Calvo, J.O.; Porfiri, J.D. & Novas, F.E. 2007. Discovery of a new ornithopod dinosaur from the Portezuelo Formation (Upper Cretaceous), Neuquén, Patagonia, Argentina. Arquivos do Museu Nacional, Rio do Janeiro, 65(4): 471-483.

Abstract: We describe the postcranial skeleton of a new Cretaceous ornithopod, Macrogryphosaurus gondwanicus gen.nov., sp.nov. from Patagonia, Argentina. The specimen was found in the Portezuelo Formation, Neuquén Group, Upper Cretaceous. Macrogryphosaurus gondwanicus gen.nov., sp.nov. is diagnosed by having triradiate sternum with the anterior border tribranched, two laterally placed and outwardly directed, and one centrally placed, smaller, and forwardly directed. Sternal ribs flattened, twisted and distally expanded.

Last dorsal vertebra with well-developed hyposphene. A thin plate-like are located in front of the sterna. Together with these autapomorphies, this new species of ornithopod differs from Talenkauen santacrucensis by having the pubic peduncle of ilium less developed, a more acute angle between the anterior process of ilium and the pubic peduncle, the acetabular cavity slightly marked.

Also present ten cervical vertebrae, fourteen dorsal vertebrae, epipophyses on the third cervical vertebra placed over the distal end of the postzygapophyses and posteriorly projected. The presence of plates on the lateral side of the thorax and well developed epipophyses on the third cervical vertebra, were originally interpreted as autapomorphies for the euiguanodontian Talenkauen santacrucensis. These features are also present in Macrogryphosaurus gondwanicus gen.nov, sp.nov., and are regarded as synapomorphies defining a new clade of Euiguanodontia dinosaurs comprising the two species: Elasmaria nov.

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