based on characters Reptiles is divided into Four sub class


Subclass -Anapsida:

1) The skull of Reptiles are made by solid roof.
2) In these Reptiles temporal vacuities are absent in the skull.
3) In these Reptiles the quadrate is articulated with Otic bone.
4) Limbs are strong.
1) Carapace and plastron will form the body covering.
This subclass is divided into two orders.

1) Cotylosauria 2) Chelonia.

Order: Cotylosauria:

1) These Reptiles are extinct.

2) They show complete cranial roof.
3) Pelvic girdle is flat.
4) In these Reptiles Jaws and teeth are poorly developed.
These Reptiles resemble with Labyrinthodont Amphibians.
They became extinct in the triassic period of Mesozoic era.
Ex Seymauria and Lepidosaurus.

Order: Chelonia:

This order includes Turtles and Tortoises.
1) These are Terrestrial or aquatic.

2) Body is covered by shell containing dorsal carapace and ventral plastron.
3) Neck, limbs and tail are covered with scales.
4) They show 4 limbs. pentadactyle are, modified into paddles in aquatic forms.
5) Jaws without teeth.
6) Jaws show horny sheaths,
7) Quadrate is immovably articulate.
8) Nasal opening is single.
9) Unpaired copulatory organs are present.
10) Cloacal opening is longitudinal.
11) These are Oviparous.
Ex :.Thonyx (Soft river terrapin), Testudo (Land tortoise). Chelone (Turtle).

Sub class : Parapsida.

1) This group includes extinct forms.
2) Those forms lived from Triasslac period to cretaceous period.
3) Their skull shows one pair of temporal vacuities. They are supratemporal fossae
Ex, lchthyosaurus, plesiosaurus. 

Subclass 3 : Diapsida.

1) In these Reptiles skull shows two temporal vacuities.
2) Modification of typical diapsid condition is common among these members.
This subclass is divided into two super orders Lëpidosauria and Archosauria.

Super Order: Lepldoauiia

1) These are primitive reptiles.
2) Teeth are present on the palate jaw margins. They are not present in Sockets.
This super order includes two living orders.
1) Rhynchocephalia 2) Squamata.

Order: Rhinchocephaiia :-

1) Teeth are acrodont.

2) The skull shows two vacuities.
3) Quadrate bone is immovable.
4) An epipterygoid bone is present
5) Vertebrae are Amphicoelous..
6) Copulatory organs are absent in this order.
Ex Sphenodon (Newzeàland)

Order : Squamata
This includes Snakes & Lizards.
1) Their body is covered by epidermal scales.
2) Single supra temporaI vacuity is seen in lizards and temporal vacuity Is absent In snakes.
3) Teeth are pleurodont.
4) Usually procoelous vertebrae are present.
5) Transverse cloacal opening is piesent.
6) Male shows a pair of eversible copulatory organs, useful for
This is divided into two suborders.

Sub order: 1) Lacertilia.

1) These are terrestrial, arboreal or burrowing forms.
2) limbs &re pentadactyl and are usually present.
3) Sternum is present.
4) Eyelids are movable.
5) Tympanum is present.
Ex : Calotes, Chamaeleon, Draco, Varanus, Gecko.

Sub order: Ophidia.
This sub order includes snakes.
1) They are terrestrial or aquatic, or arboreal or burrowing forms.
2) Temporal vacuities are absent.
3) limbs and limb girdles are absent.
4) Sternum is absent.
5) Eyelids are absent.
6) Tympanum is absent.
7) Tongue is bifid.

Ex Python , Lycodon, Naja naja, Hydrophis, Viper.

Super order Archosauria

This includes advanced reptiles.

1) Teeth are on jaw margins and are set in muscular sockets.
This super order includes a single living order Crocodilia.

Order -Crocodilia:

1. These are fresh water and predatory forms.

2. Body is covered by an exoskeleton made by horny’ scales & scute.
3. Teeth are thecodont.
4. Quadrate is immovable.
5. Vertebrae are procoelous.
6. Spongy lungs are seen.
7. Longitudinal cloacal opening is present.
Ex Crocodilus, Alligator, Gavialis
1. This group includes all extinct forms.
2. They lived from carboniferous to permen period.
3. Their skull shows one pair ot Vacuities. These vacuities are infratemporal fossal.
Ex: Dimetrodon, Cynognathus.