Reptiles are the first land animal vertebrates belongs to animal kingdom.
Characteristics Features of Reptilia
- Class Reptilia (L. Reptilia = creeping) includes animals that are cold-blooded (poikilothermal) and terrestrial or aquatic tetra-pods.
- The body is covered with body epidermal scales or scutes.
- The skin is dry and glands are absent.
- Limbs are tetrapodous and pentadactyl, provided with claws.
- Skull with single medial occipital condyle, and T-shaped interclavial present.
- Mandible consists of many pieces and articulates with cranium through the quadrate bone.
- Vertebrae are gastrocentrous.
- Ribs form a true sternum.
- Respiration is done via lungs only.
- The heart is three-chambered and incompletely divided ventricle is present.
- Right and left aortic arches are complete and functional.
- Kidneys are metanephric. Nephrostomes are absent. Each kidney has a separate ureter.
- Twelve pairs of the cranial nerve are present.
- The lateral sense organs are absent.
- The develpoment includes the formation of amnion, chorion, allantois and yolk sac.
- Fertilization is external, eggs are laid on land. They are oviparous.
- The cloaca is present.
- Examples of Reptilia: Terrapin, Wall Lizard, Garden Lizard, Indian Cobra, Crocodile etc.
Classification of Reptilia
Subclass 1: Anapsida
- Solid roof of the skull.
- No temporal fossae in the skull.
Order 1: Chelonia
- Terrestrial or aquatic.
- Tetrapoda, limbs are modified as paddles.
- The body is enclosed in a body shell of dorsal carapace or ventral plastron.
- Tail, head, neck are retractable into shell.
- Jaws without teeth but with horny sheaths.
- Quadrate bone is fixed.
- Vertebrae and ribs are fused with carapace.
- Pubis and ischia forming symphysis.
- Male with single copulatory organ.
- Examples: Chelone, Kachuga, Trionyx
Subclass 2: Parapsida
- Single temporal vacuities are present behind the eye bounded below by post-frontal and supra temporal bones (extinct form).
Subclass 3: Diapsida
- Two temporal vacuities on each side of the skull.
- Post-orbital and squamosal usually meet between the temporal vacuities.
Order 1: Rhynchocephalia
- Teeth acrodont.
- Epipterygoid bone is present.
- Qudrate bone is immovable.
- Parietal foramen and pineal eye are present.
- Vertebrae are amphicoelous.
- Abdominal ribs are present.
- Example: Sphenodon
Order 2: Squamata
- Body covered by epidermal scales.
- Single temporal vacuity in lizard and no temporal vacuity in snakes.
- Teeth pleurodont.
- Cloacal opening is transverse.
- A paired copulatory organ is present in males called hemipenis.
- Limbs may be present or absent.
Suborder 1: Lacertilla
- Terrestrial, arboreal and burrowing animals.
- Single temporal vacuity is present.
- Limbs pentadactyl and clawed.
- The ramus of mandible are fused in front.
- Eyelids movable.
- Sternum is present.
- Examples: Draco, Varanus, Calotes, Uromastix, Hemidactylus, Ophiosaurus
Suborder 2: Ophidia
- Terrestrial, aquatic or burrowing animals.
- Temporal vacuities are absent.
- Limbs, Sternum and Tympanum are absent.
- The ramus of the mandible are united by ligament.
- Eyelids are immovable.
- Tongue is bifid and protrusible.
- Zygosphene and zygantra are present in vertebrae.
- Poison glands and fangs may be present or absent.
- Examples: Cobra, Viper, Python, Krait.
Order 1: Crocodile
- Fresh water and predaceous.
- The body is covered by epidermal horny scales and scutes.
- The tail is long and laterally compresses.
- Maxilla, palatine and pterygoid are united to form a secondary palate.
- The thecodont teeth are present.
- Quadrate bone is immovable.
- Both supra and infra temporal arches present.
- Procoelous vertebrae are present.
- Sternum is present.
- Cervical vertaebrae with two headed ribs.
- Thoracic ribs with ancinate process.
- Abdominal ribs present.
- Prepubis present. Pubis does not take part in the formation of acetabulum.
- The heart is perfectly four chambered, interventricular septum is present.
- Cloacal opening is longitudinal.
- Male has a median unpaired penis.
- Examples: Crocodilus, Alligator, Gavialis
Subclass 4: Synapsida
One temporal vacuity is present on each side surrounded by post-orbital and quadratojugal (extinct form).
Some Examples of Reptilia
Classification of Trionyx
It is widely distributed in India, North America, Asia, Africa and Malaysia.
