Crocodylians
Herpetoculture
Pensacola Jr College
Fossil history
w Crocodylians are archosaurs
• Related to birds and
dinosaurs
w Early crocodylians bipedal
and less aquatic
Diapsida
Classification
w Phylum Chordata
w Subphylum Vertebrata
w Superclass Tetrapoda
w Class Reptilia
w Order Crocodylia
Order Crocodylia
w Range: N and S America, Africa,
Asia, Australia
w Body:
• Elongated lizard-like body
• Long snout
• Long laterally compressed
tail
• Short limbs (rear somewhat
larger) with webbed feet
• Unique reptilian walk
Range Map
High Walk
Order Crocodylia
w Skin:
• Heavy armor due to plates of
bone (osteoderms) within dorsal skin
• Some have ventral osteoderms
• Heavy epidermal scales
Armor
Order Crocodylia
w Sensory:
• Clear nictitating membrane
drawn across eye in water
• Eyes and nostrils placed on
top of head, nostrils valved
• Scutes have conspicuous pits
with osmosensory function
• Salt glands on tongue
Skin pit receptors
Order Crocodylia
w Mouth:
• Well developed secondary
palate
• Internal nares can be closed
off from throat by fleshy folds
w Breathing:
• Diaphragm – like structure
• Well-developed alveoli
Nares and palate
Palatal Valve
Order Crocodylia
w Heart:
• 4 chambered heart
• Normally some mixing of
blood to posterior body
• During diving, high left
ventricle pressure causes blood shunt through Foramen of Panizzae à all blood to body is oxygenated
Order Crocodylia
w Reproduction:
• Oviparous
• Mound nests or exposed eggs
• 25 to 60 eggs with 1 – 3
month incubation period
• Single penis in males
• Parental care by female
• All have TDSD
Order Crocodylia
w All are aquatic or
semi-aquatic
w Live mainly in tropics or
subtropics
w Carnivores – nocturnal
hunters, grasp prey with sharp teeth and thrash to dismember
Order Crocodylia
w Use sound as major
communication form:
• Vocal cords above water
• Rapid contractions of body
wall musculature underwater
• Roars, grunts, coughs, purrs
• Young in eggs use sound to
synchronize hatching
Classification
w Class Reptilia
w Order Crocodylia
• Family Alligatoridae
• Family Crocodylidae
• Family Gavialidae
Family
Alligatoridae =
alligators and caimans
8 species
Family Alligatoridae
w Range: southern N America, S
America, Yangtze River in China
w Physical characteristics:
• Adult size = 6.5 to 18 feet
• Short broad snout
• No lower teeth visible when
mouth closed (fit in upper jaw)
Family
Alligatoridae
w Habitat: large rivers, lakes,
swamps, lagoons
• American alligator freely
enters coastal marine waters
w Feeding: mammals, birds,
amphibians, reptiles, slow moving fish
American Alligator
Chinese Alligator
Spectacled Caiman
Black Caiman
Family
Crocodylidae =
crocodiles, muggers, and false gharial
14 species
Family
Crocodylidae
w Range: Central America,
northern S America, Africa, SE Asia, Australia
w Physical characteristics:
• Adult size = 5 to 26 feet
• Short / broad or long /
slender snout, depending on lifestyle
• 4th mandibular
tooth visible when mouth is closed
Family
Crocodylidae
w Habitat: varied by species,
fw or sw
w Feeding: some specialized on
fish, others generalist feeders
w DANGER
• Saltwater crocodile and Nile
crocodile are main species that have eaten humans
American Crocodile
Slender-snouted
crocodile
Australian
freshwater crocodile
Saltwater
Crocodile
Nile crocodile
Mugger
False Gharial
Family Gavialidae
=
gharial
1 species
Family Gavialidae
w Range: Northern India
w Physical characteristics:
• Adult size = 10 to 18 feet
• Males larger and have ghara
• Elongated narrow snout
• Relatively weak limbs, most
aquatic crocodylian
Family Gavialidae
w Habitat: fast-flowing rivers
w Feeding: primarily fish
w Nesting: holes in sandbanks along the rivers
Gharial
Husbandry Info