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Scutes on a crocodile. Reptile skin is covered with scutes or scales which, along with many other characteristics, distinguish reptiles from animals of other classes. They are made of alpha and beta-keratin and are formed from the epidermis (contrary to fish, in which the scales are formed from the dermis).
The individual scutes as shown above have specific names and are generally consistent across the various species of turtles. Terrestrial tortoises do not shed their scutes. New scutes grow by the addition of keratin layers to the base of each scute. Aquatic chelonii shed individual scutes.
Dermal scutes are also found in the feet of birds and tails of some mammals, and are believed to be the primitive form of dermal armour in reptiles. The term is also used to describe the heavy armour of the armadillo and the extinct Glyptodon , and is occasionally used as an alternative to scales in describing snakes or certain fishes, such as ...
The scales and scutes of birds were thought to be homologous to those of reptiles, [4] but are now agreed to have evolved independently, being degenerate feathers. [ 5 ] [ 6 ] Carcharodontosaurid theropod dinosaur Concavenator , is known to have possessed these feather-derived tarsal scutes.
The "central scutes" extend over the dorsal mid line of the carapace from head to tail, with the "costal scutes" running along each side of the central scutes. The "marginal scutes" run along the outer sides of the shell, and the "nuchal scutes" are found in the area directly behind the turtle's head.
Squamata and Rhynchocephalia form the subclass Lepidosauria, which is the sister group to the Archosauria, the clade that contains crocodiles and birds, and their extinct relatives. Fossils of rhynchocephalians first appear in the Early Triassic, meaning that the lineage leading to squamates must have also existed at the time. [4] [5]
The adult's oval carapace is almost as wide as it is long and is usually olive-gray in color. The carapace has five pairs of costal scutes. In each bridge adjoining the plastron to the carapace are four inframarginal scutes, each of which is perforated by a pore. The head has two pairs of prefrontal scales. These turtles change color as they ...
The articulations with neighboring scutes are located on the ventral side, and the dorsal surface is strongly sculptured while the ventral surface of wings is smooth and contains many small openings. "The scutes have very wide wings and cover practically the whole upper part of the trunk. The tail scutes are narrower, the last of which lack wings.