CONICET | Buscador de Institutos y Recursos Humanos

Hadrosaurs are a common component during the Alamitian (upper Campanian-lower Maastrichtian) in northern Patagonia, although only one species has been named, "Kritosaurus" australis. Additionally, three unnominated forms are recorded in this region. Particularly, one of these was referred as to the Lambeosaurinae, although recently its taxonomic status has been discussed by some of the authors. Here, we report the discovery of abundant hadrosaur material from the Iower Member of the Allen Formation (Alamitian Land Vertebrate Age, upper Campanian-Lower Maastrichtian), cropping out in Salitral Moreno, northern Rio Negro province. The specimens were collected through successive fieldtrips conducted by the Universidad Nacional del Comahue and the Museo Carlos Ameghino, during the last 15 years. Collected bones include multiple, but not articulated individuals belonging to different ontogenetic stages. Cranial and postcranial materials are present, including: several maxillae and dentaries, premaxilla, abundant cervical, dorsal and caudal vertebrae, scapulae, coracoid, several humeri, metacarpals, ilia, ischium, femora, tibia, fibula, metatarsals and phalanges. Preliminary observation show high-spined caudal vertebrae and appendicular material resembling the "Lambeosaurine" specimen, found in the same locality. However, the presence of some dorsal vertebrae with low neural spines could imply the existence of a second taxon. Jaw bones show some plesiomorphic characters for Hadrosauridae, for instance, presence of a short diastema in the dentaries and a subvertical coronoid process. It confirm the presence of basal hadrosaurs in Allen Formation, that implies a reestudy of classical "Lambeosaurine" specimen for corroborate their phylogenetic status.

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