Ch. 17--Crocodilians (Nov. 28) (copy)

Crocodylians

• Largest living species of reptiles

• Important predators of tropical and subtropical

  • 3 of 26 living species occur in temperate envts

Systematics of Crocodylians

• Alligatoridae

  • Curved flatelong snout

  • Alligators and Calmans

• Crocodylidae

  • Flat pointed snout

  • Crocodiles

• Gavialidae

  • Thin long pointed snout

  • Gharial and false gharial

Characters of Crocodylians

• Dorsal nostrils allow breathing by floating at surface of water

• Laterally-flattened tail helps propel efficiently through water

  • Legs held close to body to reduce drag

Early Crocodylians

• Evolved in late Triassic

• Originally terrestrial predators

  • Long limbs, small body sizes

  • Possibly bipedal

• Derived species (and living taxa) mostly aquatic

  • Small limbs, large body sizes

  • Some extinct species exhibited gigantism

Foraging Strategies

• Hunt in ambush in water

• Catch prey on land by ambush or short bursts of running

• Gather to collect fish

• Use sticks as lures to capture wading birds

Communication

• Both sexes vocalize, especially in courtship and aggressive interactions

• Males produces long distance subsonic vibrations

• Aggregate during courtship

Parental Care 1

• Complex and probably universal

  • Defend offspring in creches for 2-3 years

• Construct nest and attend to its care

  • All have Type 11 TSD, but large nests usually have wide range og temps

• Respond to calls of hatchlings

• Probably synapomorphic for archosaurs

  • In extinct pterosaurs and dinosaurs to