Supplementary Table S7 from Ancient whales did not filter feed with their teeth

The origin of baleen whales (Mysticeti), the largest animals on Earth, is closely tied to their signature filter-feeding strategy. Unlike their modern relatives, archaic whales possessed a well-developed, heterodont adult dentition. How these teeth were used, and what role their function and subsequent loss played in the emergence of filter feeding, is an enduring mystery. In particular, it has been suggested that elaborate tooth crowns may have enabled stem mysticetes to filter with their postcanine teeth in a manner analogous to living crabeater and leopard seals, thereby facilitating the transition to baleen-assisted filtering. Here we show that the teeth of archaic mysticetes are as sharp as those of terrestrial carnivorans, raptorial pinnipeds and archaeocetes, and thus were capable of capturing and processing prey. By contrast, the postcanine teeth of leopard and crabeater seals are markedly blunter, and clearly unsuited to raptorial feeding. Our results suggest that mysticetes never passed through a tooth-based filtration phase, and that the use of teeth and baleen in early whales was not functionally connected. Continued selection for tooth sharpness in archaic mysticetes is best explained by a feeding strategy that included both biting and suction, similar to that of most living pinnipeds and, probably, early toothed whales (Odontoceti).作为地球上现存体型最大的动物类群，须鲸类（Mysticeti）的起源与其标志性的滤食摄食策略紧密相关。与现生近亲不同，古鲸类拥有发育完备的成年异型齿列。这类牙齿曾被如何利用，以及其功能与后续的牙齿丢失过程在滤食行为的起源中发挥了何种作用，始终是学界长期关注的未解之谜。此前有研究提出，复杂的齿冠结构或许让须鲸干群能够借助后犬齿开展滤食，其机制与现生食蟹海豹和豹形海豹的滤食方式类似，进而推动了向须鲸辅助滤食的演化过渡。本研究表明，古须鲸类的牙齿与陆生食肉目动物、掠食性鳍足类以及古鲸亚目（Archaeocetes）的牙齿同样锋利，因此具备捕获并处理猎物的能力。与之形成显著反差的是，豹形海豹与食蟹海豹的后犬齿明显更为钝厚，完全不适用于掠食性摄食。我们的研究结果显示，须鲸类从未经历过以牙齿为核心的滤食阶段，早期鲸类对牙齿与须鲸的功能使用并不存在关联。古须鲸类中持续存在的牙齿锋利性选择压力，最合理的解释是其摄食策略同时涵盖了撕咬与吸食行为，这与现生多数鳍足类以及早期齿鲸类（Odontoceti）的摄食模式高度相似。