Name: Xenotarsosaurus ‭(‬Strange tarsus lizard‭).
Phonetic: Zee-noe-tsr-so-sore-us.
Named By: Ricardo Martínez,‭ ‬Olga Giménez,‭ ‬Jorge Rodríguez‭ & ‬Graciela Bochatey‭ ‬-‭ ‬1986.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Saurischia,‭ ‬theropoda,‭ ‬Abelisauridae‭?
Species: X.‭ ‬bonapartei‭ (‬type‭)‬.
Diet: Carnivore.
Size: Roughly estimated to be about 5.4 meters long.
Known locations: Argentina,‭ ‬Chubut Province‭ ‬-‭ ‬Bajo Barreal Formation.
Time period: Cenomanian to Turonian of the Cretaceous.
Fossil representation: Two anterior dorsal‭ (‬back‭) ‬vertebrae and a right hind limb.

       Based upon fossil remains first discovered in‭ ‬1980,‭ ‬Xenotarsosaurus was named because‭ ‬of‭ ‬the complete fusion between the astragalus and calcaneum bones of the ankle,‭ ‬something that is quite unusual for a theropod dinosaur.‭ ‬At the time of the original description,‭ ‬the rear leg of Xenotarsosaurus was shown to share some similarities with the better known Carnotaurus,‭ ‬logically leading to the identification of Xenotarsosaurus as an abelisaurid.‭ ‬However a‭ ‬1989‭ ‬study Coria et al.‭ ‬led to an alternative notion that Xenotarsosaurus may in fact be an indeterminate neoceratosaurian theropod.‭ ‬Additionally at the time of its original description,‭ ‬Xenotarsosaurus was thought to come from the Campanian of the Cretaceous,‭ ‬but a later re-assessment of the Bajo Barreal Formation now means that Xenotarsosaurus actually lived during the Cenomanian/Turonian stages of the Cretaceous.
       Xenotarsosaurus was likely one of the principal predators of the Bajo Barreal Formation,‭ ‬with possible prey species including the hadrosaurid Secerosaurus,‭ ‬and titanosaurian sauropods like Drusilasaura.

Further reading
-‭ ‬Xenotarsosaurus bonapartei nov.‭ ‬gen.‭ ‬et sp.‭ (‬Carnosauria,‭ ‬Abelisauridae‭)‬,‭ ‬un nuevo Theropoda de la Formacion Bajo Barreal,‭ ‬Chubut,‭ ‬Argentina‭ ‬-‭ ‬Ricardo Martínez,‭ ‬Olga Giménez,‭ ‬Jorge Rodríguez‭ & ‬Graciela Bochatey‭ ‬-‭ ‬1986.
-‭ ‬Sobre Xenotarsosaurus bonapartei Martínez,‭ ‬Giménez,‭ ‬Rodríguez y Bochatey,‭ ‬1986‭; ‬un problematico Neoceratosauria‭ (‬Novas,‭ ‬1989‭) ‬del Cretácico de Chubu‭ ‬-‭ ‬R.A.‭ ‬Coria‭ & ‬J.‭ ‬Rodríguez‭ ‬-‭ ‬1993.
- Allometry and body length of abelisauroid theropods: Pycnonemosaurus nevesi is the new king. - Cretaceous Research. 69: 71–89. - O. N. Grillo & R. Delcourt - 2016


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