Reptilia General Characteristics, Classification and Examples | Free Biology Notes

Reptilia General Characteristics, Classification and Examples

After reading this article you will learn about Reptilia General Characteristics, Classification and Examples

Reptilia General Characteristics

  • They are basically terrestrial but some are aquatic
  • Body is divided into 4 parts:- Head, neck, trunk and tail
  • They are cold blooded animals or poikilotherm
  • Limbs two pairs, five clawed digits in each limb (Some limbless)
  • Skin dry, rough and non glandular. Endoskeleton is made up of epidermal scales or plates
  • Alimentary canal terminates into cloaca
  • Respiration only by lungs
  • Heart is usually 3 chambered or partially four chambered (4 Chambered in crocodile)
  • Brain developed, cranial nerves 12 pairs
  • Ear in the form of tympanum
  • Jacobson’s organ present in the roof of buccal cavity concerned with smell
  • They are unisexual, oviparous, internal fertilisation.
  • Development is direct. No metamorphosis and parental care found

Classification of Reptilia

The class Reptilia is differentiated into two major sub-classes: Anapsida and Diapsida

Subclass 1. Anapsida

  • The dermal bones form a complete roof over the skull with no temporal fossae.
  • These are sub-divided into Cotylosauria and Chelonia.
  • Modern chelonians are classified according to the method of retracting the head in the shell.
  • Turtles, tortoises, and terrapins belong to this group.
  • These are include only one order – Chelonia

Order – Chelonia

  • Terrestrial, marine and fresh water animals
  • Body covered in two shell plates:- Dorsal shell – carapace and Ventral shell – Plastron
  • Limbs clawed, webbed and paddle like
  • Jaws horny beak like and no teeth
  • All three organs can be withdrawn in carapace
  • Cloacal aperture helps in respiration (Cloacal respiration)
  • E.g., Che lone (turtle), Testudo (Tortoise), Trionyx (Terrapin)

Subclass 2. Diapsida

  • There are two temporal vacuities in the skull.
  • They are diverse of all reptiles.
  • The dinosaurs and pterosaurs are included in this group.
  • These are divided into three orders – Rhynchocephalia, Squamata and Crocodilia

Order 1. Rhynchocephalia

  • Most of the species of this order are found in form of fossils
  • Only sphenodon punctatum species is live (found in new Zealand only)

Order 2. Squamata

Squamata It includes two suborders:- Lacertilia and Ophidia

Suborder (1) Lacertilia

  • Limbs will developed
  • Eyelids movable
  • Nictitating membrane found in eye
  • Tympanum present
  • E.g., Lizards, such as Chameleon (Tree lizard), Calotes (Garden lizard), Hemidactylus (wall lizard)

Suborder (2) Ophidia

  • Limbs are absent
  • Eye lids immovable
  • Nictitating membrane absent
  • Tympanum absent
  • E.g., snakes, such as Naja (Cobra), Bungarus (Krait), Vipera (Viper).

Order 3. Crocodilia

  • Freshwater animals found on land and water
  • 4 chambered heart present
  • Largest modern reptiles
  • Skin is covered by bony plates
  • Snout long
  • E. g., Crocodilus (Crocodile), Alligator, Gavialis (“Gharial”).

Extinct Groups of Class Reptilia:

Following extinct groups of class reptilia are important to mention here.

i. Cotylosauria:
They were most primitive reptiles and closest to early amphibians. They were without temporal fossae in the skull, e.g., Seymouria.

ii. Ichthyopterygia:
They were fish-like and had single fossa in the skull e.g. Ichthyosaurus. ’

iii. Archosauria:
They had diapsid skulls. Some were bipedal and gave rise to birds. A group of Archosauria also gave rise to dinosaurs, e.g., Brontosaurus.

iv. Synaptosauria:
The skull had a single temporal fossa on either side. They were mammal-like reptiles that later on gave rise to mammals, e.g. Plesiosaurus.

For more detailed information about Animal Kingdom, visit YouTube Channel.

1 thought on “Reptilia General Characteristics, Classification and Examples | Free Biology Notes”

Leave a Comment