INVESTIGADORES
EZCURRA Martin Daniel
artículos
Título:
An abelisauroid dinosaur with a non-atrophied manus from the Late Cretaceous Pari Aike Formation of southern Patagonia
Autor/es:
EZCURRA, M.D.; AGNOLIN, F.L.; NOVAS, F.E.
Revista:
ZOOTAXA
Editorial:
MAGNOLIA PRESS
Referencias:
Lugar: Auckland; Año: 2010 vol. 2450
ISSN:
1175-5326
Resumen:
We describe the new basal abelisauroid dinosaur Austrocheirus isasii gen. et sp. nov. from the Late Cretaceous Pari Aike
Formation of southwestern Patagonia, Argentina. The preserved remains include manual bones, a distal tibia, and some
pedal and axial elements. Austrocheirus is differentiated from other basal theropods by the presence of metacarpal III
with a dorsoventrally compressed shaft and posteriorly displaced collateral tendon fossae located at the same level of the
proximal end of distal condyles, and pedal phalanges with a conspicuous longitudinal crest delimitating the dorsal
margin of the distal collateral tendon fossae. A cladistic analysis recovered the new species as more derived than
Ceratosaurus and Berberosaurus, but within a polytomy at the base of Abelisauroidea, an assignment supported by two
abelisauroid synapomorphies: distal end of tibia with a planar vertical scar for the reception of the ascending process of
the astragalus that occupies most of its anterior surface and is medially bounded by the longitudinally oriented facet; and
scar for the reception of the ascending process with a median vertical ridge, which imbeds into a crescentic vertical
groove on the posterior surface of the ascending process of the astragalus forming an interlocking tibiotarsal articulation.
Furthermore, Austrocheirus represents the first known medium-sized Late Cretaceous abelisauroid bearing nonatrophied
hands. The evidence provided here suggests that the strong reduction of the forelimb recorded in derived
abelisaurids is not directly correlated with their increased body-size, but it seems to be an evolutionary event exclusive to
this lineage within Ceratosauria.