Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA.
Department of Marine Biology, Texas A&M University, Galveston, TX, USA.
Sci Rep. 2022 Jul 6;12(1):11448. doi: 10.1038/s41598-022-15684-8.
Today's mysticetes filter-feed using baleen, a novel integumentary structure with no apparent homolog in any living mammal. The origins of filter-feeding and baleen can be informed by the fossil record, including rare instances of soft tissue preservation of baleen and also by potential osteological correlates of baleen. Lateral palatal foramina on the roof of the mouth have been proposed as potential osteological correlates of baleen and their presence in some tooth-bearing stem mysticetes has led to the hypothesis that these early mysticetes possessed both teeth and incipient baleen. Here, we test this hypothesis by examining lateral palatal foramina in both filter-feeding and non-filter-feeding cetaceans, including crown and stem odontocetes and in stem cetaceans (or archaeocetes). We also confirm the presence of lateral palatal foramina in 61 species of terrestrial artiodactyls. CT scanning demonstrates consistent internal morphology across all observed taxa, suggesting that the lateral palatal foramina observed in extant mysticetes are homologous to those of terrestrial artiodactyls. The presence of lateral palatal foramina in terrestrial artiodactyls and non-filter-feeding whales (odontocetes and archaeocetes) suggests that these structures are not unique predictors for the presence of baleen in fossil whales; instead, these structures are more probably associated with gingiva or other oral tissue.
现今的须鲸类通过鲸须滤食，鲸须是一种独特的表皮结构，在现存的任何哺乳动物中都没有明显的同源物。滤食和鲸须的起源可以通过化石记录来了解，包括鲸须的软组织保存的罕见实例，以及鲸须的潜在骨骼学相关性。口腔顶部的侧腭孔被认为是鲸须的潜在骨骼学相关性，在一些有齿的原始须鲸类中存在这些孔，导致了这些早期须鲸类同时拥有牙齿和初期的鲸须的假说。在这里，我们通过检查滤食和非滤食鲸类（包括齿鲸和原鲸类）以及原鲸类（或古鲸类）的侧腭孔，来检验这一假说。我们还证实了 61 种陆生偶蹄类动物中存在侧腭孔。CT 扫描显示所有观察到的分类群的内部形态一致，这表明现存须鲸类的侧腭孔与陆生偶蹄类动物的侧腭孔是同源的。侧腭孔在陆生偶蹄类动物和非滤食性鲸类（齿鲸和古鲸类）中的存在表明，这些结构并不是化石鲸类中存在鲸须的唯一预测因子；相反，这些结构更可能与牙龈或其他口腔组织有关。
