herpetology chapter 4 pt 4 (exam 1)

relationship among major clades

1. alligatoridae
2. crocodylidae
3. gavialidae

defining features of alligatoridae (3)

alligators and caimans

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1. teeth of lower jaw fit into pits in upper jaw (not visible)
2. inhabit areas where surface waters freeze regularity during winter
3. to breath in winter, they move their nostrils above the surface ice

defining features of crocodylidae (2)

crocodiles

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1. lower 4th tooth fits in notch in upper jaw (visible)
2. includes largest and smallest crocodylians (saltwater crocodile and west african dwarf crocodile)

defining features of gavialidae (2)

gharial and false gharial

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1. elongate, narrow snout
2. male: enlarged bulb like structure called a boss at end of snout (maybe terrestrial defense or sound communication)

body plan

1. armored
2. webbed digits
3. long flattened tail

skull (5)

1. akinetic
2. retains both temporal bars
3. skull shape different between 3 familes
4. thecodont attachment on teeth
5. secondary palate

vertebrae

procoelous

skin (2)

1. scutes and osteoderms
2. scale organs

scale organs

help to pick up vibrations from water

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on skin

aquatic adaptations

1. nictitating membrane
2. closable external ears
3. nasal disc
4. palatal valve

nictitating membrane

3rd eyelid

closeable external ears

closed when underwater

locomotion (2)

1. terrestrial
2. aquatic

the death roll

grab and spin

reproduction

1. internal fertilization (intromittent organ enters female)
2. oviparous

parental care

attentive

what is common in all taxa

1. internal fertilization
2. direct development
3. oviparous
4. temperature dependent sex determination
5. extensive parental care