Reptiles :: essays research papers

Reptiles be vertebrate, or backboned animals constituting the break up Reptilia and are characterized by a combination of features, none of which alone could separate every(prenominal) reptiles from all new(prenominal) animals.The characteristics of reptiles are numerous, therefore set up not be explained in great detail in this report. In no special order, the characteristics of reptiles are cold-bloodedness the presence of lungs direct development, without larval forms as in amphibians a teetotal skin with scales but not feathers or hair an amniote egg inside fertilization a three or four-chambered heart two aortic arches (blood vessels) carrying blood from the heart to the body, unlike mammals and birds that only convey one a metanephric kidney twelve pairs of cranial nerves and skeletal features such as limbs with ordinarily five clawed fingers or toes, at least two spinal anaesthesia bones associated with the pelvis, a single ball-and-socket connection at the head-neck joint or else of two, as in advanced amphibians and mammals, and an incomplete or complete sectionalisation along the roof of the mouth, separating the food and air pass climb onways so that breathing can continue while food is being chewed. These and other traditional delineate characteristics of reptiles have been subjected to considerable modification in recent times. The extinct dissipated reptiles, called pterosaurs or pterodactyls, are now thought to have been warm-blooded and cover with hair. Also, the dinosaurs are overly now considered by many authorities to have been warm-blooded. The earliest known bird, archaeopteryx, is now regarded by many to have been a small dinosaur, despite its covering of feathers The extinct ancestors of the mammals, the therapsids, or mammallike reptiles, are also believed to have been warm-blooded and haired. Proposals have been made to reclassify the pterosaurs, dinosaurs, and certain other groups out of the class Reptilia into one or mo re classes of their own. The class Reptilia is divided into 6 to 12 subclasses by different authorities. This includes brisk and extinct species. In addition, a number of these subclasses are completely extinct. The subclasses drive away about 24 orders, but only 4 of these are tranquilize represented by living animals.Of the living orders of reptiles, two arose earlier than the age of reptiles, when dinosaurs were dominant. Tuataras, of the order Rhynchocephalia, are found only on New Zealand islands, whereas the equally ancient turtles, order Chelonia, occur nearly worldwide. The order Crocodilia emerged along with the dinosaurs. Snakes and lizards, order Squamata, are today the most numerous reptile species.