Biodiversity Institute, University of Kansas, Lawrence, KS 66045, USA.
Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA.
Biol Lett. 2021 Jun;17(6):20210185. doi: 10.1098/rsbl.2021.0185. Epub 2021 Jun 30.
Bats dispersed widely after evolving the capacity for powered flight, and fossil bats are known from the early Eocene of most continents. Until now, however, bats have been conspicuously absent from the early Eocene of mainland Asia. Here, we report two teeth from the Junggar Basin of northern Xinjiang, China belonging to the first known early Eocene bats from Asia, representing arguably the most plesiomorphic bat molars currently recognized. These teeth combine certain bat synapomorphies with primitive traits found in other placental mammals, thereby potentially illuminating dental evolution among stem bats. The Junggar Basin teeth suggest that the dentition of the stem chiropteran family Onychonycteridae is surprisingly derived, although their postcranial anatomy is more primitive than that of any other Eocene bats. Additional comparisons with stem bat families Icaronycteridae and Archaeonycteridae fail to identify unambiguous synapomorphies for the latter taxa, raising the possibility that neither is monophyletic as currently recognized. The presence of highly plesiomorphic bats in the early Eocene of central Asia suggests that this region was an important locus for the earliest, transitional phases of bat evolution, as has been demonstrated for other placental mammal orders including Lagomorpha and Rodentia.
蝙蝠在进化出有动力的飞行能力后广泛分散，已知最早的化石蝙蝠出现在各大洲的始新世早期。然而，直到现在，亚洲始新世早期的蝙蝠仍然明显缺失。在这里，我们报告了来自中国新疆北部准噶尔盆地的两颗牙齿，属于亚洲已知最早的始新世早期蝙蝠，代表了目前公认的最原始的蝙蝠臼齿。这些牙齿结合了某些蝙蝠的共有特征和其他胎盘哺乳动物的原始特征，因此可能阐明了蝙蝠支系的牙齿进化。准噶尔盆地的牙齿表明，始新世蝙蝠科 Onychonycteridae 的牙齿非常特化，尽管它们的后肢骨骼结构比任何其他始新世蝙蝠都更原始。与始新世蝙蝠科 Icaronycteridae 和 Archaeonycteridae 的进一步比较未能确定后两个类群的明确共有特征，这增加了它们都不是像目前所认为的那样单系的可能性。高度原始的蝙蝠出现在亚洲的始新世早期，这表明该地区是蝙蝠进化最早的过渡阶段的重要中心，这在包括兔形目和啮齿目在内的其他胎盘哺乳动物目中也得到了证明。
