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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- All three organs can be withdrawn in carapace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.
They were most primitive reptiles and closest to early amphibians. They were without temporal fossae in the skull, e.g., Seymouria.
They were fish-like and had single fossa in the skull e.g. Ichthyosaurus. ’
They had diapsid skulls. Some were bipedal and gave rise to birds. A group of Archosauria also gave rise to dinosaurs, e.g., Brontosaurus.
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.
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