At present, the paleoherpetological collection contains approximately 960 specimens of amphibians and reptiles-including turtles, lepidosaurs, plesiosaurs, crocodiles, pterosaurs, dinosaurs, and birds-found in sedimentary formations that span from the Early Jurassic to the late Miocene. Based on this material, at least 32 new species were named, and more than 200 studies were published in less than three decades. © 2022 Asociacion Paleontologica Argentina. All rights reserved.
... Several authors have proposed that an extinction event occurred during the Cenomanian-Turonian boundary, affecting many vertebrate groups in both hemispheres 68,70,71 . Some authors discussed the impact of such an event, considering the posibility that this extinction was a step-wise process involving several million of years 69 . ...
... Some authors discussed the impact of such an event, considering the posibility that this extinction was a step-wise process involving several million of years 69 . Nevertheless, there is a consensus that after the Cenomanian-Turonian time interval, many dinosaurian groups became extinct in tandem with the origin, diversification, and increased numerical abundance of others 2,68,[70][71][72][73] . For the Northern Hemisphere, several authors proposed an ecological replacement during the Cenomanian-Turonian boundary 16,72,73 . ...
Full-text available
Article
Megaraptora is a theropod clade known from former Gondwana landmasses and Asia. Most members of the clade are known from the Early to Late Cretaceous (Barremian–Santonian), with Maastrichtian megaraptorans known only from isolated and poorly informative remains. The aim of the present contribution is to describe a partial skeleton of a megaraptorid from Maastrichtian beds in Santa Cruz Province, Argentina. This new specimen is the most informative megaraptoran known from Maastrichtian age, and is herein described as a new taxon. Phylogenetic analysis nested the new taxon together with other South American megaraptorans in a monophyletic clade, whereas Australian and Asian members constitute successive stem groups. South American forms differ from more basal megaraptorans in several anatomical features and in being much larger and more robustly built.
... IN GONDWANA, the Cenomanian/Turonian boundary represents a crucial time-lapse for the evolutionary history of several terrestrial tetrapod lineages, representing one of the latest faunistic replacement of Mesozoic (see Apesteguía, 2002;Leanza et al., 2004). Indeed, it precedes the final establishment of typical Late Cretaceous reptile lineages, before the extinction of non-avian dinosaurs at the Cretaceous/ Paleogene boundary (Coria & Salgado, 2005;Novas et al., 2005Novas et al., , 2013Krause et al., 2020). The Cenomanian/Turonian turnover seems to be closely related to paleoclimatic, paleogeographic, and paleoecological variations linked with the opening of the South Atlantic Ocean, which occurred during the mid-Cretaceous (Aptian-Turonian; e.g., Schlanger & Jenkyns, 1976;Arthur et al., 1987;Elder, 1987;Hut et al., 1987;Jenkyns, 2010;Pol & Leardi, 2015;Petrizzo et al., 2021). ...
Full-text available
Article
In the central Neuquén Basin, the Huincul Formation comprises thick successions of Upper Cretaceous fluvial deposits widely exposed at the south and north-west of Huincul High. The vertebrate fossil record from the Huincul Formation is very abundant, especially considering the saurischian dinosaurs, including several theropod (Mapusaurus, Taurovenator, Aoniraptor, Skorpiovenator, Ilokelesia, Gualicho, Overoraptor, Tralkasaurus, and Huinculsaurus) and sauropod specimens (Choconsaurus, Argentinosaurus, Cathartesaura, Limaysaurus, and the indeterminate rebbachisaurid MMCH-Pv-49). In this contribution, we describe new rebbachisaurid sauropod findings from the El Orejano locality (Neuquén Province, Argentina), where coarse sandstones outcrop referred to the lower section of the Huincul Formation. The new material includes three axial elements that we refer to Rebbachisauridae: a partial dorsal neural arch (MAU-Pv-EO-633), an incomplete dorsal vertebra (MAU-Pv-EO-634), and an almost complete caudal vertebra (MAU-Pv-EO-666). These new findings share different features with other members of that family, although show some morphological differences with other rebbachisaurid taxa, which suggest a more diversified fauna in the central Neuquén Basin than previously known, at least during the Cenomanian/Turonian interval. This record from the new fossiliferous locality of El Orejano allows us to improve our knowledge about the morphological diversity of the Rebbachisauridae during the early Late Cretaceous. Furthermore, it represents one of the most modern records of the family, adding new information on the last stages of the evolutionary history of rebbachisaurids.
