INVESTIGADORES
EZCURRA Martin Daniel
artículos
Título:
The oldest rhynchosaur from Argentina: a Middle Triassic rhynchosaurid from the Chañares Formation (Ischigualasto?Villa Unión Basin, La Rioja Province)
Autor/es:
EZCURRA, M. D.; TROTTEYN, M. J.; FIORELLI, L. E.; BACZKO, M.B.; TABORDA, J. R. A.; IBERLUCEA, M.; DESOJO, J. B.
Revista:
PALAEONTOLOGISCHE ZEITSCHRIFT
Editorial:
SPRINGER HEIDELBERG
Referencias:
Lugar: HEIDELBERG; Año: 2014 vol. 88
ISSN:
0031-0220
Resumen:
Rhynchosaurs first appear in the Early Triassic
fossil record and flourished during the late Carnian as the
dominant members of several assemblages worldwide. In
Argentina, the rhynchosaur record is currently restricted to
the Ischigualasto Formation of late Carnian?earliest Norian
age. Recent fieldwork in the new locality of Brazo del
Puma, in the lowermost levels of the Chan?ares Formation,
yielded three rhynchosaur tooth-bearing bones, which were
collected five metres above the contact with the underlying
Tarjados Formation. The most complete specimen is the
posterior end of the alveolar region of a left dentary. The
dentary possesses densely packed tooth rows on the lingual
surface and medial half of the occlusal surface, showing
longitudinal Zahnreihen. The teeth of the occlusal surface
are worn flat and those of the lingual surface are organized
in multiple rows, supporting the referral of the specimen to
Rhynchosauridae. In addition, the dentary teeth are conical
to mesiodistally compressed, resembling the condition
observed in hyperodapedontines. The rhynchosaur remains
reported here are the oldest collected in Argentina and
among the oldest in South America, together with an
unnamed form from Brazil. The new rhynchosaur specimens
come from levels in which dicynodonts are numerically
dominant, whereas cynodonts are considerably less
abundant. Accordingly, the specimens reported here bolster
faunal differences within the Chan?ares Formation and add
a new faunal component to this already diverse vertebrate
assemblage.