Amniotes

Eggs with 4 membranes Have dry, tough or scaly skin 2 kidneys Groups

Synapsids – all mammals Sauropsids – reptiles and birds

27 Jan. 2010 Reptiles.ppt 2

Amniote egg

Embryo develops membranes within shell amnion, chorion, yolk

sac, allantois Shell permeable to air

(breathes) Amnion, chorion

retain water to keep embryo wet.

Reptiles

No longer a formal taxon, not monophyletic Refer to lineages that show basic amniote features,

but not derived traits of birds/mammals Chase prey Well-muscled jaws 4 limbs good at supporting weight Lungs Bigger brains

General Characteristics

Live in a variety of land and water habitats Cold-blooded Both sexes have cloaca – functions in excretion and

reproduction adaptations to terrestrial environment

Keratinized skin - epidermal scales- reduce water loss abrasion resistant

Internal fertilization- Sperm deposited in female body

Groups

Crocodilia (crocodiles, gavials, caimans, and alligators)

Sphenodontia (tuataras from New Zealand)

Squamata (lizards, snakes, and worm lizards):

Testudines (turtles and tortoises):

Turtles

Bony or cartlingous shell attached to skelton

Horny plates act as teeth

Vunerable because of predators, hunting, nesting site destruction

Lizards

Largest order Skin has horny scales or

sheilds

Snakes Limbless, can have

vestigial structure Snakes can open jaw to

accomodate large prey May use venom to

subdue prey Lack eyelids, external

ears Females store sperm

and lay several clutches

Tuataras

Two species surviving in New Zealand

Resemble amphibians in brain and locomotion

Have 3rd eye under skin May detect

daylentgh and light intensity

Crocodilians

All are predators in/near water Powerful jaw, long snout, sharp teeth Only ones with a 4 chambered heart like birds and

mammals Engage in parental behavior Closest relatives to birds