Based on characters Reptiles is divided into Four sub class
1. Sub-class: Anapsida:
- The skull of Reptiles are made by solid roof.
- In these Reptiles temporal vacuities are absent in the skull.
- In these Reptiles the quadrate is articulated with Otic bone.
- Limbs are strong.
- Carapace and plastron will form the body covering.
This subclass is divided into two orders.
- These Reptiles are extinct.
- They show complete cranial roof.
- Pelvic girdle is flat.
- 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.
This order includes Turtles and Tortoises.
- These are Terrestrial or aquatic.
- Body is covered by shell containing dorsal carapace and ventral plastron.
- Neck, limbs and tail are covered with scales.
- They show 4 limbs. pentadactyle are, modified into paddles in aquatic forms.
- Jaws without teeth.
- Jaws show horny sheaths.
- Quadrate is immovably articulate.
- Nasal opening is single.
- Unpaired copulatory organs are present.
- Cloacal opening is longitudinal.
- These are Oviparous.
Ex: Thonyx (Soft river terrapin), Testudo (Land tortoise). Chelone (Turtle).
2. Sub-class: Parapsida:
- This group includes extinct forms.
- Those forms lived from Triasslac period to cretaceous period.
- Their skull shows one pair of temporal vacuities. They are supratemporal fossae.
Ex: lchthyosaurus, plesiosaurus.
3. Sub-class: Diapsida:
- In these Reptiles skull shows two temporal vacuities.
- Modification of typical diapsid condition is common among these members.
This subclass is divided into two super orders Lëpidosauria and Archosauria.
Super Order: Lepldoauiia:
- These are primitive reptiles.
- 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.
- Teeth are acrodont.
- The skull shows two vacuities.
- Quadrate bone is immovable.
- An epipterygoid bone is present
- Vertebrae are Amphicoelous.
- Copulatory organs are absent in this order.
Ex: Sphenodon (Newzealand)
This includes Snakes & Lizards.
- Their body is covered by epidermal scales.
- Single supra temporaI vacuity is seen in lizards and temporal vacuity Is absent In snakes.
- Teeth are pleurodont.
- Usually procoelous vertebrae are present.
- Transverse cloacal opening is piesent.
- Male shows a pair of eversible copulatory organs, useful for copulation.
This is divided into two suborders.
Sub Order: Lacertilia:
- These are terrestrial, arboreal or burrowing forms.
- Limbs &re pentadactyl and are usually present.
- Sternum is present.
- Eyelids are movable.
- Tympanum is present.
Ex: Calotes, Chamaeleon, Draco, Varanus, Gecko.
Sub Order: Ophidia:
This sub order includes snakes.
- They are terrestrial or aquatic, or arboreal or burrowing forms.
- Temporal vacuities are absent.
- Limbs and limb girdles are absent.
- Sternum is absent.
- Eyelids are absent.
- Tympanum is absent.
- Tongue is bifid.
Ex: Python , Lycodon, Naja naja, Hydrophis, Viper.
Super Order: Archosauria:
This includes advanced reptiles.
- Teeth are on jaw margins and are set in muscular sockets.
- This super order includes a single living order Crocodilia.
- These are fresh water and predatory forms.
- Body is covered by an exoskeleton made by horny’ scales & scute.
- Teeth are thecodont.
- Quadrate is immovable.
- Vertebrae are procoelous.
- Spongy lungs are seen.
- Longitudinal cloacal opening is present.
Ex: Crocodilus, Alligator, Gavialis
4. Sub-class: Synapsida:
- This group includes all extinct forms.
- They lived from carboniferous to permen period.
- Their skull shows one pair ot Vacuities. These vacuities are infratemporal fossal.
Ex: Dimetrodon, Cynognathus.