CROCODILIA.pptx

CROCODILIA.pptx

• 1.
  General Organisation and Affinities of crocodilia
• 2.
  Introduction The order crocodiliacontain 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 Habitand 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 bodyis 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,Alligatorand Gavialis Variation in Head shapes Alligator Crocodylus Gavialis
• 6.
  Integument and Exoskeleton Skinis 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 Noparental foramen. A pseudopalate present. Ribs bicephalous .Abdominal ribs present.
• 8.
  Digestive organ The stomachis two chambered one part is muscular known as Gizzard having gastrolith. Second part is smaller and glandular pyloric chamber.
• 9.
  Organ of Respiration Thelungs are well developed. Lies in thorax serve by trachea. Separated from abdominal cavity by a non muscular diaphragm .
• 10.
  Organ of Circulation Completelyfour chambered heart. Interventricular septum is completely divided into right and left ventricle. Presence of small foramen Of panizza
• 11.
  Urinogenital system Presence ofmetanepric 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 ofabdominal 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-atlaspresent. 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.