Class Reptilia (Reptum = creep)

CONQUEST OF LAND

Class Reptilia

• First reptiles known from 280 million years ago, during the Permian period; – greatest radiation of reptiles in Triassic

(after the Permian) 230 million years ago, – Mesozoic era (230-70 million years ago) age

of dinosaurs;– died out in Cretaceous, about 70-80 million

years ago

• Integument:– epidermis- very thin layer;

• shed periodically

– dermis- thicker • well developed,

• has chromatophores;

• contains scales- made of keratin same material as our hair

Class Reptilia

• Cornified integument- dry scales – not homologous

to scales of fishes- bony dermal

– Keratin- same as hair and nails

– protects against dessication

Class ReptiliaFeatures that allowed them to conquer land

• Metanephritic kidney – have ureters that take urine directly to outside – able to conserve water by producing

concentrated urine– excrete uric acid instead of urea or ammonia

Class Reptilia

• Amniotic egg; – which store all food necessary for development – and prevents water loss; – are covered by leathery or calcareous shell; – laid in sheltered areas on land– Consists of 4 membranes

Class Reptilia

• Amnion -("private pond")- – inner most membrane in egg

– that forms a fluid filled sac around the fetus

• Chorion -– the outer most membrane

that surround the fetus;

– in mammals it contributes to the placenta

• Allantois -– a membrane around the

fetus

– that functions in respiration and excretion;

– also plays important role in development of placenta in mammals

• Yolk Sac - – membrane around the yolk

(i.e., the food for the fetus)

Class Reptilia

Amnion

• Reptilian jaw efficiently designed for crushing – jaws of fishes and

amphibians designed for quick closure,

– but jaws of reptiles designed for crushing prey

Class Reptilia

• Reptiles have some sort of copulatory organ permitting internal fertilization; – also associated with terrestrial existence

• Reptiles have more efficient circulatory system and higher blood pressure; – crocodilians have a four chambered heart (first seen in

vertebrates); – all other reptiles with three chambered heart – but it is more efficient in getting deoxygenated blood to

lungs; – septum in ventricle separates blood that goes to lungs

and body

Class Reptilia

• Reptiles lungs are better developed than those of amphibians- – amphibians had skin and gill respiration; – reptiles depend solely on lungs;

• All reptiles, except limbless members, have better body support than amphibians; – more efficiently designed for travel on land

Class Reptilia

• Reptilian nervous system more advanced than amphibians; – some parts of brain

(cerebrum) are enlarged;

– sense organs well developed;

– hearing is poorly developed;

– 12 pairs of cranial nerves

Class Reptilia

• Reptiles have direct development (I.e. no larval stages)– are oviparous– Ovoviviparous– some are viviparous

Class Reptilia

• Reptiles like amphibians are poikilotherms, – but some do have a degree of control of body

heat (i.e., lizard sunning self on rock)

Class Reptilia

Classification of Reptiles

Order Testudines (=Chelonia)

turtles and tortoises• 330 species• body in case of

dermal plates; • dorsal carapace and

ventral plastron; • vertebrae and ribs

fused to shell• jaws without teeth

• Suborder Sauria (lizards)– 3000 species– four limbs– moveable

eyelids and eyeswith ear openings

Order Squamatalizards and snakes

• Suborder Serpentes (snakes)– 2700 species

– limbs and ear openings absent

– no eye lids; eyes can't move

– Heat sensing pits in Pit vipers

Order Squamatalizards and snakes

Black racer

cottonmouth

Milking diamondback

• Suborder Amphisbaenia (worm lizards)– 130 species– limb girdles

vestigial– eyes hidden under

skin

Order Squamatalizards and snakes

Order Crocodilia• crocodiles and alligators

– 25 species– four chambered heart– Oviparous; 20-50 eggs

Alligator; 4th tooth bottom jawnot visible when mouth closed

Crocodile; 4th tooth bottom jaw visible when mouth is closed,jaw narrow

Order Sphenodonta =Rhynchocephalia

• tuatara– Two living species– third eye (parietal) fairly

well developed– no copulatory organs;

primitive– Only found in New Zealand– Long lived up to 70 yrs– Live in burrows