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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 Class Reptilia • 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 Features that allowed them to conquer land • Cornified integument- dry scales – not homologous to scales of fishes- bony dermal – Keratin- same as hair and nails – protects against dessication Class Reptilia • 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")– – • Chorion – – • the outer most membrane that surround the fetus; in mammals it contributes to the placenta Allantois – – – • inner most membrane in egg that forms a fluid filled sac around the fetus 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) Amnion Class Reptilia • 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) 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 Order Squamata lizards and snakes • Suborder Sauria (lizards) – 3000 species – four limbs – moveable eyelids and eyes with ear openings Order Squamata lizards and snakes cottonmouth • Suborder Serpentes (snakes) – 2700 species – limbs and ear openings absent – no eye lids; eyes can't move – Heat sensing pits in Pit vipers Black racer Milking diamondback Order Squamata lizards and snakes • Suborder Amphisbaenia (worm lizards) – 130 species – limb girdles vestigial – eyes hidden under skin Order Crocodilia • crocodiles and alligators – 25 species – four chambered heart – Oviparous; 20-50 eggs Alligator; 4th tooth bottom jaw not 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