Superorder: Archosaurs

Superorder: Archosaurs

• a group of diapsid reptiles that first evolved from Archosauriform ancestors .

• They are represented today by birds and crocodiles.

• are set apart by having socketed teeth

• four-chambered hearts

CROCODILIANS

CROCODILIANS• From the Middle Triassic

• Include the subtropical and tropical alligators, crocodiles, caimans, and a single species of gavials.

• They have survived major upheavals such as the break up of the continents and the ice ages. 

Nile crocodile - Crocodylus niloticus Caiman - Caimaninae

American alligator - Alligator mississippiensis

Gharial - Gavialis Gangeticus

Distinctive Features• powerful jaws

• protective scales

• streamlined body

• long tail

• eyes and nostrils that are positioned on top of the head

• elongated snout

Common Characteristics• They usually lay around in the water

motionless.

• Their eyes and snouts are the only part of their body that stays above the water.

• Crocodilians have sharp teeth for capturing large prey. 

• semi-aquatic predators

Common Characteristics

• They have an extra transparent eyelid on each eye that can be closed to protect their eye when underwater. 

• They have a flap of skin at the back of their throat that prevents water from seeping in when they attack prey underwater. 

• They can also close their nostrils and ears in a similar manner to prevent the unwanted influx of water.

CROCODILIANS

• Their features have changed very little from those of their prehistoric ancestors, proving that their body form has been highly successful in nature.

Crocodiles

Alligators

Gavial Caiman

Shape of snout

Slender and triangular

Broad and round

long and narrow  

slightly more pointed

protruding fourth tooth

on the lower jaw

hidden inside a socket on the upper jaw

hidden inside a socket on the upper jaw