Department of Geosciences, Eberhard Karls Universität Tübingen, Hölderlinstraße 12, 72074, Tübingen, Germany.
Department of Geology, Faculty of Science, Center of Excellence in Morphology of Earth Surface and Advanced Geohazards in Southeast Asia (MESA CE), Chulalongkorn University, Bangkok, 10330, Thailand.
Sci Rep. 2023 Jul 13;13(1):10406. doi: 10.1038/s41598-023-36559-6.
Fossil Alligator remains from Asia are critical for tracing the enigmatic evolutionary origin of the Chinese alligator, Alligator sinensis, the only living representative of Alligatoridae outside the New World. The Asian fossil record is extremely scarce and it remains unknown whether A. sinensis is an anagenetic lineage or alternatively, extinct divergent species were once present. We provide a detailed comparative description of a morphologically highly distinct Alligator skull from the Quaternary of Thailand. Several autapomorphic characters warrant the designation of a new species. Alligator munensis sp. nov. shares obvious derived features with A. sinensis but autapomorphies imply a cladogenetic split, possibly driven by the uplift of the southeastern Tibetan plateau. The presence of enlarged posterior alveoli in Alligator munensis is most consistent with a reversal to the alligatorine ancestral condition of having crushing dentition, a morphology strikingly absent among living alligatorids. Crushing dentition has been previously considered to indicate an ecological specialisation in early alligatorines that was subsequently lost in Alligator spp. However, we argue that there is yet no evidence for crushing dentition reflecting an adaptation for a narrower niche, while opportunistic feeding, including seasonal utilisation of hard-shelled preys, is a reasonable alternative interpretation of its function.
来自亚洲的鳄鱼化石对于追溯中国扬子鳄的神秘进化起源至关重要，扬子鳄是唯一生活在新世界以外的鳄科动物。亚洲的化石记录极其稀少，目前尚不清楚扬子鳄是否是一个进化支系，或者是否曾经存在灭绝的分支物种。我们提供了一个来自泰国第四纪的形态上高度独特的鳄鱼头骨的详细比较描述。几个独特的特征证明了一个新物种的存在。新种曼氏扬子鳄与扬子鳄有明显的衍生特征，但独特的特征暗示了一个分支分裂，可能是由青藏高原东南部的隆起驱动的。曼氏扬子鳄后牙窝的增大与具有压碎齿的鳄形目祖先状态最为一致，而这种形态在现存的鳄科动物中明显缺失。压碎齿以前被认为是早期鳄形目动物的生态特化特征，随后在扬子鳄属中丢失。然而，我们认为，目前还没有证据表明压碎齿反映了对更窄生态位的适应，而机会主义的进食，包括季节性利用硬壳猎物，是其功能的一个合理替代解释。
