The gastropod family Atlantidae is a group of holoplanktonic mollusks comprising 23 species in three genera. Most atlantids have tropical and subtropical affinity, but two thirds of the known species are also distributed in transitional and/or temperate regions. The region off the Baja California Peninsula (BCP) is a faunistic transitional area in which a mix of subarctic, temperate, subtropical, and tropical communities occurs. Since the last extensive study in 1967, only eight species of Atlantidae have been recorded. In this study, the atlantid species composition off the BCP was determined based on three oceanographic surveys in fall 2015, winter, and spring 2016. A total of 18 species were recorded. The findings of Atlanta brunnea J.E. Gray, 1850, A. echinogyra Richter, 1972, A. frontieri Richter, 1993, A. gibbosa Souleyet, 1852, A. helicinoidea J.E. Gray, 1850, A. plana Richter, 1972, A. tokiokai van der Spoel & Troost, 1972 and Oxygyrus inflatus Benson, 1835 represent northward expansion of their known distributional range, while A. fragilis Richter, 1993 and A. rosea Gray, 1850 are recorded for the first time in the American Pacific, thus increasing to 20 the number of species present in the Northeastern Pacific region. These records allow the recognition of the Pacific coast off the BCP as an area of high species diversity of atlantids in the Mexican Pacific.

中文翻译：

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来自墨西哥南部下加利福尼亚州半岛的加利福尼亚南部地区的亚特兰软体动物（Gastropoda：Pterotracheoidea）的多样性

腹足纲动物亚纲科是一组完整的浮游软体动物，包括三个属的23个物种。大多数Atlantids具有热带和亚热带的亲和力，但是三分之二的已知物种也分布在过渡和/或温带地区。下加利福尼亚州半岛（BCP）以外的地区是一个充满泥炭纪的过渡地区，这里混合了北极，温带，亚热带和热带群落。自1967年进行最后一次广泛研究以来，仅记录了8种亚特兰科。在这项研究中，根据2015年秋季，冬季和2016年春季的三项海洋学调查，确定了BCP附近的大西洋物种组成。总共记录了18种。亚特兰大brunnea的发现JE Gray，1850年，A。echinogyra Richter，1972年，A. frontieri Richter，1993，A. gibbosa Souleyet，1852，A. helicinoidea JE Gray，1850，A. Plana Richter，1972，A. tokiokai van der Spoel＆Troost，1972和Oxygyrus inflatus Benson，1835代表其向北扩展已知的分布范围，而美洲太平洋地区首次记录了脆弱的A. fragilis Richter（1993年）和玫瑰色的A. rosea Gray（1850年），因此东北太平洋地区的物种数量增加到20种。这些记录使人们认识到BCP附近的太平洋海岸是墨西哥太平洋atlantids物种高度多样性的地区。