First abelisaurid braincase (Dinosauria, Theropoda) from the late Cretaceous (campanian) of Salta province, Argentina

AGNOLIN, FEDERICO L.; SCANFERLA, C.A.; CERRONI, M.A.; GOSWAMI, A.; REUIL, S.

Congreso; Jornadas Argentinas de Paleontología de Vertebrados XXXIII; 2019

The fossil record of abelisaurid theropods in South America is mostly limited to Braziland Argentina. In Argentina, abelisaurids are generally known from Patagonia, wherethe record is relatively abundant and include well-known and complete specimens. Fornorth-western Argentina, abelisaurids are represented by incomplete and isolated bonesand teeth that remain largely unpublished. The aim of this contribution is to report anearly complete posterior portion of an abelisaurid skull. The specimen (paleontologicalcollection of the Instituto de Bio y Geociencias del NOA, IBIGEO-P 103) comes fromthe Late Cretaceous Los Blanquitos Formation (Campanian), Amblayo Valley, Saltaprovince, Argentina. It has several abelisaurid synapomorphies including heavilyornamented skull roof bones, transversely expanded nuchal crest, parietal eminenceoverlapping the supraoccipital, and dorsoventrally expanded and flattened occipitalsurface of the skull. It shows plesiomorphic abelisaurid features including absence ofskull projections like horns or bulges, poorly ossified interorbital septum, low andnarrow parietal eminence that lies at the same level than the sagittal crest, and maxillamandibularforamen for the trigeminal nerve anterior to the nuchal crest. Theplesiomorphic morphology of IBIGEO-P 103 indicates that it may represent anabelisaurid basal to those of Patagonia. The specimen possesses some autapomorphiesthat support its status as a new taxon. The finding of IBIGEO-P 103 constitutes the firstunequivocal occurrence of an abelisaurid in north-western Argentina and brings newevidence concerning the abelisaurid distribution during Late Cretaceous times in SouthAmerica.