Question

What are the four types of reptiles?

Answer 1

Reptilia is the third class of the Phylum Chordata and it comprises crawling and creeping animals like crocodiles, turtles, lizards, snakes, etc. They can be classified into four major living clades, namely Crocodilia, Sphenodontia, Squamata and Testudines.

Complete answer:
Reptilia is a large group of animals characterized by scaly and dry bodies, devoid of oil glands. This class of animals can be divided into four living clades. A clade is a group of species that are believed to be descended from the same ancestor. Four such groups belonging to reptiles are:
-Crocodilia: This group of living reptiles include crocodiles, alligators, gharials and caimans. They developed into a distinct order during the mid-Triassic period and have descended from terrestrial reptiles. Species of this order have elongated and structurally reinforced skulls, are oviparous and nurture their offspring.
-Sphenodontia: Sphenodon punctatus and Sphenodon guntheri are the only two living species that belong to this group of reptiles which arose in the early Mesozoic era. These are found only on islands of New Zealand and are commonly called “Tuatara”. Although tuataras look like lizards, they lack external ears which distinguishes them from the other.
-Squamata: This group includes all living snakes and lizards, hence it is the largest extant clade of reptiles. These organisms emerged as a separate group in the late Permian period, from lepidosaurian ancestry.
-Testudines: The members of this group can be easily distinguished from other reptiles, as they have the characteristic bony or cartilaginous shell. Turtles, tortoises and terrapins emerged roughly 200 million years ago. At present 325 extant species can be grouped under this clade.

Note:
While only 2 species of Sphenodon live amongst us, approximately 9,200 species of squamata and 25 species of crocodilia thrive on Earth today.
All reptiles have a 3 chambered heart with 2 atria and one ventricle, except crocodilia which have 4 chambered hearts.