... The addition of yet another species of giant carcharodontosaurid (body mass estimated: 4,263 kg; STAR Methods) from the lower part of the Huincul Formation, possibly coeval with Taurovenator, 5 and stratigraphically intermediate between Giganotosaurus from the underlying Candeleros Formation and Mapusaurus from younger levels of the Huincul Formation, is further indication of the high diversity of this clade shortly before its extinction by Turonian-Coniacian times. 8,20 A comparable diversity of large tyrannosaurids is known from the Campanian of western North America. 21 Despite their temporal and geographical proximity, Meraxes is readily distinguished from other Giganotosaurini by a suite of characters from throughout the skull and skeleton, including unique protuberances and rugosity patterns on the Thick colored bars represent the stratigraphic resolution for each taxon, and the color of each bar indicates their geographic provenance. ...
Article
Giant carnivorous dinosaurs such as Tyrannosaurus rex and abelisaurids are characterized by highly reduced forelimbs that stand in contrast to their huge dimensions, massive skulls, and obligate bipedalism.¹,² Another group that follows this pattern, yet is still poorly known, is the Carcharodontosauridae: dominant predators that inhabited most continents during the Early Cretaceous3, 4, 5 and reached their largest sizes in Aptian-Cenomanian times.6, 7, 8, 9, 10 Despite many discoveries over the last three decades, aspects of their anatomy, especially with regard to the skull, forearm, and feet, remain poorly known. Here we report a new carcharodontosaurid, Meraxes gigas, gen. et sp. nov., based on a specimen recovered from the Upper Cretaceous Huincul Formation of northern Patagonia, Argentina. Phylogenetic analysis places Meraxes among derived Carcharodontosauridae, in a clade with other massive South American species. Meraxes preserves novel anatomical information for derived carcharodontosaurids, including an almost complete forelimb that provides evidence for convergent allometric trends in forelimb reduction among three lineages of large-bodied, megapredatory non-avian theropods, including a remarkable degree of parallelism between the latest-diverging tyrannosaurids and carcharodontosaurids. This trend, coupled with a likely lower bound on forelimb reduction, hypothesized to be about 0.4 forelimb/femur length, combined to produce this short-armed pattern in theropods. The almost complete cranium of Meraxes permits new estimates of skull length in Giganotosaurus, which is among the longest for theropods. Meraxes also provides further evidence that carchardontosaurids reached peak diversity shortly before their extinction with high rates of trait evolution in facial ornamentation possibly linked to a social signaling role.
... Consistent with this hypothesis, dinosaurian faunas from northern Gondwana (i.e., Sahara + Brazil + Northern Argentina) are different from those of southern Gondwana (i.e., Southern Argentina + Australasia) (Broin and de la Fuente, 1993;Apesteguía, 2002;Ezcurra and Agnolín, 2012;Candeiro, 2015). Northern faunas share arganodontid, lepidosirenid, and neoceratodontid-like dipnoans, mawsoniid coelacanths, dominance of podocnemidoid pleurodire turtles, and spinosaurid dinosaurs (Apesteguía, 2002;Rana and Wilson, 2003;Novas et al., 2005Novas et al., , 2009Novas et al., , 2013Agnolín, 2010;Kellner et al., 2011;Woodburne et al., 2013;Castro et al., 2018). On the other side, southern Gondwanan faunas include the common presence of basal dipnoans, chelid pleurodiran turtles, and among theropods, a great diversity and abundance of megaraptorids (Apesteguía, 2002;Smith et al., 2008;Agnolin, 2010;de la Fuente et al., 2011). ...
Full-text available
Article
The fossil record of abelisaurid theropods in South America is mostly limited to Brazil and Argentina. In Argentina, abelisaurids are generally known from Patagonia, where their record is relatively abundant and includes well-known and complete specimens. However, for Northwestern Argentina, abelisaurids are represented by incomplete and isolated bones and teeth that remain largely unpublished. The aim of this contribution is to report a nearly complete abelisaurid braincase from the Late Cretaceous Los Blanquitos Formation (Campanian), Amblayo Valley, Salta province, Argentina. The specimen shows plesiomorphic features for abelisaurids, including a thin skull roof, absence of skull projections like horns or bulges, and low and narrow parietal eminence that lie at the same level as the sagittal crest. Furthermore, the specimen possesses some autapomorphies that support its status as a new taxon and its small size allows it to be assigned as one of the smallest abelisaurids recorded up to date. The finding of this specimen constitutes the first unequivocal occurrence of an abelisaurid in Northwestern Argentina and brings new evidence concerning the geographic distribution of the clade during Late Cretaceous times in South America.
