Caecidae (Mollusca: Gastropoda) from late Miocene exposures of the “Imperial” Formation in Riverside County, California

Abstract

Three Caecidae species from two genera have been recovered from the late Miocene "Imperial" Formation exposed in Super Creek, north and slightly east of Whitewater, Riverside County, southern California. These specimens record the first fossil Caecidae from California older than Pleistocene. The three taxa are Caecum brasilicum de Folin, 1874, Meioceras nitidum (Stimpson, 1851), and a new species of Caecum named C. roederi n. sp., in honor of friend and colleague Mark Roeder. Caecum brasilicum and M. nitidum occur today in the central-western Atlantic Ocean and their previous fossil occurrences are also there. The occurrence of these Atlantic species in the "Imperial" Formation is not surprising as > 8% of the Super Creek fauna has a Caribbean origin at the species level because of the then submerged Panama seaway that allowed water from the western Atlantic to flow freely into the eastern Pacific.