Over the last 250 million years, many different animal groups have independently evolved adaptations to living in water. For predators, the functional demands of aquatic life necessitated changes to prey capture, leading to the evolution of new feeding styles and anatomy. Canine teeth are essential tools for feeding, and in terrestrial carnivores, there are well-established links between their form and function. However, we do not know if these patterns hold in aquatic mammals, such as otters or seals.
We undertook a combined analysis of canine tooth shape and biomechanics in a sample of 215 teeth representing a broad range of terrestrial, semi-aquatic, and aquatic mammals. First, we used geometric morphometrics to quantify tooth shape, then tested for associations between shape and feeding style. Next, we assessed the biomechanics underlying these associations, undertaking finite element analyses to model stress and physical puncture tests to quantify puncture force. Shape analysis indicates that suction feeders have robust and curved canines, while raptorial species have straighter, thinner canines. Biomechanical testing demonstrates that raptorial species canines penetrate more easily but are more fragile than those of suction-feeders. These patterns can aid in understanding the feeding biology of difficult-to-observe and extinct marine species.