Habit and Habitat
- Aquatic, found in fresh water ponds and rivers. It is a voracious feeder. Trionyx gangeticus is very common in India.
- Carnivorous, feeds upon mollusk, fishes and frogs.
Characteristics of Trionyx
- It is commonly known as soft river terrapin.
- The body is flat, oval and enclosed in a body shell comprising dorsal carapace and ventral plastron.
- The shell has no horny scales but a covering of soft leathery skin.
- The color is olive green above, yellowish below.
- The head is triangular having a pointed snout.
- Jaws are provided with horny sheath., teeth are absent.
- Limbs are modified as paddles for swimming.
- Head, neck, limbs and tail are retractile into the shell.
- Oviparous, eggs are laid outside water in moist soil.
Classification of Hemidactylus
World wide distribution and found mainly in India, Sri Lanka, China, Europe, Asia and America.
Habit and Habitat
- Its is commonly known as House Lizard,
- It is nocturnal, fast runner and insectivorous, feeds mainly on insects.
Characteristics of Hemidactylus
- It is commonly known as wall lizard or house lizard.
- It measures about 18 cm. in length and is pale green in color.
- Body is divisible into head, trunk and tail.
- Head is broad and flat, eyelids are fused over eyes.
- Ear openings vertical. Tongue is short, sticky, slightly notched and protrusible.
- Digits are clawed and dilated with two rows of lamellae on the other surface for the movement of ceilings and smooth surfaces.
- Tail is moderately long and can break off as an unossified part of the caudal vertebrae. Tail is regenerated again, and this phenomenon is known as autonomy.
- Oviparous. Lives in crevices of walls.
- Male with femoral pores on the thigh.
Classification of Calotes
It is mainly found in India, China and Malaysia.
Habit and Habitat
- This lizard is found among hedges, shrubs etc.
- Diurnal and insectivorous, feeds on insects, spiders etc.
Characteristics of Calotes
- Calotes is commonly known as Garden lizard.
- It may reach a length of 35 cm.
- The body is divisible into head, neck and tail.
- The body is covered by imbricate epidermal scales.
- A crest of spine is present on dorsal side of neck and back.
- Mouth is anteriorly placed on the head. The cloacal opening is transverse.
- The tail is extremely long and cylindrical and does not break.
- Gular sacs are absent, but male develops a single pouch during breeding season.
- It has a remarkable power of changing body colors. It changes its body color from olive green to yellow and red during courtship.
- The animal is oviparous.
Classification of Naja
It has a very wide distribution, found in Africa, China, Philippines, Tasmania, Australia, New Guinea, Egypt and India.
Habit and Habitat
- Diurnal, lives in holes, under stones and in thick vegetation.
- Carnivorous, feeds on frogs, rats, lizard and other snakes.
Characteristics of Naja
- Naja is commonly known as Indian Cobra or Nag.
- The body is elongated and grows up to two meters in length.
- The body is also divisible into head, neck and tail,
- The color of the body is brown or black.
- The hood is spread out by expansion of skin and foldable ribs of the neck region. A spectacle mark is present on the hood.
- Eyes are small with round pupils, nostrils are present.
- Tongue is bifid, protrusible and thermo-sensory.
- Third supralabial is large and touches the eye and nostril.
- Poison glands are present. Poison is deadly.
- Fangs are large, anterior, grooved and permanently erect.
- Tail is cylindrical and tapers posteriorly.
- Produces large hissing sound when provoked.
- The death of the person bitten is due to respiratory failure. Poison contain neurotoxins.
Classification of Crocodilus
It is chiefly found in tropical regions including India, Africa and Central America.
Habit and Habitat
- Found in fresh water, rivers and lakes, makes long tunnels below the level of water.
- Carnivorous, feeds on fishes and mammals, dangerous to man.
Characteristics of Crocodilus
- Commonly known as crocodile or Magar in Hindi (Language spoken in India.) .
- The body is divisible into head, neck and tail and measure up to 5 meters in length.
- The body is covered by thick epidermal scutes or scales and the tail is laterally compressed into a powerful organ of swimming.
- Head is triangular with anteriorly produced snout, which is broad and pointed. Nostrils present on the tip of the snout are valvular.
- Limbs are pentadactyl with five fingers and four toes.
- The fingers are webbed to be used in swimming.
- Teeth are powerful and are arranged in rows. The fourth mandibular tooth is the largest and fits in a notch.
- Ears are covered by a flap of skin.
- Heart is four-chambered with two auricles and two ventricles.
- It is an oviparous animal.
- It lives in a tunnel under water and occasionally attacks man.