Ad
related to: how do scutes from video for preschoolers free worksheets pdf
Search results
Results From The WOW.Com Content Network
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 ...
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).
Overlying the boney elements are a series of scutes, which are made of keratin and are a lot like horn or nail tissue. In the center of the carapace are five vertebral scutes and out from these are four pairs of costal scutes. Around the edge of the shell are 12 pairs of marginal scutes.
Each scale has an outer surface and an inner surface. The skin from the inner surface hinges back and forms a free area which overlaps the base of the next scale which emerges below this scale. [8] A snake hatches with a fixed number of scales. The scales do not increase in number as the snake matures nor do they reduce in number over time.
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.
Typically, 11 or 12 pairs of marginal scutes rim the carapace. [8] Five vertebral scutes run down the carapace's midline, while five pairs of costal scutes border them. [21] The nuchal scute is located at the base of the head. [21] The carapace connects to the plastron by three pairs of inframarginal scutes forming the bridge of the shell. [21]
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.
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.