Macrogryphosaurus

Macrogryphosaurus (meaning "big enigmatic lizard") is a genus of basal iguanodont dinosaur from the Turonian-early Coniacian age Upper Cretaceous Portezuelo Formation (Neuquén Group) of Patagonia, Argentina. It was described by Jorge Calvo and colleagues, with M. gondwanicus as type species (referring to the animal coming from Gondwana).

Macrogryphosaurus is based on MUCPv-321, a partial articulated postcranial skeleton. This specimen includes much of the vertebral column, ribs, complete pelvis, sternum, and four thoracic plates. These thin plates, situated alongside the ribcage, are like those of Talenkauen, another iguanodontian from the late Cretaceous of Argentina. Macrogryphosaurus was somewhat larger, though; MUCPv-321 is estimated at 6 meters (20 feet) long, and this individual was probably not fully grown based on the lack of fusion in some vertebrae. It therefore is one of the largest known South American ornithopods outside of hadrosaurids. A phylogenetic analysis indicates that it is related to Talenkauen as a basal iguanodontian, and Calvo and colleagues proposed a new clade, Elasmaria, for the two genera. Like other basal iguanodontians, it would have been a bipedal herbivore.