Early Miocene marine ostracods from southwestern India: implications for their biogeography and the closure of the Tethyan Seaway

Twenty-six genera and 34 species of early Miocene Indian shallow-marine ostracods were examined for taxonomy and paleobiogeography. A new genus Paractinocythereis and new species Costa ponticulocarinata were described. Early Miocene Indian ostracod fauna shows strong affinity to Eocene–Miocene Eastern and Western Tethyan ostracod faunas and Miocene–Recent Indo-Pacific ostracod fauna, supporting the Hopping Hotspot Hypothesis that Tethyan biodiversity hotspot have shifted eastward through Arabia to Indo-Australian Archipelago (IAA) together with concomitant biogeographic shifts of the Tethyan elements. The result also indicated an inverse westward distributional shift in a genus. It is important to note that Paleogene and Miocene shallow-marine ostracods from the IAA region remain poorly investigated, and more fossil ostracod data is needed to better test the Hopping Hotspot Hypothesis.本研究针对26属34种早中新世印度浅海介形类（Ostracods）开展了分类学与古生物地理学研究。本次研究建立了1个新属Paractinocythereis以及1个新种Costa ponticulocarinata。早中新世印度介形虫动物群与始新世—中新世东、西特提斯介形虫动物群以及中新世—现代印度-太平洋介形虫动物群具有高度亲缘关系，该结果支持跳跃热点假说（Hopping Hotspot Hypothesis）：特提斯生物多样性热点经阿拉伯半岛向东迁移至印度-澳大利亚群岛（Indo-Australian Archipelago, IAA），同时伴随特提斯类群的生物地理分布偏移。本研究同时发现某一属群存在反向的向西分布迁移现象。值得注意的是，目前印度-澳大利亚群岛区域的古近纪与中新世浅海介形类研究仍较为匮乏，未来需要更多化石介形类数据以更好地验证跳跃热点假说。