Northeast Pacific record of the Cretaceous marine gastropodAtiraand a review of its paleobiogeography

Abstract

The Cretaceous record of the shallow-marine margaritine gastropod genusAtiraStewart, 1927 in the region extending from Vancouver Island, to northern Baja California is studied in detail for the first time. It is represented byA. popenoein. sp. (late Turonian to earliest Campanian),A. ornatissima(Gabb, 1864) (latest Santonian to late Campanian or possibly early Maastrichtian), andA. inornata(Gabb, 1864) (“mid” Maastrichtian), which is the youngest known species ofAtira.Atiraoriginated in the tropical waters of the Tethys Sea in western Europe as early as the Early Cretaceous, possibly during the Hauterivian but was present there by the late Aptian to early Albian. The genus subsequently immigrated to other regions and became adapted to warm-temperate waters. By the late Turonian it had migrated westward to northern California. During the Campanian it reached south Sakhalin and in the earliest Maastrichtian it was present in southwest Japan. AlthoughAtira?nebrascensis(Meek and Hayden, 1856) has been questionably reported from Campanian to “mid” Maastrichtian deposits in the Wyoming area of the Western Interior Basin, this species does not belong in genusAtira.