AN UNUSUAL CIRCUMPOLAR TURTLE (TESTUDINATA: TESTUDINES) FROM THE EARLIEST LATE CRETACEOUS OF PATAGONIA, ARGENTINA.

Although the fossil record of turtles in the Cretaceous of Patagonia is diverse and abundant, the record from the Austral-Magallanes Basin (Santa Cruz Province, Argentina, and Magallanes Region, Chile) is scarce and fragmentary. This contribution presents a new record of a turtle from the Piedra Clavada Formation (early Cenomanian) found near Tres Lagos Village, Santa Cruz Province, Argentina. This new fossil is characterized by a unique combination of character states: medium-sized carapace (length circa 50 cm), shell with a smooth surface, having narrow vertebral scutes, regular neural bones longer than wide, the tips of thoracic ribs seen in dorsal view, posterior marginals reaching costal bones, and not having costo-peripheral fontanelles. Furthermore, based on paleolatitudinal reconstructions, the new turtle from the Piedra Clavada Formation lived in the circumpolar region (54º S), representing the oldest southernmost record of turtles in the Late Cretaceous of South America. Considering this unique combination of characters and the comparison with other Early--early Late Cretaceous turtles from Gondwana, we can suggest that MSV103 does not only belong to a new species but a new, previously unrecognized lineage of turtles in southern Patagonia [ABSTRACT FROM AUTHOR]