Eoabelisaurus

Eoabelisaurus
Holotype in the Museo Paleontológico Egidio Feruglio in Trelew
Temporal occurrence
Middle Jurassic ( Aalenium to Bajocium )
174.1 to 168.3 million years
Locations
Chubut , Argentina ( Cañadón Asfalto Formation )
Systematics
Lizard dinosaur (Saurischia) Theropoda Ceratosauria Abelisauridae Eoabelisaurus
Scientific name
Eoabelisaurus
Pol & Rauhut , 2012
Art
Eoabelisaurus mefi

Eoabelisaurus is a genus of theropod dinosaurs from the group of Abelisauridae . So far, a single, almost complete skeleton is known that discovered in Patagonia and by paleontologists in 2012, Diego Pol and Oliver Rauhut described was. Eoabelisaurus comes from the Middle Jurassic and is thus the oldest member of the Abelisauridae discovered to date; the next oldest records of this group are more than 40 million years younger. The find thus enables first insights into the early evolution of the Abelisaurids - for example, it shows that the extreme shortening of the forelegs, which can be found in all representatives of this group, began with the reduction of the elements remote from the body. Furthermore, this find leads to a re-evaluation of paleobiogeographical hypotheses. While it was previously assumed that the Abelisaurids emerged as a group restricted to the southern land masses only after the latter separated from the northern land masses, the new find shows that the Abelisaurids already existed at a time when all land masses were stillunitedto form the greater continent of Pangea were. The absence of Abelisaurids in the northern continents, according to Pol and Rauhut, could possibly indicate a desert that acted as a geographical barrier separating both landmasses before they broke up.

features

As with all Abelisaurids, it was a two-legged carnivore with a deep skull and greatly shortened forelimbs. The skeleton found is estimated to be 6 to 6.5 meters in length. As with other Abelisaurids, the skull is characterized by a rounded eye socket and a large infratemporal window (a skull window in the temporal region). While many later Abelisaurids showed a thickened skullcap with a strong texturing through numerous pits and appendages, the skullcap of Eoabelisaurus was neither thickened nor textured. The forelimbs and especially the four-rayed hands were greatly shortened. A unique feature is found in the ulna, the end of which near the body ( olecranon ) is greatly elongated and makes up 30% of the total length of this bone.

Systematics

A phylogenetic analysis by Pol and Rauhut (2012) comes to the conclusion that Eoabelisaurus is the most original known representative of the Abelisauridae and is therefore at the base of the family tree of this group.

Abelisauridae cladogram , simplified from Pol and Rauhut, 2012:
Abelisauridae   Eoabelisaurus     Rugops     Abelisaurus   Carnotaurinae   Majungasaurus     Indosaurus     Rajasaurus   Brachyrostra   Ilokelesia     Ekrixinatosaurus     Scorpiovenator   Carnotaurini   Carnotaurus     Aucasaurus
Systematic position of Eoabelisaurus .

Individual evidence

1. ↑ ^{a b c d e} Diego Pol, Oliver WM Rauhut : A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 279, No. 1741, 2012, ISSN  0080-4649 , pp. 3170-3175, doi : 10.1098 / rspb.2012.0660 .