Meeting Abstract
Marine mammals represent textbook examples of macroevolutionary change to facilitate their transition to life in the water. Carnivorous marine mammals, such as cetaceans and pinnipeds, have dramatically altered their feeding strategies relative to their terrestrial ancestors. Both clades independently lose mastication, a hallmark of mammalian feeding, and there are numerous examples of individual lineages within each clade independently converging on specific feeding modes (i.e. suction feeding, filter feeding, raptorial feeding). However, understanding the breadth of morphological changes associated with these shifts in feeding strategy has proved elusive, largely because feeding ecology cannot be observed for fossils. Here, we examine the relationship between the orientation of the orbit, measured as a deflection from the sagittal plane, and distinct feeding strategies in modern marine mammals with known feeding ecologies. In the extant walrus, Odobenus rosmarus,extreme lateral deflection of the orbits correlates with the evolutionary transition from raptorial to benthic suction feeding in this lineage. Similar patterns are observed in certain cetacean lineages that more exclusively rely on benthic suction feeding, suggesting that raptorial feeding selects for anteriorly oriented orbits. This suggests that the morphology of sensory systems, such as the orientation of the orbit, may be informative for predicting the feeding ecology of fossil marine mammals.
