Chapter   13 - ARCHOSAURS

• Infraclass ARCHOSAUROMORPHA

  Characteristics [fig 14-4]

  1. antorbital fenestra mandibular fenestra
  2. fourth trochanter on femur [trend toward bipedalism]
  3. flattened (instead of rounded ) teeth set in sockets
  4. orbit shaped like an inverted triangle

Taxa---crocodiles, dinosaurs, birds

1. massive buttressed skull with sculptured dermal bone
2. antorbital fenestra small to closed
3. posterior region of skull pneumatic
4. secondary palate extends to pterygoids; a flap of tissue at base of tongue forms a seal so crocodiles can breath with only the nostrils exposed
5. nostrils terminal
6. well-developed limbs (inheritance from Triassic terrestrial ancestors), can gallop; limbs are tucked ventrally
7. FOUR chambered heart with a septum completely dividing the ventricles
   • intercardiac shunt to shift blood from pulmonary artery to aortic arch to skin when basking or diving
8. oviparous
9. temperature dependent sex--low nest temperature produces females (unlike turtles)
10. Extensive parental care of eggs and young by male and female. [fig 14-7]
11. 21 living species
12. mainly tropical to subtropical
13. modern forms are semiaquatic

Taxa

1. Deinosuchus from the late Cretaceous had a skull 2 m long, a body 8-10; mass 2000-5000 kg;  3x-5x larger than largest recent crocodilian
2. crocodiles, alligators, and gharials
   1. alligator vs. crocodile from Crocodilian Biology Database 
   1. North Carolina State Aquarium
   2. Texas Memorial Museum
   3. Crocodilian biology database
   4. Species accounts
      

   Alligatoridae alligators and caimans e.g., American alligator Alligator mississippiensis. photographs © 2001by Dr. Allan H. Chaney,  used  with permission mostly New World plus Chinese alligator freshwater broad snouted forms with varied diets lower teeth tend to fit inside uppers 4th lower tooth not visible when mouth is closed median septum between nares

3. Crocodylidae widely distributed rivers and estuaries and ocean American crocodile Crocodilus acutus Estuarine crocodile (India to Australia) C. porosus up to 7 meters, 1000 kg variable snout width, widest snouts have the most varied diets (turtles, fishes, terrestrial animals) narrow snouts eat fish teeth alternate--intermesh 4th tooth visible when mouth is closed no median septum between nares

   Crocodylus acutus, American Crocodile; Gerald and Buff Corsi,  California Academy of Sciences © 2001 California Academy of Sciences

4. Gavialidae a single species, the gharial (Gavialis gangeticus) India and Burma up to 8 m long mandible with a long symphysis a very narrow snout, for catching fishes

   Gavialis gangenticus; Gerald and Buff Corsi,  California Academy of Sciences © 2001 California Academy of Sciences

   
   

Order Pterosauria

• flying archosaurs [fig 14-8]
• elongate metacarpal IV and digit IV

Ramphorhynchoidea (U. Triassic. - U. Jurassic.)

• long tails and long fifth toes

Pterodactyloidea (U. Jurassic. - U. Cretaceous.)

• short tails and short fifth toes; long wing metacarpal;
• includes Pteranodon  5-8 m wingspan and  Quetzelcoatlus wing span of 11-12 m., weight of approximately 65 kg

DINOSAURIA [fig 14-10]

Ornithischia [fig 14-13]

1. Ankylosauria
2. Stegosauria
3. Ceratopsia
4. Ornithopoda [fig 14-14]

Saurischia

Sauropoda [fig 14-17]

Theropoda [fig 14-18]

Carnosauria

Coelurosauria

Maniraptora

dromaeosaurs: Deinonychus [fig 14-19, 14-20]

Archaeopteryx [fig 15-1,2,3,4]

Aves

Dinosaur eggs and nests [Box 14-1, Fig. 14-15]

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