A JUVENILE MOSASAUR (TANIWHASAURUS ANTARCTICUS) FROM THE

MARTIN, J.; FERNÁNDEZ, M.;REGUERO,M.;CASSE,J.

Texas, USA

Congreso; 67th Annual Meeting, Society of Vertebrate Paleontology; 2007

Society of Vertebrate Paleontology

A juvenile mosasaurid (Squamata) was found by A.J. Kihm during a joint American- Argentine expedition to Vega Island east of the Antarctic Peninsula funded by the National Science Foundation and the Instituto Antártico Argentino. The skull of the mosasaur was found only following preparation of a concretion. Much of the anterior and dorsal portion of the cranium was preserved, as well as a quadrate and partial lower jaws. Diagnostic characters of the dentition and quadrate indicate the small skull represents that of the tylosaurine mosasaur, Taniwhasaurus antarcticus. The juvenile skull is approximately half the size of adult representatives of the species. The holotype of T. antarcticus was originally found in the late Campanian Santa Marta Formation on James Ross Island, whereas the juvenile was found in the early Maastrichtian Cape Lamb Member of the Snow Hill Island Formation, extending the stratigraphic range upward as had been expected. Remains of other tylosaurine mosasaurs had been recovered from late Maastrichtian deposits east of the Antarctic Peninsula but were not identifiable to generic level. Taniwhasaurus had originally been found in New Zealand and indicates the taxon was part of the austral Weddellian paleofaunal province. Moreover, this taxon and other juvenile marine reptile remains indicate that juvenile marine reptiles remained in the area until they were able to face open marine environments. Evidence of this behavior was recovered from the early Maastrichtian Cape Lamb Member of the Snow Hill Island Formation into the later Maastrichtian Sandwich Bluff Member of the Lopez de Bertodano Formation, a longer interval for the existence of such a refuge than heretofore known.