crocodiles 18-19

Archosauromorpha

• archosaurs “ruling reptiles”

• crocodilians fit in this clade

Crocodylus porosus

• largest living reptile

• the saltwater crocodile

• tropical except alligator in temperate regions

Crocodilians

• dermal scutes and osteoderms

• provide protection, thermoregulation

thecodont

• teeth in sockets

polyphyodonty

teeth take weeks to a year to replace

rocks and hard items in stomach

• for ballast

• used to grind up food because they cant masticate (chew)

crocodile biology

• high walk for longer walks → femur can be held at a range of angles

• belly crawl when plunging into water → only take prey 13ft from water edge

• dwarfed caimans feed on mammals on land

• small species can half-bound → like a gallop

eyes

• Vertical pupil for nocturnal or day vision

• Tapetum with guanine crystals creates eyeshine

bony secondary plate

separates buccal and respiratory passages

• choanae (internal nares) open behind secondary plate

• palatal valve on back of the tongue to seal off the mouth

• allows breathing while drowning prey

respiration

• alveoli

• lungs have own pleural cavity

• liver unique diaphragmatic muscle attached to the pelvins

  • pulls liver back enlarging the pleural cavities

  • sucks in air

  • aided by contraction of the intercostal muscles ( aspiration pumping)

• contracting abdominal flank muscles increases intraabdominal pressure and pushes the liver forward

• piston pump and a primitive costal aspiration pump

heart

• 4 chamber heart

• during air breathing the high pressure of the left ventricle sends high pressure oxygenated blood across the foramen of Panizza

  • goes to both systemic arches

• diving → pulmonary trunk vasoconstricts

• mixing blood ensures that the body gets all available oxygen

reproductive anatomy

• male have a single penis

• sex determination is temp dependent

Tomistoma

the false gharial

alligatoroidea - alligators and caimans

• teeth cant be seen when jaw is closed

  • teeth in lower jaw fit teeth in upper

• scales have no sensory puts

• no lingual salt glands

alligatorinae

• two species

• both live in areas where seasonal temp drop below freezing

• males typically larger

  • males 4m - famales 2.8 m

_{caiman crocodilus}

• common or spectacled caiman

• introduced to FL

paleosuchus

• dwarf caimans

• leave water to forage at night

• diets have losts of terrestrial game

crocodyloidea

• 4th tooth of lower jaw → notch in upper jaw

• sensory pits in scales

• salt glands on tongue

  • wide distrib

Gavialidae (gavialis)

• elongate narrow snouts

• narrowest jaws among crocs

• Piscivorous

• boss or ghara (pot)

Crocodylidae

• 1st mandibular tooth often penetrates premax

• some relatively broad → snouted others rather slender

C. Johnsoni

• half- bounds

C. Porosus

• saltwater

• largest living reptiles → 7m 2,000 lbs

• tidal and freshwater

• rivers and lakes

• far out to sea

C. niloticus

• Nile crocodile

• C. suchus

• mummies

• kills 300-400 people per year

Crocodylus acutus

• American crocodile

• hump in front of eye

• coastal habitats around rivers and lakes