Sirenko Boris
Zoological Institute, Russian Academy of Sciences, Universitetskaya nab.199034, St. Petersburg, Russia.; Email:
Zootaxa. 2015 Oct 22;4033(2):151-202. doi: 10.11646/zootaxa.4033.2.1.
The Southeast region off Chile and Peru has yielded a very rich diverse fauna of basal chitons of the genus Leptochiton. The present contribution is based on the study of 1055 specimens of chitons. Thirteen leptochitonid species are reported of which seven species are new, namely Leptochiton lascrusesi n. sp., L. linseae n. sp., L. longibranchiae n. sp., L. peruvianus n. sp., L. macleani n. sp., L. sigwartae n. sp., and L. mutschkeae n. sp. Five species were found on the shelf, but only one of those is limited to this zone. The other eight species live in bathyal or abyssal depths. Thus, 12 of 13 species were found deeper than 200 m. The genus Leptochiton originated in the late Palaeozoic in shallow waters. It probably shifted to deep-waters because of competition by more advanced genera of chitons. The leptochitonid fauna of the Peru-Chile Trench turned out to be rich. Five species were studied from this trench system. Two of them-L. longibranchiae n. sp. and L. peruvianus n. sp.-are characterized by an unusually high number of gills and an accordingly wider distribution in the mantle cavity, reaching in an anterior direction to valves V and III. This morphological peculiarity is unusual for Lepidopleurida and resembles the conditions found in the order Chitonida.
智利和秘鲁沿岸的东南部地区产出了非常丰富多样的薄石鳖属（Leptochiton）基干石鳖动物群。本研究基于对1055个石鳖标本的研究。报告了13种薄石鳖科物种，其中7种为新物种，即拉氏薄石鳖（Leptochiton lascrusesi）新种、林氏薄石鳖（L. linseae）新种、长鳃薄石鳖（L. longibranchiae）新种、秘鲁薄石鳖（L. peruvianus）新种、麦克利薄石鳖（L. macleani）新种、西格瓦特薄石鳖（L. sigwartae）新种和穆茨克薄石鳖（L. mutschkeae）新种。在陆架上发现了5个物种，但其中只有1个物种局限于该区域。其他8个物种生活在半深海或深海深度。因此，13个物种中有12个在深度超过200米处被发现。薄石鳖属起源于古生代晚期的浅水区。由于更进化的石鳖属的竞争，它可能转移到了深水区。秘鲁-智利海沟的薄石鳖科动物群很丰富。从这个海沟系统中研究了5个物种。其中两个——长鳃薄石鳖新种和秘鲁薄石鳖新种——的特征是鳃的数量异常多，相应地在鳃腔中的分布更宽，向前延伸到第V和第III块壳板。这种形态特征在鳞侧石鳖目（Lepidopleurida）中是不寻常的，类似于石鳖目（Chitonida）中发现的情况。
