How do vertebral and craniocervical features of Common bottlenose dolphin Tursiops truncatus and Harbour porpoise Phocoena phocoena influence physiological and behavioral traits

The aim of this study was to understand the physiological and behavioral characteristics of the bottlenose dolphin ( Tursiops truncatus ) and the harbour porpoise ( Phocoena phocoena ) by comparing their vertebral and craniocervical features. The neck of the harbour porpoise is more restricted than that of the bottlenose dolphin, but the skull itself has a larger articulation capacity. The skull of the bottlenose dolphin is supported by a larger surface area of the atlas, which may support the use of the skull as a hammer or mace for hunting and attacking. Epiphyseal ossification is present in all vertebrae of the harbour porpoise and between L21 and L27 in the bottlenose dolphin. The maximum corpus thickness, indicating the center of gravity, peaks at Ca14 in the bottlenose dolphin and forms a flat plateau of approximately equal between the L11-Ca10 in the harbour porpoise, suggesting that the former has adapted to swim largely by tail-flapping, which requires more energy and allows faster swimming, but the latter can optionally use both a low-energy, slow swimming style of belly flapping and a high-energy, fast swimming style of tail-flapping. The foramen vertebrae are much larger in the proximal part of the thoracal vertebrae of the Bottlenose dolphin, indicating stronger spinal cord activity around the pectoral fins, which may explain stronger and finer maneuverability. Vertebral anatomy in delphinid cetaceans is relatively well-defined, showing heterogeneity; therefore, larger sample sizes are needed to confirm whether these observations and hypotheses apply to the individuals or species studied.