Homalopoma Carpenter, 1864

Kaim, Andrzej, Jenkins, Robert G. & Hikida, Yoshinori, 2009, Gastropods from Late Cretaceous Omagari and Yasukawa hydrocarbon seep deposits in the Nakagawa area, Hokkaido, Japan, Acta Palaeontologica Polonica 54 (3), pp. 463-490 : 470

Genus Homalopoma Carpenter, 1864

Type species: Turbo sanguinaeus Linné, 1758 , original designation; Recent, Mediterranean.

Discussion.—The concept of Homalopoma unites species having small turbiniform anomphalous shells. The type species has a shell with well developed spiral ornament but some species have only weak spiral ribs (e.g., H. baculum [Carpenter, 1864]) or even smooth shells (e.g., H. laevigatum [Sowerby, 1914]). Similar but consistently much larger are shells of the seemingly closely related Cantrainea Jeffreys, 1883 (see discussion below). Here we include only a strongly ornamented species in Homalopoma while two other, weakly ornamented species are assigned to Cantrainea .

Distribution.— Homalopoma is a species−rich genus with a worldwide distribution. It occurs from shallow water to bathyal depths. Some species of Homalopoma (e.g., H. laevigatum ) are reported from sunken wood off Japan (Okutani 2000). An undescribed species occurs also at hot vent in Mariana Arch (Anders Warén, personal communication 2008). An unnamed fossil species of Homalopoma was reported by Gill et al. (2005) from Eocene–Miocene aged hydrocarbon seep deposits on Barbados and two other unnamed species are reported from two Eocene hydrocarbon seeps of Washington State, USA by Goedert and Squires (1990). Another species, Homalopoma wattsi (Dickerson, 1916) , has been reported by Kiel (2008) from Eocene wood−fall association in Washington State, USA. Abundant occurrences of Homalopoma domeniconii Moroni, 1966 are reported by Moroni (1966) from the Miocene “Calcare a Lucine” in Italy which have been later identified to be seep carbonates ( Taviani 1994; Peckmann et al. 1999). H. abeshinaiensis described below represents the oldest record of Homalopoma reported so far from chemosynthesis−based communities.