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Platypus
Platypus
Source: David Dailey's Public Domain Images
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More About Platypuses ...
The Platypus (Ornithorhynchus anatinus) is a small, semi-aquatic mammal endemic to the eastern part of Australia, and one of the four extant monotremes, the only mammals that lay eggs instead of giving birth to live young (the other three are echidnas). It is the sole representative of its family (Ornithorhynchidae) and genus (Ornithorhynchus), though a number of fossilised relatives have been found, some of them also in the Ornithorhynchus genus.

The scientific name Ornithorhynchus literally means 'bird nose' in Greek, and anatinus means 'duck'. The common name means 'flat foot' and was originally given to it as a Linnaean genus name, but it was discovered to already belong to the wood-boring ambrosia beetle.

The body and the broad, flat tail of the Platypus are covered with brown fur. It has webbed feet and a large, rubbery snout that are more reminiscent of a duck than any other known mammal. (This has led to it being known as the 'Duckbilled Platypus'. Early British settlers called it the 'Water Mole'.)

Size varies considerably between less than a kilogramme and over two kilogrammes; with body length ranging from 30 to 40 centimetres, and tail length from 10 to 15 centimetres. Males are around one-third larger than females. There is substantial variation in average size from one region to another, though oddly this pattern does not seem to follow any particular climatic rule.

Modern Platypus young have tribosphenic 'three-cusped' molars, which are one of the hallmarks of mammals; adults are toothless. The Platypus jaw is constructed somewhat differently from that of other mammals, and the jaw opening muscle is different. As in all true mammals, the tiny bones that conduct sound to the inner ear are fully incorporated into the skull, rather than lying in the jaw as in cynodonts and other pre-mammalian synapsids. However, the external opening of the ear still lies at the base of the jaw. The Platypus has extra bones in the shoulder girdle, including an interclavicle, which is not found in other mammals. It also has a reptile-like gait, with legs that are on the sides of rather than underneath the body.

The Platypus is nocturnal and semi-aquatic, inhabiting small streams and rivers over an extensive range from the cold highlands of Tasmania and the Australian Alps to the tropical rainforests of coastal Queensland as far north as the base of the Cape York Peninsula. Inland, its distribution is not well known: it is extinct in South Australia (bar an introduced population on Kangaroo Island) and is no longer found in the main part of the Murray-Darling Basin, probably because of the declining water quality brought about by extensive land clearing and irrigation schemes. Along the coastal river systems, its distribution is unpredictable; it appears to be absent from some relatively healthy rivers, and yet maintains a presence in others that are quite degraded (the lower Maribyrnong, for example).

The Platypus is an excellent swimmer and spends much of its time in the water. It keeps its eyes tightly shut when swimming, relying completely on its other senses. All four feet of the Platypus are webbed. When it swims, it propels itself by paddling with the front two feet. The tail and hind feet assist in steering but not propulsion.

The Platypus is a carnivore. It feeds on worms and insect larvae, freshwater shrimps, and yabbies (freshwater crayfish) that it digs out of the river bed with its snout or catches while swimming. Its bill is very sensitive, allowing it to hunt its food without using sight. It is one of the few mammals known to have a sense of electroception: it locates its prey in part by detecting their body electricity. Its electroception is the most sensitive of any mammal.

When not in the water, the Platypus retires to a short, straight burrow of oval cross-section, nearly always in the riverbank not far above water level, and often hidden under a protective tangle of roots. For breeding, the female digs much larger and more elaborate burrows, up to 20 metres long and blocked with plugs at intervals. She fills the nest at the end of the tunnel with reeds for bedding material.

As a monotreme, the Platypus does not give birth to live young but instead lays eggs in its nest. The eggs are retained in the body for some time before they are laid, nourished actively by the parent. When the eggs hatch after an incubation period of roughly ten days, the small hairless babies cling to the mother. Like other mammals, the mother produces milk for the young. The Platypus does not have nipples, but excretes the milk through pores in her skin. The young suck milk up from the mother's belly while she lies on her back.

When the Platypus was first discovered by Europeans in the late 1700s, a pelt was sent back to Britain for examination by the scientific community. The British scientists were at first convinced that the seemingly odd collection of physical attributes must be a hoax, produced by some Asian taxidermist.

Much of the world was introduced to the Platypus in 1939 when National Geographic magazine published an article on the Platypus and the efforts to study and raise it in captivity. This is a very difficult task, and only a few young have been successfully raised since. (Notably at Healesville Sanctuary in Victoria.)

Seeing a Platypus in the wild is more a matter of luck and of patience than of difficulty. They tend to dislike populated areas, spend almost all their time underground or under water, and are primarily nocturnal. However, they are not especially uncommon, and in suitable areas most keen anglers or birdwatchers see a Platypus feeding quietly along a riverbank every year or two.

The Platypus does not appear to be in immediate danger of extinction. It is variously classified as secure but faces future threat or common but vulnerable, mainly because the species is sensitive to water pollution.

The Platypus and other monotremes were very poorly understood for many years, and to this day some of the 19th century myths that grew up around them endure, particularly in the northern hemisphere. It is still sometimes thought, for example, that the monotremes are 'inferior' or quasi-reptilian, and that they are the distant ancestor of the 'superior' placental mammals. It is now known that modern monotremes are the survivors of an early branching of the mammal tree; a later branching is thought to have led to the marsupial and placental groups. The oldest fossils of monotremes (Teinolophos and Steropodon are closely related to the modern Platypus. In summary, the Platypus is one of the closest relatives of ancestral mammals, but not itself a link in the chain of mammalian evolution. It is a branch quite separate from any other known one.
Taxonmony
Phylum: Chordata
Class: Mammalia
Order: Monotremata
Family: Ornithorhynchidae
Source: Wikipedia Read more about Platypuses
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