The braincase of Albertosaurus sarcophagus: using anatomy and conformation to emphasize generic separation from Gorgosaurus libratus.

SHYCHOSKI, L.; PAULINA CARABAJAL, ARIANA; LARSSON, H; CURRIE, P.J.

Edmonton

Simposio; University of Alberta annual Symposium; 2010

Univerity of Alberta

ABSTRACT - Despite several million years of temporal separation and four previously recognized cranial characters that distinguish Albertosaurus sarcophagus from Gorgosaurus libratus, disagreement still remains concerning their taxonomic rank as disparate genera. To resolve this issue we describe the braincase of the type A. sarcophagus CMN 5600 (Horseshoe Canyon Formation, 73-68 Mya) and compare another A. sarcophagus TMP 1981.010.0001 with G. libratus UALVP 10 and G. libratus TMP 1994.012.0602 (Dinosaur Park Formation, 76-74 Mya). Major ndings that distinguish A. sarcophagus include a “W”-type nasal-frontalsuture, an anteroposteriorly compressed braincase box , a tall and anterodorsally arched nuchal crest, a 30- degree posteroventral angle of the prootic/paraoccipital process from the main axis of the braincase and a dorsoventrally tall cultriform process that is posteroventrally oriented. Furthermore, a cladistic analysis of sixty-four braincase characters supports the generic separation of A. sarcophagus and G. libratus.