R. Hirayama (Teikyo Heisei University, JP) reports the discovery of an exceptionally well-preserved skeleton of the oldest known chelonioid (sea turtle). Reptiles constitute a primarily terrestrial assemblage, but several groups returned to the marine environment after the first appearance of reptiles in the Paleozoic era. Successful diversification of the chelonioid sea turtles, particularly during the Cretaceous period, was perhaps one of the most important events in the history of turtles (and marine reptiles). The fossil record of chelonioids before the Late Cretaceous has been poorly documented. The skeleton reported by the author is from the Early Cretaceous stage (about 110 mill- ion years before the present) of eastern Brazil. This specimen represents a new taxon, extending the history of chelonioids by 10 million years, and the author suggests it sheds new light on the early evolution of the group: the details of the discovery support the idea that the establishment of the salt-excreting system, and the occupation of a marine habitat, may have preceded the formation of rigid paddles in the history of chelonioids.

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