Mandarina ogasawarana

[Melanie]

A new fossil species of the pulmonate genus Mandarina Pilsbry, 1894, Mandarina ogasawarana, is described on the basis of specimens collected from Holocene dune deposits(2000yr B.P.) on Hahajima in the Bonin Islands of the western Paficic. The distribution of the new species is restricted to the Hyogidaira and Nakanodaira areas of Hahajima. The new species is similar to Mandarina aureola Chiba. 1989 and M. polita Chiba, 1989, but can easily be distinguished from the latter two species by apertural morphology and color polymorphisms. M. ogasawarana sp. nov. and M. aureola are found in the same locality and bed, suggesting that both species were reproductively isolated from each other at that time. The fossil record and 14C dating indicate that M. ogasawarana became extinct after 2000yr B.P. on Hahajima. Although the cause of the extinction of M. ogasawarana is still speculative, this species would have been vulnerable to extinction more than other species because of its small and restricted distribution range. (author abst.)

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