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 ( million years ago) age of dinosaurs; –died out in Cretaceous, about 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 Reptilia Features 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 eyes with ear openings Order Squamata lizards 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 Squamata lizards and snakes Black racer cottonmouth Milking diamondback

Suborder Amphisbaenia (worm lizards) –130 species –limb girdles vestigial –eyes hidden under skin Order Squamata lizards and snakes

Order Crocodilia crocodiles and alligators –25 species –four chambered heart –Oviparous; eggs Alligator; 4 th tooth bottom jaw not visible when mouth closed Crocodile; 4 th 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