PROC. BIOL. SOC. WASH. 101(1), 1988, pp. 109-145 PALEOCENE TURTLES FROM THE AQUIA AND BRIGHTSEAT FORMATIONS, WITH A DISCUSSION OF THEIR BEARING ON SEA TURTLE EVOLUTION AND PHYTOGENY Robert E. Weems Abstract.— ThQ Piscataway Member of the Aquia Formation (upper Paleo-cene: Thanetian) has yielded remains of six species of turtles: Aspideretes vir-ginianus (Clark), Planetochelys savoiei (n. gen., n. sp.), Osteopygis roundsi (n. sp.), Dollochelys coatesi (n. sp.), Catapleura ruhoffi (n. sp.), and Allopleuron insularis (Cope). The Brightseat Formation (lower Paleocene: Danian) has yield-ed three taxa: Taphrosphys sulcatus (Leidy), Agomphus sp., and Osteopygis emarginatus Cope. These faunas, when compared with Late Cretaceous and early Eocene marine turtle faunas, provide valuable insights into the evolu-tionary history of sea turtles from Late Cretaceous through Early Tertiary time. No catastrophic terminal Cretaceous extinction event among sea turtles is indicated by this succession. Rather, strong decline in the late Campanian is followed by modest recovery in the Thanetian and Ypresian. This decline and renaissance closely matches the global pattern of oceanic cooling and warming in Late Cretaceous-early Tertiary time. Turtle remains have been reported from the Aquia Formation of the Pamunkey Group since 1895, but mostly from isolated fragments (for example, see Clark & Martin 1901). Not until Lynn (1929) described a fairly complete carapace of '^ Amy da" vir-giniana was there sufficient material ade-quate to characterize even one species. Even so, Lynn did not demarcate the suture boundaries on this specimen and the pub-lished illustration does not show them clear-ly. Since the publication of Lynn's paper, more chelonian material has turned up spo-radically both in the Aquia Formation and in the underlying Brightseat Formation, but it has not been described. This new mate-rial, although far from ideal, is still sufficient to expand greatly our knowledge of the di-versity and taxonomy of the turtles of Pa-leocene age and sheds new light on their anatomy. Age of the Aquia and Brightseat Forma-tions. —The Aquia formerly was considered to be a lower Eocene unit (Clark & Martin 1901), but Loeblich & Tappan (1957) dem-onstrated that it should properly be consid-ered part of the upper Paleocene column on the basis of its contained planktonic Fora-minifera. Greater refinement in the strati-graphic position of this unit has been achieved by Gibson and others (1980), whose work indicated that the entire Aquia lies within calcareous nannoplankton zones NP5 through NP9. The Aquia is divided into two members (Clark & Martin 1901), a lower member named the Piscataway which lies within NP5 through NP8, and an upper member named the Paspotansa which falls entirely within NP9. This division im-plies that the Piscataway accumulated 60 to 57 Ma and the Paspotansa accumulated 57 to 55 Ma (Fig. 1). Both members of the Aquia belong within the Thanetian Stage of the Paleocene (Hardenbol 8l Berggren 1 978).