Welcome to our presentation

“Classification of Reptiles”

Introduction The word ‘Reptilia’ came from latin word ‘Reptum’

which means ‘creep’. They have evolved from the Amphibians and in turn, give raise to the birds and mammals. As a group, the reptiles can be separated from the amphibians by their dry confined skin and from the bird by the absence of feather and from mammal by the absence of hair. From the fossil evidence it is believed that reptiles originated during the carboniferous period around 300-260 million years ago. During the Mesozoic era(Triassic to upper Cretaceous) they were the dominant vertebrates. At the end of the Cretaceous reptiles started to decline. Now most of the species are disappeared and only 4 of 16 orders survive. Only 8734 living reptiles are found all over the world. In Bangladesh 153 species of reptiles are found.

In our presentation we will classify the class Reptilia upto order according to the book of “Encyclopodia of Flora & Founa of Bangladesh” voll-25.

Characteristics of Reptalia :Predominantly terrestrial ,creeping or burrowing , mostly

carnivorous , air-breathing , cold blooded , oviparous & tetrapodal vertebrates.

Body bilaterally symmetrical and divisible into four regions – Head , Trunk , Neck & Tail.

They have two pairs of limbs , pentadectyle. Digits provided with horny claws. However limbs absnet in few lizards & all snakes.

Exoskeleton of horny epidermal scales, shields , plates and scutes .Skin dry , cornified and devoid of glands.Mouth terminal , jaws bear simple conical teeth. In turtles teeth

replaced by horny beaks. Alimentary canal terminates into a cloacal aperture.Heart usually 3-chambered , in case of crocodile it is 4-chambered.

Sinus venosus is reduced. R.B.C is oval & nucleated.Respiration by lungs throughout life.Kidneys metanephric. Excretion uricotelic.Brain with better development of cerebrum than in Amphibia. Cranial

nerves 12 pairs.Sexes are seperated. Male usually with mascular copulatory organ.Fartilization internal. Mostly oviparous. Large yolky meroblastic eggs,

covered with leathary shells, always laid on land. Development direct.Parental care usually absent.

Classification of Reptalia

Reptilia

Order: 1Testudines

Order: 2Rhynchocepha

lia

Order: 3Squamata

Order: 4Crocodylia

Order-1: Testudines This order includes turtles , tortoise & terrapins.

• They have a bony part of the shell , but some have a softy , leathery covering.

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Order-1: Testudines

• Teeth is absent. Instead each jaw is covered with a horny sheat , from a beak which is sharpened or serrated to cut flesh or plant matter.

Order-1: TestudinesThey have strong limbs to lift their heave bodies. The shape of the limb is variable. In land dwelling species the toes are turned into a solid clump; freshwater species have webbed toes & marine water species have powerful flippers.

Order-1: Testudines

•They are oviparous and lay egg in the nest chamber.

Terrapene ornata Chelydra serpentina

Order-2: RhynochophaliaThis order includes the tuataras which are restricted only in New Zealand.

•They are lizard like. A mid-dorsal row of spines are present.•Scale granular , mandibles joined by ligament.

Order-2: Rhynochophalia

•Copulatory organ is absent. Anal opening transverse.• They live on land & burrows; eats insects, molluscs or small vetebrates.

Order-2: Rhynochophalia

•They are oviparous. Lay eggs in the hole. It takes around 13 months to hatch.

Sphenodon punctatus

Order-3: SquamataThis order includes Lizards , Snakes and other extinct groups.• They have skin

with horny epidermal scales or shields . They shed their skin at intervals to emerge clear & shiny.

Order-3: Squamata• They have extra-

ordinary jointed skull and jaws that lend them both flexibility & strainght. So they can grip the larger prey more powerfully.

Order-3: Squamata•They have movable quadrate bone.

•Vomerine teeth are absent.

Order-3: Squamata•Well developed hemipenis is present.

Xantusia henshawi Rhabdophis subminiatus

Order-4: CrocodyliaThis order includes the alligators , caimans , crocodiles etc.• Body long, Head large; jaws are powerful. In head thick skin is fused with bone

Order-4: Crocodylia

• Although aquatic their limbs are well developed . Hind limbs are heavier and four fully digits , wherer the forelimbs has five digits.

Order-4: Crocodylia

They are the only ectothermic reptiles with a fully developed secondary palate and four chambered heart.

Order-4: Crocodylia

They are excellent swimmers . They swim with their limbs and legs propelling slowly or rapidly.

Order-4: Crocodylia

Distinct parental care is present. During breeding season they made mud nest to lay eggs. Female guard their nests and assist the young to escape from their eggshells and nest.

Crocodylus palustris Alligator mississippiensis