tail vertebrae is also marked by a vertebral bend of about 45°, which is the highest possible angle known in extant sharks and is mostly found in fast-swimming sharks, such as lamnids. These properties of the tail, along with other features such as smooth scales parallel to the body axis, a plesodic pectoral fin (a pectoral fin in which cartilage extends throughout, giving it a more secure structure that helps decrease drag), and a spindle-shaped stocky build, show that C. mantelli was capable of fast swimming. Physiology ThermoregulationCretoxyrhina represents one of the earliest forms and possible origins of endothermy in mackerel sharks. Possessing regional endothermy (also known as mesothermy), it may have possessed a build similar to modern regionally endothermic sharks like members of the thresher shark and lamnid families, where red muscles are closer to the body axis compared to ectothermic sharks (whose red muscles are closer to the body circumference), and a system of specialized blood vessels called rete mirabile (Latin for "wonderful nets") is present, allowing metabolic heat to be conserved and exchanged to vital organs. This morphological build allows the shark to be partially warm-blooded, and thus efficiently function in the colder environments where Cretoxyrhina has been found. Fossils have been found in areas where paleoclimatic estimates show a surface temperature as low as . Regional endothermy in Cretoxyrhina may have been developed in response to increasing pressure from progressive global cooling and competition from mosasaurs and other marine reptiles that had also developed endothermy. Hydrodynamics and locomotionCretoxyrhina possessed highly dense overlapping placoid scales parallel to the body axis and patterned in parallel kneels separated by U-shaped grooves, each groove having a mean width of about 45 micrometers. This formation of scales allows efficient drag reduction and enhanced high-speed velocity capabilities, a morphotype seen only in the fastest known sharks. Cretoxyrhina also had the most extreme case of a "Type 4" tail fin, having the highest known Cobb's angle (curvature of tail vertebrae) and tail cartilage angle (49° and 133° respectively) ever recorded in mackerel sharks. A "Type 4" tail fin structure represents a build with maximum symmetry of the tail fin lobes, which is most efficient in fast swimming; among sharks, it is only found in lamnids. A 2017 study by PhD student Humberto Ferron analyzed the relationships between the morphological variables including the skeleton and tail fin of C. mantelli and modeled an average