FOSSIL VERTEBRATES FROM THE LATE CRETACEOUS (CAMPANIAN) CERRO FORTALEZA FORMATION, SANTA CRUZ PROVINCE, ARGENTINA

AGNOLÍN F.; ÁLVAREZ HERRERA, GERARDO; ALEXIS M. ARANCIAGA ROLANDO

Buenos Aires

Congreso; Comgreso de la Asociacion Paleontologica Argentina; 2021

Asociacion Paleontologica Argentina

The Cerro Fortaleza Formation is a stratigraphical unit that outcrops near the Cerro Fortaleza, at northwestern Santa Cruz province. Up to the date this unit yielded fossil remains of dinosaurs, including the sauropod Puertasaurus reuili, the ornithopod Talenkauen santacrucensis, and the theropods Orkoraptor burkei and Austrocheirus isasii. Several field trips to the area resulted in the discovery of lamniform sharks, lepisosteiform fishes, the dipnoan Atlantoceratodus iheringi, chelid and meiolaniid chelonians, peirosaurid crocodyliforms, mosasaurid lepidosauromorphs, and abundant dinosaur remains (all housed at the paleontological collections of the Museo Padre Molina, Santa Cruz province, Argentina). The later include a partially articulated tail of a small-sized titanosauriform with procoelous and amphiplatyan vertebrae, and another, probably more derived form with procoelous caudals. Isolated sauropod teeth indicate the presence of a derived lithostrotian and the enigmatic Clasmodosaurus spatula. Among theropods, diverse abelisaurid and megaraptorid remains were found. A partial ulna, manual claw and metatarsal IV belonging to the holotype of Austrocheirus isasii were also found. The morphology of the new elements does not comfortably fit with abelisaurid or megaraptoran theropods. The fossil vertebrate content ofthe Cerro Fortaleza Formation indicates close biological ties with faunistic remains previously reported from the Mata Amarilla Formation (Cenomanian), but shows several differences with the overlying Chorrillo Formation (Maastrichtian). This may indicate that a strong faunistic change among vertebrates probably occurred at the Campanian/Maastrichtian boundary in the Patagonian Austral Basin.