A new megaraptorid specimen (Theropoda, Coelurosauria) from Cañadón Amarillo (Anacleto Formation, Campanian, Upper Cretaceous), Mendoza Province, Argentina

ARIEL H. MÉNDEZ; FEDERICO A. GIANECHINI; JUAN I. CANALE; IGNACIO DÍAZ-MARTÍNEZ

Córdoba

Congreso; 33º Jornadas Argentinas de Paleontología de Vertebrados; 2019

Megaraptorids constitute a recently recognized new clade of theropod dinosaurs that have been documented in Africa, Oceania, and Asia, although the most abundant record comes from South America and especially from Argentina. Here wereport a new megaraptoran specimen (MCNA-PV 3109 to 3117 and 5119 to 5123) recovered from Cañadón Amarillo in outcrops of the Anacleto Formation, which consist of a left ulna, five manual phalanges, right and left metatarsals (Mt) II and III, and probably right pedal phalanges I-2, IV-1 and IV-5. The ulna exhibits a remarkable proximolateral tuberosity, a slightly curved shaft and a conspicuous depression on the lateroposterior end. This ulna is more robust and the olecranon process is less posteriorly projected than that of Australovenator and Megaraptor. The manual phalanx II-3 is very similar to that of Megaraptor. Metatarsals are 25% longer than those of Australovenator. Mt-II has an almost straight shaft with a slightly curved distal end. Mt-III exhibits a marked extensor fossa, which is deeper than in the Mt-III of Australovenator. The pedalphalanx IV-1 shows conspicuous proximal, ventral, medial and lateral processes; and a deep medial collateral ligament pit. The pedal ungual has lateral and medial vascular grooves nearly symmetrical. The other megaraptorid from the same area and stratigraphic levels is Aerosteon. Unfortunately, none of the bones here described overlap with those of Aerosteon, so it?s not possible to assign them to this taxon. The new specimen helps to increase the knowledge of the limb anatomy of this poorly known clade of theropod dinosaurs.