A Mactrid Bivalve from Pleistocene Deposits of Lake Russell, Mono Basin, California

Rangia des Moulins, 1832 is a small genus of mactrid bivalves that is currently distributed in estuarine waters of the eastern United States, Gulf of Mexico, and Gulf of California (Keen, 1971; Abbott, 1974). (One congener, R. cuneata [Sowerby, 1831], was recently introduced to the Antwerp (Belgium) harbor [Verween et al., 2006].) Although these clams are euryhaline and capable of living in freshwater as adults, they require an estuarine-like salinity regime for successful reproduction and recruitment (Cain, 1973; Hopkins et al., 1974), which has constrained their ability to penetrate the North American continental interior through coastal drainages (Cain, 1974; Swingle and Brand, 1974). the Neogene and Quaternary fossil record of the genus is also restricted to coastal or near-coastal marine-influenced depositional systems, with the exception of Holocene specimens of R. cuneata from two archeological sites in the central United States which were obviously introduced by humans (Baker, 1941; Hill, 1983), and a Pleistocene(?) occurrence of this species from along the Pecos River in New Mexico (more than 800 km from the sea) which has been attributed to transport of Gulf Coast immigrants on waterfowl (Metcalf, 1980; Taylor, 1985). Here we provide fossil evidence that the biogeographic history of this predominantly brackish-coastal genus also includes avian-assisted colonization of a far inland lake in the western United States—Pleistocene Lake Russell, Mono Basin, California (Fig. 1).