• First true land dwellersFirst true land dwellers

• Lay eggs on land- internal fertilizationLay eggs on land- internal fertilization– Amniotic egg covered with shell to protect Amniotic egg covered with shell to protect

from drying out (“land egg”)- rubberyfrom drying out (“land egg”)- rubbery– Have four embryonic membranes- amnion, Have four embryonic membranes- amnion,

yolk sac, allantois, corionyolk sac, allantois, corion

• Thick skin with keratin (waterproof and hard)- Thick skin with keratin (waterproof and hard)- covered with scales or platescovered with scales or plates

• Cold blooded (poikilothermic)Cold blooded (poikilothermic)

• First fossils- 310 myaFirst fossils- 310 mya

– Mesozoic era- 225 mya to 65 mya- age of Mesozoic era- 225 mya to 65 mya- age of reptilereptile

– Jurassic and Cretaceous periods- many Jurassic and Cretaceous periods- many different types (swim, land, flew)- different types (swim, land, flew)- herbivores, herbivores, omnivores, and carnivoresomnivores, and carnivores

• Strong bony skeleton Strong bony skeleton and well developed and well developed lungs (2 lungs except lungs (2 lungs except snakes with 1)snakes with 1)

• Most have 4 limbs Most have 4 limbs (snakes have vestigial (snakes have vestigial feet on pelvic bone feet on pelvic bone called claspers)called claspers)– More vertical under More vertical under

trunk than trunk than amphibiansamphibians

– Limbs larger, Limbs larger, stronger, and more stronger, and more support more weight support more weight than amphibiansthan amphibians

• Claws on toes to dig Claws on toes to dig and climband climb

• Small brain but Small brain but complex behavior complex behavior (i.e. rituals, maternal (i.e. rituals, maternal instinct)instinct)

• Excretory system Excretory system minimizes water loss minimizes water loss (metanephric (metanephric kidneys)kidneys)

• Three chambered Three chambered heart (except heart (except crocodilia with four)crocodilia with four)

• Modern dinosaur (?)Modern dinosaur (?)

• About 60 cm. longAbout 60 cm. long

• Only cool living reptile Only cool living reptile (50 deg.)- lives in New (50 deg.)- lives in New ZealandZealand

• Primitive body structure Primitive body structure (very different from (very different from lizards)lizards)

• Third eye on top of headThird eye on top of head– Parietal eye- light sensitive surface but no muscles- Parietal eye- light sensitive surface but no muscles-

possibly used for temperature controlpossibly used for temperature control

• Double row of teeth on top (bottom row fits in Double row of teeth on top (bottom row fits in between)between)

• No copulatory organ in malesNo copulatory organ in males

• Extremely slow reproductive rateExtremely slow reproductive rate

– Egg formation takes four yearsEgg formation takes four years

– Eggs hatch in 12 monthsEggs hatch in 12 months

• EndangeredEndangered

• Land an waterLand an water

• Up to 5’ and 560 lbs.Up to 5’ and 560 lbs.

• Can live over 150 yearsCan live over 150 years

• Plates (scutes) make up Plates (scutes) make up shell- 3 partsshell- 3 parts– Carapace (top), plastron Carapace (top), plastron

(bottom) and hinge or (bottom) and hinge or bridgebridge

– Some can pull head and Some can pull head and limbs in shelllimbs in shell

– Cannot leave shell- Cannot leave shell- vertebrae attachedvertebrae attached

• No teeth- use jaws No teeth- use jaws and claws to tear and claws to tear food (some have food (some have one egg tooth)one egg tooth)

• Hard shelled turtles Hard shelled turtles more docile- softer more docile- softer shells more shells more aggressive (i.e. aggressive (i.e. snappers)snappers)

• Well known for digestive problemsWell known for digestive problems

• Many dwindling due to human interactionMany dwindling due to human interaction

• Most advanced reptilesMost advanced reptiles

• Active water dwellers- carnivoresActive water dwellers- carnivores

– Spin to drown preySpin to drown prey

– Chunk feeders- hide carcass to rotChunk feeders- hide carcass to rot

• Eyes and nostrils above head (can stay Eyes and nostrils above head (can stay submerged and still breathe)submerged and still breathe)

• Valve over nose allows mouth open under Valve over nose allows mouth open under waterwater

• Lie in wait for preyLie in wait for prey

– Alligators much less aggressiveAlligators much less aggressive

• Tail propels through waterTail propels through water

• Webbed clawed feet help climb over Webbed clawed feet help climb over mudmud

• Few muscles to open mouth- many to Few muscles to open mouth- many to closeclose

Alligator- broad head, round snout- teeth fit inside upper jawCrocodile- triangular head, pointed snout- two protruding teeth

• Lizards have legs, claws, external ears and movable eyelids (snakes do not)

• Some evolved into highly specialized Some evolved into highly specialized formsforms

• Use tongue to “smell” airUse tongue to “smell” air– Jacobson organ to do thisJacobson organ to do this