2. Introduction
The order crocodilia contain 25 species
which closely resemble each other.
Member of crocodilian ,appeared about 250
million year ago in early triassic period and
diversified during Mesozoic era.
All the species of alligators, caimans,
crocodiles, and gharial together are known as
“crocodilians.”
3. Distribution and Habit and Habitat
Crocodilians are found mainly in lowlands in the
tropic region .Found in south eastern ,united states .
They are aquatic animal lives in fresh water even in
sea water.
They are carnivores feed on fish, crustaceans,
molluscs ,birds and mammals.
4. External Features
Their body is long cylindrical and depressed and
head elongated into a flat snout with nostril at
the tip.
Limbs are pentadactyle,clawed and webbed.
Massive tail is laterally compressed forming a
powerful moving appendages.
Crocodilus porosus
6. Integument and Exoskeleton
Skin is thick, leathery with Horney scutes,those
on back and belly rectangular and supported by
dermal bony plates.
Tail bears dorsally a crest of broad plates,
doubled in basal half but single in distal half.
8. Digestive organ
The stomach is two chambered
one part is muscular known as Gizzard having
gastrolith.
Second part is smaller and glandular pyloric chamber.
9. Organ of Respiration
The lungs are well developed.
Lies in thorax serve by trachea.
Separated from abdominal cavity by a non
muscular
diaphragm .
10. Organ of Circulation
Completely four chambered heart.
Interventricular septum is completely divided
into right and left ventricle.
Presence of small
foramen Of panizza
11. Urinogenital system
Presence of metanepric kidney but crocodilian
do not have bladder.
Development and Reproduction
Sexes are seperated.
Males with mesian,erectile,grooved penis.
All crocodilians are oviparous.
Parental care present.
Usually 7to 95 eggs are laid depending on species.
12. Affinites
Presence of abdominal ribs.
Presence of pro-atlas.
Fusion of caudal ribs with vertebrae.
Affinite with Dinosaurs
Diapsid condition of the skull.
Uncinated process of ribs .
Dentition is thecodont .
Absence of clavical.
Affinite with Chelonian
Fixed quadrates bone.
Male have penis
Affinite with Sphenodon
13. Affinites with Lacertilia
Pro-atlas present.
Chevron bone present.
Presence of pecten.
Copulatory organ present .
Affinites with Aves and Mammales
Lungs in pleural cavities seperated by a muscular diaphragm.
Completely four chambered heart.