West coast North America record of the Paleogene marine stromboid gastropodRimellaand paleobiogeography of the genus

Abstract

The west coast of North America record of the shallow-marine stromboid gastropod genusRimellaAgassiz, 1841 is restudied for the first time in 90 years. This genus comprises a small group of Paleogene gastropods characterized by having an ornamented fusiform shell, a posterior canal ascending the spire, and simple (non-flared) outer lip.Rimella, whose familial ranking has been inconsistent, is placed here in family Rostellariidae Gabb, 1868, subfamily Rimellinae Stewart, 1927.EctinochilusCossmann, 1889;MacilentosClark and Palmer, 1923;VaderosClark and Palmer, 1923; andCowlitziaClark and Palmer, 1923 are recognized here as junior synonyms ofRimella. Four species are recognized from the west coast of North America: early to middle EoceneRimella macilentaWhite, 1889; early EoceneRimella oregonensisTurner, 1938; middle to late EoceneRimella supraplicata(Gabb, 1864) new combination, of whichRostellaria canaliferGabb, 1864,Cowlitizia washingtonensisClark and Palmer, 1923, andCowlitzia problematicaHanna, 1927 are recognized here as junior synonyms; and late EoceneRimella elongataWeaver, 1912.Rimellawas a warm-water gastropod whose earliest known record is of early Paleocene (Danian) age in Pakistan. Other than the west coast of North America,Rimellais found in Eocene strata in western Europe, Turkey, Egypt, Pakistan, southeastern United States, Panama, Peru, and, to a lesser degree, in Trinidad, Columbia, Java, and New Zealand. Global cooling near the end of the Eocene greatly diminished the genus. Its youngest known occurrences are of early Oligocene age in Germany, Italy, England, and Peru.