Chapter   13 - ARCHOSAURS

Taxa---crocodiles, dinosaurs, birds

Order Crocodylia (Triassic - Recent)

alligators and caimans; crocodiles; gavials

Caiman crocodilus; Common caiman in Costa Rica, photograph by Ben Hernandez, © 2001, used with permission

Characteristics

  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
  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
    1. alligators and caimans
      e.g., American alligator Alligator mississippiensis. photographs © 2001by Dr. Allan H. Chaney,  used  with permission
    2. mostly New World plus Chinese alligator
    3. freshwater
    4. broad snouted forms with varied diets
    5. lower teeth tend to fit inside uppers
    6. 4th lower tooth not visible when mouth is closed
    7. median septum between nares

     

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



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

    1. Gavialidae
      1. a single species, the gharial (Gavialis gangeticus)
      2. India and Burma
      3. up to 8 m long
      4. 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

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

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


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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