Classification of Ornithorhynchus (Platypus)

• Phylum :- Chordata (Dorsal tubular nerve cord, notochord and gill-slits present.)
• Group :- Craniata (Definite head, Cranium with brain present.)
• Sub phylum :- Vertebrata (Vertebral column present.)
• Division :- Gnathostomata (Jaws and paired appendages present.)
• Super Class :- Tetrapoda (Paired limbs, lungs, cornified skin and bony skeleton.)
• Class :- Mammalia (Body covered with hairs. Females have mammary glands.)
• Sub Class :- Prototheria (Egg-laying mammals.)
• Order :- Monotremata
• Genus :- Ornithorhynchus

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 metres along the river banks. It feeds on fresh-water invertebrates, carried in cheek pouches.

General Characteristics of Ornithorhynchus (Platypus)

• Commonly called as duck-billed-platypus.
• It measures about 50 cm in length having fine short fur, dark brown colour and combines the characters of a duck with a mammal.
• Body is divided into head, thick trunk and tail. Body and tail contain soft hairs.
• 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 nostril mouth and external ear opening.
• Adult has no teeth. Jaws covered with horny plates. Pinnae absent.
• Forelimbs and hind limbs have 5 digits, web and clawed toes.
• Hind limb has horny spur. Tail is flattened and adapted for swimming.
• Coracoid and precoracoid present. T -shaped interclavicle.
• Eyes small having nictitating membrane. Mammary glands without nipples.
• Cloaca present. Ureters open in dorsal wall of urinogenital passage. Testes abdominal, penis conducts only sperms. Oviducts distinct, uterus or vagina absent.
• Female makes nest of roots and leaves during spring in burrows, lays 1-3 eggs. About 0.5 cm long young one is hatched. It nurses by lapping up milk secreted by scattered mammary glands on the abdomen of female.

Special Features

Ornithorhynchus is an egg-laying mammal and 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 imperfect thermoregulator.

Identification

Since this mammal has flat bill and above features, hence it is Omithorhynchus