来自约旦中部的一件晚白垩纪沧龙化石显示了一个带脚蹼的尾巴，它表明这些蜥蜴会像鲨鱼一样地游泳。这项研究发表在本期Nature Communications上。
沧龙在距今大约9800万年-6600万年前是居支配地位的海洋爬行动物。关于沧龙祖先的冲突理论，再加上化石记录中软组织证据的缺乏以及对沧龙身体构造的不正确描述和重建，导致了这样一个普遍假设：这些爬行动物游泳速度慢。Lindgren及同事分析了具有保存极好的软组织的一个化石材料，发现了一个新月状的尾鳍，与鲸和鱼龙（与海豚相似的海洋爬行动物）的相似。
研究人员通过将该化石的形态与现代鲨鱼做比较得出这样的结论：沧龙能高效率地游泳。该研究还表明，这种特征鲜明的尾巴在占据相似环境的几个类群中是独立演化的（生物谷Bioon.com）。
生物谷推荐的英文摘要
Nature Communications DOI:10.1038/ncomms3423
Soft tissue preservation in a fossil marine lizard with a bilobed tail fin
Johan Lindgren，Hani F. Kaddumi & Michael J. Polcyn
Mosasaurs are secondarily aquatic squamates that became the dominant marine reptiles in the Late Cretaceous about 98–66 million years ago. Although early members of the group possessed body shapes similar to extant monitor lizards， derived forms have traditionally been portrayed as long， sleek animals with broadened， yet ultimately tapering tails. Here we report an extraordinary mosasaur fossil from the Maastrichtian of Harrana in central Jordan， which preserves soft tissues， including high fidelity outlines of a caudal fluke and flippers. This specimen provides the first indisputable evidence that derived mosasaurs were propelled by hypocercal tail fins， a hypothesis that was previously based on comparative skeletal anatomy alone. Ecomorphological comparisons suggest that derived mosasaurs were similar to pelagic sharks in terms of swimming performance， a finding that significantly expands our understanding of the level of aquatic adaptation achieved by these seagoing lizards.
