Crocodylians
-diapsid skulls
Oviparous; internal fertilization
Semi-aquatic; bask on shorelines
-12-60 eggs per clutch
nest in mounds of vegetation mostly
adapted well to an aquatic niche
Proposed
Crocodylian Phylogenies
Newest crocodylian phylogeny – Roos et al. (2007)
Molecular Phylogenetics and Evolution 45: 663–673
Character
Family Alligatoridae
Family Crocodilidae
Family Gavialidae
Popular Name
Alligators and Caimans
True crocodiles
Gharial
Head & Snout
More oval than triangular
Broad, triangular head with a short Snout
Beak-like extension of the
snout
4th lower tooth (when the mouth is closed)
Not visible from outside
Visible from outside
Visible from outside
Mandibular Symphysis (joint between two
halves of lower jaw)
Extends to a level less
than 23rd tooth
Extends to a level less than23rd tooth
Extends to a level of 23rd
or 24th tooth
Distribution
S. America, China, USA
Asia, Africa, Australia & Pacific Islands & USA
Asia (India & Nepal)
No. of Genera (No. of species given in
brackets)
Alligator(2)
Caiman(2)
Paleosuchus(1)
Melanosuchus(2)
Crocodylus (11) Osteolaemus(1) Tomistoma(1)
Gaviali
Family Gavialidae
Gharials
monotypic
Gavialis gangeticus
-SW Asian River Basins
longest and narrowest jaws of all
crocodylians
-males grow a boss on snout tip
-most aquatic of crocodylians
-impale fish by swiftly moving head
-4 m in length
(not really dangerous to man)
Family Alligatoridae
Subfamily Alligatorinae
2 species
Alligator mississippiensis
American Alligator
SE USA
4 meters
opportunistic carnivore
breed at 2.1 meters in length
young have a very different coloration
AR Post National Memorial
females show parental care
A. sinensis
Chinese Alligator
2.1 meters
40% of diet is mollusks
hibernates
similar reproduction to American
lower jaw fits within mouth upon closure
Subfamily Caimaninae
3 genera; 7 species
-Central to south America, Amazonia
-small to large 1.7m to 5m
-freshwater
-mound nest builders
-harvested and habitat destruction
Caiman crocodilus
introduced into south FL.
interaction with FL crocs?
Dwarf Caiman (Paleosuchus)
Family Crocodylidae
Crocodiles and False Gharials
2 subfamilies
pan - tropical
moderately long and broad jaws
when mouth is shut,
fourth mandibular tooth is exterior
Subfamily Crocodylinae
2 genera; 14 species
Crocodylus acutus
-American crocodile
-up to 15 ft.
-habitat destruction, moving into salt water
-400 left in Everglades
C. porosus
-Estuarine crocodile
-up to 20 feet
-often seen at sea
-opportunistic predator
C. niloticus
-Nile Crocodile
-16 feet
-quite dangerous, heavily populated Nile Valley
-perhaps 5,000 people a year could be eaten
-can build a sand nest but prefers mounds
Osteolaemus
Dwarf crocodile
exclusively nocturnal
Subfamily Tomistominae
False Gharial
monotypic
Tomistoma schlegelii
-Borneo and Sumatra, Malay Peninsula
-fish eater like gharial, can also ambush
poorly known, overhunted, habitat destruction