The end of a myth: The misterious ungual claw of Noasaurus leali

FEDERICO L. AGNOLÍN; SEBASTIÁN APESTEGUÍA; PABLO CHIARELLI

Oklahoma, EEUU

Congreso; Annual Meeting of the Society of Vertebrate Paleontology; 2004

Society of Vertebrate Paleontology

One of the most striking aspects of the abelisaur anatomy is the claimed presence of the raptorial second toe ungual claw reported for the noasaurid Noasaurus leali, adaptation that  resembles dromaeosaurids. The re-study of the putative ‘raptorial claw’ of Noasaurus permitted to recognize the following features: Ungual claw with a strong lateral compression and abnormally curved in lateral view. The articular medial keel is strongly developed as well as the proximo-ventral process. The lateral sulci are symmetrical. These features strongly suggest that this claw is from the manus, and that Noasaurus bore sharp and well developed prehensile manual claws. Furthermore, the absence of a dicotomized lateral sulcus and the lateral bump, rather than autapomorphic features, mostly support the manual nature of the claws. The observed symmetry in the proximal articular facets suggest its pertaining to a non-lateral digit, perhaps the second one. A second undescribed claw bear the same features and size, except for the, perhaps pathological, absence of the lateral sulcus. As a Noasaurus unique feature, both sides of the claws are sub-parallel in dorsal view. Abelisauroid claws were described from pedes material. The Noasaurus pedes are unknown, but as suggested by their closely related velocisaurines (e.g. Velocisaurus, Masiakasaurus, Santanaraptor), were probably non-raptorial, but cursorial. The presence of a deep excavation in the ventral side of the Noasaurus manual claw as well as the lack of flexor tubercle show abelisauroid affinities. The mentioned features suggest that the claimed “velocisaurid”- noasaurid lineage show a good development of the forelimbs whereas the lineage that drove to Carnotaurus shows the opposite trend.