Serradonta Okutani, Tsuchida, and Fujikura, 1992

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 : 467-469

Genus Serradonta Okutani, Tsuchida, and Fujikura, 1992

Type species: Serradonta vestimentifericola Okutani, Tsuchida, and Fujikura, 1992 , by monotypy; Recent , Sagami Bay, Japan .

Discussion.—The most striking shell character of Serradonta delimiting this genus from other acmaeids is the strongly elongated and compressed shell that is an adaptation for life on vestimentiferan tubes (Okutani et al. 1992; Sasaki et al. 2003). The uneven aperture is caused by this way of attachment to the narrow and rounded substrate.

Similar adaptations are known from other limpets both from hydrothermal vents as well as normal environments. Some lepetodrilid limpets have somewhat compressed shells when they live attached to tubeworms at hydrothermal vents ( Desbruyères et al. 2006). Some lepetellids living on empty polychaete tubes secrete shells of similar shape ( Verrill 1880) while some neolepetopsids are reported to change their shell shape after changing substrate from mussel shells to worm tubes ( Warén and Bouchet 2009). The lottiid limpet Flexitectura from the Ukrainian Miocene ( Anistratenko and Anistratenko 2007) has a very similar shell shape to Serradonta , apparently as an adaptation for life on bryozoan branches (compare Anistratenko and Anistratenko 2007). Undoubtedly, limpets acquired such an adaptation several times. Serradonta is confined to the region of Japanese Islands and this narrow geographic distribution and ecological occurrence suggest that the Recent and fossil species belong to the same genus.

Stratigraphic and geographic range.—Recent hydrocarbon seeps off Japan. Upper Cretaceous hydrocarbon seep deposits in Japan.