Osteology of Ornithopod Macrogryphosaurus gondwanicus (Dinosauria, Ornithischia) from the Upper Cretaceous of Patagonia, Argentina

CALVO, JORGE O.; ROZADILLA, SEBASTIÁN; CRUZADO-CABALLERO, PENÉLOPE

CRETACEOUS RESEARCH (PRINT)

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2020 vol. 108

0195-6671

Macrogryphosaurus gondwanicus is the largest Elasmaria (Dinosauria, Ornithischia) known up to the date,from the Upper Cretaceous of Patagonia. The present contribution provides a detailed description ofMacrogryphosaurus anatomy based on the holotype and only known specimen. This dinosaur presentsseveral unique features along its vertebral column that distinguishes it from other ornithopods: the neckis notably elongated by the acquisition of an additional cervical vertebra, having 10 cervical plus 14 dorsalvertebrae, being the number of dorsals minor than in other taxa, which usually have 16. This implies thatMacrogryphosaurus represents a new ornithopod morphotype, with long neck and short thorax. Moreover, three autapomorphies are here added to the original diagnosis of Macrogryphosaurus: presence ofpoorly developed diapophyses in the cervical vertebrae, anterior and posterior processes on the boatshaped haemal arches, and a pubic foot in the postpubic process. The dorsoventral length of haemalarches indicate the ventral limit of the M. caudofemoralis longus and their posterior tapering so as thedorsal limit of the M. ilio-ischiocaudalis and its posterior ascension and dominance in the posterior-mostportion of tail, resembling to the tail of some coelurosaur dinosaurs.