Motani Ryosuke, Pyenson Nicholas D, Jiang Da-Yong
Department of Earth and Planetary Sciences, University of California, Davis, Davis, California, United States.
Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, United States.
PeerJ. 2025 Jul 4;13:e19666. doi: 10.7717/peerj.19666. eCollection 2025.
One of the recurring paleobiological questions over the last three decades has been whether there were any filter feeding tetrapods before whales evolved. Recently, a study proposed that a small marine reptile from the Early Triassic, , filter-fed in a mode similar to living right and bowhead whales (Balaenidae). The case for filter feeding was largely based on perceived similarities in dorsal-view cranial morphology between and Balaenidae, analyzed through geometric morphometrics of 2D landmarks. Here, we show that this similarity was an artifact of multiple errors, including the use of a dataset of extant cetaceans that does not match the morphology of respective species. Notably, 15 of the cetacean species examined were represented by narrow skulls reminiscent of ; without these unrealistic data points, has no morphospace overlap with any cetaceans, invalidating the proposed inference for Triassic filter-feeding. We collected a new set of landmarks using the published definitions to see how the result changes when using more accurate data along the original authors' intention. We determined that odontocetes and mysticetes do not overlap in morphospace with , which plots outside any living cetacean species. We conclude that there is insufficient evidence to suggest that was a filter feeder, in concordance with: energetic studies suggesting balaenid-style feeding would be unsustainable at the small body sizes of ; the lack of an intraoral space for the baleen; and the long neck and comparatively small head that are unsuitable for continuous ram feeding to filter prey-laden volumes of water. This re-examination of highlights the challenges for inferring filter-feeding in other extinct tetrapods.
在过去三十年中反复出现的古生物学问题之一是，在鲸鱼进化之前是否存在任何滤食性四足动物。最近，一项研究提出，一种来自早三叠世的小型海洋爬行动物，以类似于现存的露脊鲸和弓头鲸（露脊鲸科）的方式进行滤食。滤食的证据主要基于通过二维地标几何形态测量分析得出的该海洋爬行动物与露脊鲸科在背视颅骨形态上的明显相似性。在这里，我们表明这种相似性是多种错误造成的假象，包括使用了与各物种形态不匹配的现存鲸类数据集。值得注意的是，所检查的15种鲸类物种中有窄头骨，这让人联想到该海洋爬行动物；没有这些不切实际的数据点，该海洋爬行动物与任何鲸类在形态空间上都没有重叠，从而使关于三叠纪滤食的推断无效。我们根据已发表的定义收集了一组新的地标，以了解按照原作者的意图使用更准确的数据时结果会如何变化。我们确定齿鲸类和须鲸类在形态空间上与该海洋爬行动物没有重叠，该海洋爬行动物位于任何现存鲸类物种之外。我们得出结论，没有足够的证据表明该海洋爬行动物是滤食性动物，这与以下观点一致：能量学研究表明，以露脊鲸科的方式进食对于该海洋爬行动物的小体型来说是不可持续的；缺乏用于鲸须的口腔内空间；以及长脖子和相对较小的头部不适合持续冲撞式进食以过滤充满猎物的大量海水。对该海洋爬行动物的重新审视凸显了推断其他已灭绝四足动物滤食行为的挑战。