... There are four preserved cervical vertebrae in the neck of Aerosteon, all strongly opithocoelous. Opisthocoely is present in a large array of theropods such as Allosaurus, Acrocanthosaurus or Scipionyx (Madsen 1976; Eddy and Clarke 2011; Dal Sasso and Maganuco 2011), but strong opisthocoely (ball-in-socket) comparable to Aerosteon occur in a variety of basal tetanurans such as Megaraptor, Sinraptor, Dilong and Compsognathus (Ostrom 1978;Currie and Zhao 1993;Calvo et al. 2004;Xu et al. 2004;Novas et al. 2005;. In this sense, the opisthocoely of carcharodontosaurids is notably much more developed (e.g., Giganotosaurus, Tyrannotitan) where the anterior articular surface exhibits a ball-shaped and is as long as the rest of the centrum (ballin-socket condition). ...
Article
Aerosteon riocoloradensis represents one of the most complete megaraptorans yet discovered. This theropod comes from Anacleto Formation (Campanian) of Mendoza Province, Argentina. The aims of this contribution are: to present a detailed, bone by bone description of this specimen with figures of each bone; provide comparisons to other closely related theropods; revise the original assignation and diagnosis of such taxa. Three bones were re-assigned and almost all the autapomorphies of Aerosteon were modified. Features in the vertebral columns, which are shared with other megaraptorans, show that these theropods shared features with basal coelurosaurs. Anatomical Abbreviations ACDL: Anterior centrodiapophyseal lamina; CDF: Centrodiapophyseal fossa; CPAL: Centroparapophyseal lamina; CPRL: Centroprezygapophyseal lamina; CPRF: Centroprezygapophyseal fossa; CPR-CDF: Centroprezygapophyseal-centrodiapophyseal fossa; Hye: Hyposphene; Hym: Hypantrum; ILT: Intervertebral ligament tuberosity; IPOL: Infrapostzygapophysela lamina; IZL: Intrazygapophyseal lamina; PADL: Paradiapophyseal lamina; PAD-CDF: Paradiapophyseal-centrodiapophsyeal fossa; PCDL: Posterior centrodiapophyseal lamina; POEL: Postzygaepipophysela lamina; PODL: Postzygadiapophyseal lamina; POSF: Postspinal fossa; POCDF: Postzygapophsyeal-centrodiapophyseal fossa; Poz: Postzygapophysis; PRDL: Prezygadiapophyseal lamina; PRPAF: Prezygaparapophyseal fossa; PRPAL: Prezygaparapophyseal lamina; PRSF: Prespinal fossa; PRSL: Prespinal lamina; PRD-CDF: Prezygadiapophyseal-centrodiapophyseal fossa; PRD-PADF: Prezygadiapophyseal-paradiapophyseal fossa; PRD-PODF: Prezygadiapophyseal-postzygadiapophyseal fossa; PRCDF: Prezygapophyseal-centrodiapophyseal fossa; Prz: Prezygapophyses; SDF: Supradiapophsyeal fossa; SDL: Supradiapophyseal lamina; SPOF: Spinopostzygapophyseal fossa; SPOL: Spinopostzygapophyseal lamina; SPRF: Spinoprezygapophyseal fossa; SPRL: Spinoprezygapophyseal lamina; SR(number): Sacral rib; STP(number): Sacral transverse process
Article
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.
Chapter
Although the origin of Neosauropoda probably dates back to the Early–Middle Jurassic, it is not until the Late Jurassic that Macronaria become well represented in the fossil record. Unlike the great diversity of South American titanosaurs, basal macronarians are relatively scarce in the fossil record; even so, they provide valuable information for better understanding the first steps at the origin of this clade. The only non-titanosauriform macronarian sauropod from South America is Tehuelchesaurus from the Oxfordian-Tithonian of Argentina, while all other basal macronarians found up to date are titanosauriforms (either Brachiosauridae or Somphospondyli). Brachiosaurids were abundant in the Jurassic, but they apparently became extinct at the Jurassic/Cretaceous boundary all over the world except in North America. Isolated elements from the Late Jurassic of Argentina and Padillasaurus from the Early Cretaceous of Colombia were suggested as brachiosaurids, but these assignments are questionable. Until now, no clear somphospondylans have been recorded in Jurassic levels. In South America, basal, non-titanosaur somphospondylans are represented by three taxa registered in Argentina: Chubutisaurus and Ligabuesaurus from the Early Cretaceous (Aptian–Albian) and Malarguesaurus from the Late Cretaceous (Turonian–Coniacian). Here, we provide a complete revision on the fossil record of non-titanosaur macronarians from South America and the current phylogenetic status of them.
