Lateral palatal foramina are ubiquitous across fossil whales and shared with hippos

Abstract

Lateral palatal foramina have been proposed as osteological correlates for baleen in fossil mysticetes. A recent study reported significantly elevated foramina counts in extant mysticetes relative to terrestrial artiodactyls (Ekdale et al. 2024 Sci. Rep. 14, 10174 (doi:10.1038/s41598-024-60673-8)). However, that analysis drew conclusions about fossil taxa despite not including any fossil taxa in its analysis. Here, we merge the datasets of Peredo et al. (Peredo et al. 2022 Sci. Rep. 12, 11448 (doi:10.1038/s41598-022-15684-8)) and Ekdale et al. (Ekdale et al. 2024 Sci. Rep. 14, 10174 (doi:10.1038/s41598-024-60673-8)) and add palatal foramina counts for eight stem mysticetes, producing a combined dataset of 195 specimens. Stem mysticetes are statistically indistinguishable from terrestrial artiodactyls in the number of palatal foramina (stem mysticete median = 4; artiodactyl median = 3) and significantly different from extant mysticetes (median = 46.5). Finer taxonomic analysis reveals that the elevated mysticete signal is driven by Balaenopteroidea. Balaenidae and Neobalaenidae, despite bearing baleen, do not exhibit elevated counts. Moreover, the elevated counts in Balaenopteroidea are a condition shared with Hippopotamidae, the closest living relatives of cetaceans. These results indicate that palatal foramina counts probably reflect the degree of soft tissue vascularization rather than the presence of baleen. Lateral palatal foramina counts cannot be used to infer baleen in fossil whales, and phylogenetic bracketing remains the most defensible framework for inferring baleen in fossil cetaceans.