INVESTIGADORES
EZCURRA Martin Daniel
congresos y reuniones científicas
Título:
New dinosaur remains (Saurischia, Herrerasauridae) from the Ischigualasto Formation (Carnian) of NW Argentina
Autor/es:
EZCURRA, M. D.; NOVAS, F. E.
Lugar:
Trelew
Reunión:
Jornada; XXIII JORNADAS ARGENTINAS DE PALEONTOLOGÍA DE VERTEBRADOS; 2007
Resumen:
In the early 1960's, explorations conducted by Osvaldo Reig in outcrops of the Upper Triassic Ischigualasto Formation,Hoyada de Ischigualasto, San Juan Province, resulted in the discovery of an outstanding sample of dinosaur remains.Among thern, there is a partial left forelimb of a small saurischian never described before. The material (MACN-Pv18.649) includes well-preserved and articulated distal ulna, carpus, and manus, some vertebrae, and pedal phalanges.Albeit these elements match well in size, the association between the forelimb and the remaining bones is uncertain. Apreliminary cladistic analysis suggests herrerasaurid affinities for the forelimb (MACN-Pv 18.649a), supported by largelateralmost distal carpal. lateral condyle of metacarpal 1 smaller than pulley of phalanx I-1, manual digits II-III withelongated penultimate phalanx, and metacarpals IV-V palmar to the others. Nevertheless, this new hand differs fromthat of Herrerasaurus Reig in the presence of subequal ulna-ulnar articular contacts, radiale medially tapered, distal metacarpalI strongly asymmetric, and unguals with lateral grooves caudally bifurcated (autapomorphy). Furthermore,MACN-Pv 18.649a clearly distinguishes from the similar-sized Eoraptor Sereno et al., from the same formation, thus probablysuggesting a previously unrecognized taxon, enlarging the herrerasaurid, and early dinosaur, Carnian diversification.Among basal dinosaurs, MACN-Pv 18649a is one of the few in which all carpal elements are preserved in full articulation.This helps to better understand the anatomy and homology of the carpal elements of early dinosaurs, indicatingthat Herrerasaurus had five distal carpals (instead of four, as it was thought), supporting its stem-saurischian assignmentoutside Theropoda.