Feeding without teeth: the material properties of rhamphothecae from two species of durophagous sea turtles.

The feeding apparatus of sea turtles comprises cornified keratinous rhamphothecae overlaying a bony rostrum. Although keratin is less stiff than the enamel of toothed animals, certain species of sea turtles are capable of withstanding large forces when feeding on hard prey. We aimed to quantify the mineral density, water content and compressive mechanical properties of rhamphothecae from two durophagous species: loggerhead () and Kemp's ridley () sea turtles.

Puncture performance tests reveal distinct feeding modes in pinniped teeth.

Marine mammals have undergone a dramatic series of morphological transformations throughout their evolutionary history that facilitated their ecological transition to life in the water. Pinnipeds are a diverse clade of marine mammals that evolved from terrestrial carnivorans in the Oligocene (∼27 million years ago). However, pinnipeds have secondarily lost the dental innovations emblematic of mammalian and carnivoran feeding, such as a talonid basin or shearing carnassials.

Caudal Spine Morphology and Puncture Performance of Two Coastal Stingrays.

A diagnostic characteristic of stingrays in the family Dasyatidae is the presence of a defensive, partially serrated spine located on the tail. We assessed the contribution of caudal spine morphology on puncture and withdrawal performance from two congeneric, co-occurring stingrays, the Atlantic stingray, Hypanus sabinus, and the bluntnose stingray, Hypanus say. Spines exhibited a high degree of morphological variability.

Two heads are not always better than one: Craniofacial and axial bifurcation in cheloniid embryos and hatchlings (Chelonia mydas and Caretta caretta).

Morphological data on craniofacial and axial bifurcation in sea turtles is not well documented in the literature. Here, we use micro-computed tomography (μ-CT) imaging to describe the body, skull, and vertebral morphology in axially-bifurcated cheloniid sea turtle embryos and hatchlings (Chelonia mydas and Caretta caretta) from south Florida beaches. We describe three types of craniofacial and axial bifurcations: bifacial, bicephalic, and bicephalic with biaxial duplication ranging from facial bones to the sacrum.

Microarchitecture of cetacean vertebral trabecular bone among swimming modes and diving behaviors.

Cetaceans (dolphins, whales, and porpoises) are fully aquatic mammals that are supported by water's buoyancy and swim through axial body bending. Swimming is partially mediated by variations in vertebral morphology that creates trade-offs in body flexibility and rigidity between axial regions that either enhance or reduce displacement between adjacent vertebrae. Swimming behavior is linked to foraging ecology, where deep-diving cetaceans glide a greater proportion of the time compared to their shallow-diving counterparts.

Developmental changes in bone mechanics from Florida manatees (), obligate swimming mammals.

Mammals living in aquatic environments load their axial skeletons differently from their terrestrial counterparts. The structure and mechanical behavior of trabecular bone can be especially indicative of varying habitual forces. Here, we investigated vertebral trabecular bone mechanical properties (yield strength, stiffness and toughness) throughout development in Florida manatees (), obligate undulatory swimmers.

Mechanical behavior of shark vertebral centra at biologically relevant strains.

Cartilaginous shark skeletons experience axial deformation at the intervertebral joints, but also within the mineralized cartilaginous centrum, which can compress to between 3% and 8% of its original length in a free-swimming shark. Previous studies have focused on shark centra mechanical properties when loaded to failure; our goal was to determine properties when compressed to a biologically relevant strain. We selected vertebrae from six shark species and from the anterior and posterior regions of the vertebral column.