Article
The deposits corresponding to the Upper Cretaceous Neuquén and San Jorge Gulf basins from northern and central Patagonia have provided two of the most complete sequences of terrestrial vertebrate faunas of all Gondwanan landmasses. Among the carnivorous components, the carcharodontosaurid theropods appeared as common elements during the Early Cretaceous and the earliest Late Cretaceous in northern and central Patagonia. Although recorded mostly in the lower Turonian, isolated teeth suggest their presence in younger strata in northern and central Patagonia, reaching the clade in the region as late as the early Maastrichtian. Here, we verify the assignment of such isolated teeth previously identified as belonging to Carcharodontosauridae from the Upper Cretaceous strata of northern and central Patagonia. Using three different methods, namely a cladistic analysis performed on a dentition-based data matrix, and discriminant and cluster analyses conducted on a large dataset of theropod crown measurements, we assign a tooth from Candeleros Formation to carcharodontosaurid theropods and teeth from Cerro Lisandro, Bajo Barreal, Portezuelo, Plottier and Allen formations to abelisaurid theropods. These new reappraisals provide additional evidence about the extinction of Carcharodontosauridae in South America at about the late Turonian–earliest Coniacian as part of a general faunistic turnover event, with the last clear evidence of this lineage in Patagonia coming from the early–middle Turonian.
Full-text available
Article
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.
Full-text available
Article
Many recent studies of theropod relationships have been focused on the phylogeny of coelurosaurs and the question of the origin of birds, but the interrelationships and evolution of basal theropods are still poorly understood. Thus, this paper presents a phylogenetic analysis of all theropods, but focuses on the basal members of this clade. The result supports the inclusion of Eoraptor and herrerasaurids in the Theropoda, but differs from other recent studies in two main aspects: (1) The taxa usually grouped as ceratosaurs form two monophyletic clades that represent successively closer outgroups to tetanurans. The more basal of these clades, the Coelophysoidea, comprise the majority of Late Triassic and Early Jurassic theropods. The other clade of basal theropods that are usually included in the Ceratosauria comprises Ceratosaurus, Elaphrosaurus, and abelisaurids. (2) Two monophyletic groups of basal tetanurans are recognized: the Spinosauroidea and the Allosauroidea. In contrast to other recent phylogenetic hypotheses, both clades are united in a monophyletic Carnosauria. The branching pattern of the present cladogram is in general accordance with the stratigraphic occurrence of theropod taxa. Despite the differences in recent analyses, there is a significant level of consensus in theropod phylogeny. At least four different radiations of non-avian theropods can be recognized. These radiations show different patterns in Laurasia and Gondwana, and there are increasing differences between the theropod faunas of the two hemispheres from the Triassic to the Cretaceous.
Full-text available
Article
Rapetosaurus krausei (Sauropoda: Titanosauria) from the Upper Cretaceous Maevarano Formation of Madagascar is the best-preserved and most complete titanosaur yet described. The skull of Rapetosaurus is particularly significant because most titanosaurs are diagnosed solely on the basis of fragmentary postcranial material, and knowledge of the titanosaur skull has remained incomplete. Material referred to Rapetosaurus includes the type skull from an adult that preserves the basicranium, rostrum, mandible, and palate. A second, juvenile skull preserves most of the braincase and cranial vault, as well as some of the palate and lower jaw. Here we provide a detailed description of Ropetosaurus cranial anatomy and highlight comparative relationships among known titanosaur and other neosauropod skulls. The Rapetosaurus skull is similar to those of diplodocoids in its overall shape, with retracted external nares and an elongated snout. However, extensive tooth distribution and bone articulations surrounding the external narial region and orbit are more similar to those of macronarians like Camarasaurus and Brachiosaurus. The maxilla, basicranium, paroccipital process, and pterygoid are among the most diagnostic elements of the Rapetosaurus skull, along with the enlarged antorbital fenestra, anteroventrally oriented braincase, and mandible. Titanosaur crania exhibit a greater diversity than previously recognized and, in light of Rapetosaurus, it is apparent that there is not a narrowly constrained bauplan for the skull of titanosaurs. Broad generalizations about evolution based on previously known, fragmentary fossils require re-evaluation. Ultimately, Rapetosaurus will be key in resolving titanosaur higher-level and ingroup phylogeny.
Article
The 'Gres rouges infracenomaniens' of southern Morocco, possibly of Albian age, contain evidence of one of the most diversified dinosaur assemblages known from Africa, including a relatively long-necked species of Spinosaurus and abundant but isolated bones of a peculiar theropod ('Spinosaurus B' of Stromer 1934). Also preserved are the oldest records of abelisaurids and among the oldest records of titanosaurids in Africa. Bones of infantile didnosaurs are present. The assemblage resembles that of the Bahariya Formation more than that of Gadoufaoua, possibly because of a trophic dependence upon large, freshwater fishes. It was more closely linked zoogeographically to South America than to North America.