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| Xenassiminea nana Fukuda, 2023 |
ABSTRACT
Xenassiminea nana n. gen. and n. sp. is described from estuaries of temperate mainland Japan (central to western Honshū, Shikoku and Kyūshū). This species has a minute, colourless, translucent, depressed and helicoid shell and resembles some so-called skeneimorphs. However, the anatomical characters of the head–foot, radula and reproductive system indicate that this species belongs to the Assimineidae, in spite of the dissimilarity in shell features. The presence of basal cusps of the central radular teeth and the extremely rudimentary cephalic tentacles indicate that it should be assigned to the subfamily Assimineinae. The shell size (0.8 mm in length, 1.1 mm in diameter) is the smallest among known assimineids. It lives beneath stones deeply buried in sandy mud flats at the innermost parts of large bays and can be regarded as threatened by the rapid loss of these habitats in recent years.
KEYWORDS: Anatomy, conservation, description, estuary, new species, salt marsh, taxonomy, tidal flats, vulnerable species, Xenassiminea nana
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| Xenassiminea nana a novel, rare, molluscan species with a translucent, spiral shell, discovered in mainland Japan. |
Hiroshi Fukuda. 2023. A New Genus and Species of the Assimineidae (Caenogastropoda: Truncatelloidea) from temperate mainland Japan. Molluscan Research. DOI: 10.1080/13235818.2023.2278070
福田 宏：日本本土温帯域産カワザンショウ科（新生腹足類：クビキレガイ上科）の新属新種
和文摘要: 本州中〜西部・四国・九州の河口域から Xenassiminea nana n. gen. and n. sp. カハタレカワザンショウを記載する。この種の殻は微小・無色半透明・螺塔低平な蝸牛形でいわゆるシタダミ様を呈するが, 頭部−腹足・歯舌・生殖器などの解剖学的特徴はカワザンショウ科に属すことを示す。歯舌中歯に下歯尖を持ち, 頭触角が極端に短いことからカワザンショウ亜科の一員である。殻の大きさ（殻長0.8 mm, 殻径1.1 mm）はカワザンショウ科の全既知種中で最小である。大規模な内湾最奥部の砂泥干潟に深く埋もれた転石下に棲み, 近年は棲息環境の急速な消失によって危機に瀕していると見做される。
