Geographical distribution: Found in South Eastern Australia and Tasmania. Triassic to Recent.
Habit and habitat: It is a native of rivers, pools and creeks. It burrows to 12 to 15 meters along the river banks. It feeds on fresh-water invertebrates, carried in cheek pouches.
Comments:
1. Commonly called Duck-billed-Platypus.
2. It measures about 50 cm in length having fine short fur, dark brown colour and combines the characters of a duck with a mammal.
3. Body is divided into head, thick trunk and tail. Body and tail contain soft hairs.
4. Head distinct. Upper jaw produced to form a flattened beak which is covered with a smooth. hairless skin that forms a free fold at the base of the beak. Head contains the nostril mouth and external ear opening.
5. Adults have no teeth. Jaws covered with horny plates. Pinnae absent.
6. Forelimbs and hind limbs have 5 digits, web and clawed toes. Hind limb has
horny spur. Tail is flattened and adapted for swimming.
7. Coracoid and precoracoid present. T-shaped interclavicle.
8. Eyes small having a nictitating membrane. Mammary glands without nipples.
9. Cloaca present. Ureters open in the dorsal wall of urinogenital passage. Testes abdominal, penis conducts only sperms. Oviducts distinct, uterus or vagina absent.
10. Female makes a nest of roots and leaves during spring in burrows, and lays 1-3 eggs. About 0.5 cm long, the young one is hatched. It nurses by lapping up milk secreted by scattered mammary glands on the abdomen of the female.
Special features: Ornithorhynchus is an egg-laying mammal ard exhibits reptilian, mammalian and intermediate characters. Reptilian features are urinogenital system, precoracoids, absence of pinna and corpus collosum. Mammalian features include hair, diaphragm, 4-chambered heart. 3- ear ossicles, etc. Intermediate features include mammary glands without nipples, acromion spines in the scapulae and body temperature between 25 - 28?C is an imperfect thermoregulator.
Source:
1. Practical Zoology Vertebrates by S.S.Lal. 2. A Manual of Practical Zoology Chordates by Dr. P.S. Verma.
