The Paleo-Tokyo Bay (Kanto Plateau) that persisted during the transgression periods in the Middle-Late Pleistocene is known for its rich marine fauna that accommodated both the warm and cold water taxa brought by the Kuroshio and Oyashio Currents, respectively. However, little is known on the paleoichthyofauna in this area and the processes shaping the marine ichthyofauna of modern southern Kanto. We used fossil fish otoliths and teeth discovered in the Sha’ana Tuffaceous Sand Member belonging to the Chibanian Miyata Formation, exposed at Sha’ana-dai, Miura City, Kanagawa Prefecture, Japan, to reconstruct the paleoichthyofauna and its associated paleoenvironment and explore the content of fish assemblages during this period. The Sha’ana Tuffaceous Sand Member was composed of upper sandy mud and lower muddy sand horizons at the exposure. A total of 1,675 fish remains were collected from this site, of which 1,389 were assigned to 62 distinct taxa (20 orders, 31 families). The taxonomic composition revealed taxa from various environments, including shallow continental shelf, epi- to meso-pelagic settings, and the majority were from a generally temperate climatic zone. Paleoenvironmental analyses suggested that the fish assemblages were from the continental shelf (approximate depth of 100–200 m) in a temperate sea where both warm Kuroshio and cold Oyashio Currents had an influence on the biota. The analysis also showed that two boreal fishes, namely Clupea pallasii and Theragra chalcogramma, once had a wider distribution that extended to the southwestern areas of the Paleo-Tokyo Bay. This study provides a more complete view of the related paleobiogeography of marine fishes during the Chibanian and is essential for reconstructing the evolutionary processes of the rich ichthyofauna in the southern Kanto.

在晚更新世的海侵时期一直存在的古东京湾（关东高原）以其丰富的海洋动物群而闻名，它们分别容纳了黑潮洋流和御潮潮带来的温水和冷水类群。但是，关于该地区的古鱼科鱼类和形成现代关东南部海洋鱼科鱼类的过程知之甚少。我们使用了在日本神奈川县三浦市Sha'ana-dai暴露的，属于Chibanian Miyata组的Sha'ana凝灰岩砂岩成员中发现的化石鱼耳石和牙齿，来重建古鱼藻类及其相关的古环境，并探索在此期间鱼群的含量。Sha'ana凝灰质砂体由上层砂质泥浆层和下层泥质砂层层组成。从该地点总共收集了1,675条鱼遗体，其中1,389条被分配给62个不同的类群（20个订单，31个科）。分类学组成揭示了来自各种环境的生物分类，包括浅大陆架，上到中上层环境，大多数来自一般的温带气候带。古环境分析表明，鱼群来自温带海域的大陆架（大约100-200 m的深度），温暖的黑潮和寒潮都对生物区系产生了影响。分析还显示，有两种北方鱼类，即 从中上层到中上层，大多数来自温带气候区。古环境分析表明，鱼群来自温带海域的大陆架（大约100-200 m的深度），温暖的黑潮和寒潮都对生物区系产生了影响。分析还显示，有两种北方鱼类，即 从中上层到中上层，大多数来自温带气候区。古环境分析表明，这些鱼类群来自温带海域的大陆架（大约100-200 m的深度），温暖的黑潮和寒潮都对生物区系产生了影响。分析还显示，有两种北方鱼类，即Clupea pallasii和Theragra chalcogramma曾经分布较广，延伸至古东京湾的西南地区。这项研究为Chibanian时期海鱼的相关古生物地理学提供了更完整的观点，对于重建关东南部丰富的ichthyofauna的进化过程至关重要。