• Xenotarsosaurus bonapartei

Xenotarsosaurus is a little known theropod dinosaur genus from the group of Abelisauroidea that during the early Late Cretaceous ( Cenomanian to Turonian ) lived in what is now South America. The Fund so far only consists of a fragmentary hind leg and two vertebrae and comes from the Bajo- Barreal Formation in the Argentine province of Chubut. The only way is Xenotarsosaurus bonapartei.

The name Xenotarsosaurus (Greek xenos - " weird ", tarsus - "foot", saurus - " lizard" ) means something like "lizard with weird feet " and has the unusual structure of the ankle. The second part of the species name, bonapartei, honors the paleontologist José Fernando Bonaparte.


It was a medium-sized theropods. The femur measures 59.8 centimeters in length, which suggests a body length of about 5 meters. In the first description ( Martínez and colleagues, 1986) Xenotarsosaurus was particularly delineated on the basis of the eponymous construction of the ankle of other theropods, the distinguished themselves through the to the heel bone ( calcaneum ) fused ankle bone ( astragalus ). Today, however, this fusion is no longer considered unique feature of Xenotarsosaurus, but as a common feature of the group Ceratosauria.


The relationships of this genus are controversial because the only scant remains. In the first description of the genus, it placed Martínez Abelisauridae of what has been doubted by some later authors. So beat Coria and Rodriguez ( 1993), Xenotarsosaurus only as not classifiable representatives of Neoceratosauria ( = Ceratosauria ) to lead ( incertae sedis Neoceratosauria ). Carrano and Sampson (2008) classify this genus as a representative of Abelisauroidea, hold a position within the Abelisauridae but probable.


The only Fund ( holotype, specimen number UNPSJB - Pv -184 and -612 ) comes from the lower layer member of the Bajo- Barreal Formation north of the farm Ocho Hermanos. This specimen was recovered, together with bones of Titanosauriers Epachthosaurus. It includes two incomplete Präsakralwirbel and a partial right leg ( femur, tibia, fibula, astragalus, calcaneum ).

From the Bajo- Barreal lineup come two more fragmentary remains of Abelisauriden: an upper jaw and a Postkranialskelett. Both findings could possibly also belong to Xenotarsosaurus; since these finds but little overlap with the Xenotarsosaurus skeleton, an assignment is currently not possible.


Used literature

  • Matthew T. Carrano, Scott D. Sampson: The Phylogeny of Ceratosauria ( Dinosauria: Theropoda ). In: Journal of Systematic Palaeontology. 6, 2008, pp. 183-236, doi: 10.1017/S1477201907002246.
  • Rodolfo A. Coria: Nonavian theropods. In: Zulma Gasparini, Leonardo Salgado, Rodolfo A. Coria (ed.): Patagonian Mesozoic reptiles. Indiana University Press, Bloomington 2007, ISBN 0,253,348,579th
  • RA Coria, J. Rodríguez: Sobre Xenotarsosaurus bonapartei Martínez, Giménez, Rodríguez, y Bochatey, 1986; un problematico Neoceratosauria ( Novas, 1989) del Cretacico de Chubut. In: Ameghiniana. 30, No. 3, 1993, pp. 326-327.
  • Matthew C. Lamanna, Rubén D. Martínez, Joshua B. Smith: A definitive Abelisaurid theropod dinosaur from the early Late Cretaceous of Patagonia. In: Journal of Vertebrate Paleontology. 22, No. 1, 2002, pp. 58-69.
  • RD Martínez, O. Gimenez, J. Rodrıguez, G. Bochatey: Xenotarsosaurus bonapartei nov. Gen. et sp. ( Carnosauria, Abelisauridae ), un nuevo de la theropods Formacion Bajo Barreal, Chubut, Argentina. In: Actas IV Congresso de Argentina y Paleontologia Bioestratigrafia. 2, 1986, pp. 23-31.
  • R. S. Tykoski, T. Rowe: Ceratosauria. In: DB Weishampel, P. Dodson, H. Osmólska (eds.): The Dinosauria. 2nd edition. University of California Press, Berkeley, 2004, ISBN 0-520-24209-2, pp. 47-70.