, an extant reptile with a sail on its back Varying suggestions have been made for the function of the sail.
Thermoregulation The structure may have been used for
thermoregulation. The base of the spines have a channel which may have contained a
blood vessel supplying abundant blood to the sail. The animal could have used the sail's large surface area to absorb heat from the sun in the morning. As
ectotherms they required heat from an external source before their muscles would start to function properly. A predator would thus have an advantage over its slower moving prey. The sail could be used in reverse if the animal was overheating. By standing in the shade, the sail would radiate heat outwards. However, recent studies have put in doubt the efficiency of this purported means of thermoregulation, and indeed no extinct sailed animal is currently assumed to have used its sails for thermoregulation.
Sexual selection Elaborate body structures of many modern-day animals usually serve to attract members of the opposite sex during
mating. This has been proposed as one potential function of the sail. and by Jack Bowman Bailey in 1997.
Camouflage Dimetrodon may have used the sail on its back to help
camouflage itself when hiding among reeds and waiting to
ambush its prey.
Sound display Gregory Paul argued that parallel neck sails of
Amargasaurus would have reduced neck flexion. Instead, he proposed that, with their circular rather than flat cross-sections, these spines were more likely covered with a
horny sheath. He also suggests that they could have been clattered together for a sound display. In 2022, a detailed study was published by Cerda
et al. analyzing the structure, morphology, and microanatomy of the vertebral spines of
Amargasaurus. They suggested that the spines were not covered in a keratinous sheath as previously believed. Osteohistology of the spines suggests that they were likely, if not exclusively, covered in a sail of skin. The spines are also highly vascularized and bear cyclical growth marks, adding credence to this theory. ==List of organisms with a sail==