CROCODILIA.pptx

it have general characteristics of crocodilia

1. G eneral O rganisation and A ffinities of crocodilia

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

5. Distinction Of Crocodylus,Alligator and Gavialis Variation in Head shapes Alligator Crocodylus Gavialis

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.

7. Endoskeleton Skull diapsid. Quadrate immovable No parental foramen. A pseudopalate present. Ribs bicephalous .Abdominal ribs present.

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.