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Tyrannotitan, new carcharodontosaurid from Argentina



From: Ben Creisler bh480@scn.org

In case this new online paper has not been mentioned here:

Novas, F.E, S. de Valai, P. Vickers-Rich & T. Rich (2005).
A large Cretaceous theropod from Patagonia, Argentina, and 
the evolution of carcharodontosaurids. Naturwissenschaften 
online advance publication (Apr. 16, 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 
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.

Taxonomy
Theropoda Marsh, 1881 ?  Tetanurae Gauthier, 1986 
?  Allosauroidea Currie and Zhao, 1993 
?  Carcharodontosauridae Stromer 1934 
?  Tyrannotitan chubutensis gen. et sp. nov. 

Etymology
Latin words tyrannus (tyrant) and titan (giant), the 
specific name from the Chubut province, Argentina.
Holotype
MPEF-PV 1156 (Museo Paleontológico Egidio Feruglio, 
Trelew): Partial dentaries, isolated teeth, dorsals 3?8 
and 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.
Locality and horizon
La Juanita farm, 28 km NE of Paso de Indios, Chubut 
Province, Argentina (Fig. 1a). Possibly Cerro Castaño 
Member, Cerro Barcino Formation, Aptian (Musacchio and 
Chebli 1975; Codignotto et al. 1978; Rich et al. 2000).

Description highlights:
dentary 68 cm long and 14 cm deep at its rostral 
end....deep, squared off symphyseal region, with a ventral 
process or chin, as in Giganotosaurus ....
Postaxial cervical vertebrae are strongly opisthocoelous. 
Presacral vertebrae bear well developed pneumatic foramina 
and fossae......
humerus and ulna ....indicate that forelimbs were short 
and robust... Hindlimb bones are also massive, The femur 
of MPEF-PV 1157 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.