310 Paleogene marine gastropods of the Keasey Formation in Oregon

Paleogene marine gastropods of the Keasey Formation in Oregon - BAP #310

Abstract:

Sixty-eight gastropods species (8 archaeogastropods, 20 mesogastropods, 37 neogastropods, 3 opisthobranchs) are described and illustrated from the late Eocene to early Oligocene bathyal mollusk fauna of the Keasey Formation in northwestern Oregon, and time-equivalent beds in southwestern Washington. Twenty-three species are described as new: Acmaea vokesi, Bathybembix nitor, Margarites (Margarites) sericeus, Solariella (Machaeroplax) cicca, Turritella keaseyensis, Epitonium (Boreoscala) wyattdurhami, “Fusitriton” terrysmithae, Fulgurofusus serratus, Trophonopsis platacantha, Colus ? precursor, Fusinus dilleri, Exilia bentsonae, Conomitra vernoniana, Ancilla (Spirancilla) vernisa, Granula profundorum, Bonellitia (Bonelletia) smithwickensis, Bonelletia (Admetula) tumida, sveltella exiliplex, Sveltella ? keaseyensis, “Admete” umbilicate, conus weltoni, Conus armentrouti, and Scaphander impunctatus.  

            Two recurring bathyal gastropod association types are represented in the Keasey Formation: one a species-dominant association type characterized by numerous large-shelled trochids of the genus Bathybembix s. l., and the other a species-diverse association type containing as many as seven species of turrid gastropods.

            Abrupt global changes that have been documented in marine faunal composition at approximately 38 m. y. BP are recognized in the numerous generic and species level extinctions and appearances at the onset of Keasey deposition.

            Detailed biostratigraphic distributions of gastropod species reveal four stratigraphically distinct associations and support four-fold faunal subdivision of the formation.

C.S. Hickman