Quantifying the Morphological Differences Between Fur Seals and Sea Lions

The eared seals (family Otariidae) are divided into fur seals and sea lions, despite a lack of cladistic support for these groups. The division is primarily based on hair morphology, and it is unknown whether any other morphological signal differentiates these two groups. In this study, 3D geometric morphometric analyses were used to investigate differences in cranial shape between fur seals and sea lions. A total of 50 3D cranial scans were analyzed using 3D geometric morphometrics, accounting for variation by sex and phylogenetic relationships. Non‐phylogenetic analyses identified significant morphological differences between fur seals and sea lions, and males and females, independent of allometry. However, phylogenetic analyses found only female fur seals and sea lions differed in cranial shape, which was explained by allometry. Fur seals possessed less disparate cranial morphology, whereas sea lions exhibited greater morphological variability. These findings suggest that allometry affects morphological signals in fur seals and sea lions.