I must confess that before I started on my Hub on Australian Marsupials, I not only did not know of, or had ever actually heard of the word "monotreme".

Ok I hear you ask what is a monotreme, I hope this answers your question. 

It is widely accepted that Australia has the only two living examples in the world of the “monotreme”.

Before I show you these examples let me explain about the monotreme.

Monotremes lay eggs. OK big deal I hear you say, so do hens, but wait there IS more, and this is the facinating part.

The egg is retained for some time within the mother, who actively provides the egg with nutrients.

After the baby monotreme breaks away from the egg it is very small and vulnerable but still can find its way up to the mothers mammary glands to suckle.

Monotremes also lactate, but have no defined nipples, excreting the milk from their mammary glands via openings in their skin.

All species are long-lived, with low rates of reproduction and relatively prolonged parental care of infants.

More interesting facts about Monotremes

The monotremes also have extra bones in the shoulder girdle, including an interclavicle and coracoid, which are not found in other mammals. Monotremes retain a reptile-like gait, with legs that are on the sides of rather than underneath the body. The monotreme leg bears a spur in the ankle region.

The monotremes are the only mammals that do not experience REM sleep.

Their metabolic rate is remarkably low by mammalian standards. The monotreme has an  average body temperature of about 32 °C (90 °F) rather than the 37 °C (99 °F) typical of placental mammals.

Research suggests this has been a gradual adaptation to harsh environmental conditions on the part of the small number of surviving monotreme species rather than a historical characteristic of monotremes.

Like other mammals, monotremes are warm-blooded with a high metabolic rate (though not as high as other mammals); have hair on their bodies; produce milk, through mammary glands, to feed their young; have a single bone in their lower jaw; and have three middle ear bones.

Monotremes were very poorly understood for many years, and to this day some of the 19th century myths that grew up around them endure.

It is still sometimes thought, for example, that the monotremes are "inferior" or quasi-reptilian, and that they are a distant ancestor of the "superior" placental mammals.

It now seems plain 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.

Similarly, it is still sometimes said that monotremes have less developed internal temperature control mechanisms than other mammals, but it is now believed that monotremes maintain a constant body temperature in a wide variety of circumstances without difficulty, and are able to adjust their body temperature to suit the surrounding environment.

OK enough you say, lets cut to the chase. Australia's two examples of monotremes could not possibly look more different . They are The Platypus and the Echidna.

The Platypus (Ornithorhynchus anatinus) is a semi-aquatic mammal endemic to eastern Australia.

It is one of the species of monotremes, the only mammals that lay eggs instead of giving birth to live young. It is the sole living representative of its family (Ornithorhynchidae) and genus (Ornithorhynchus). The bizarre appearance of this egg-laying, venomous, duck-billed, beaver-tailed, otter-footed mammal baffled European naturalists when they first encountered it, with some considering it an elaborate fraud. When the Platypus was first discovered by Europeans in 1798, a pelt and sketch were sent back to the United Kingdom by Captain John Hunter, the second Governor of New South Wales. The British scientists were at first convinced that the samples must have been a hoax. Scientists, who produced the first description of the animal in 1799, stated that it was impossible not to entertain doubts as to its genuine nature, and believed it may have been produced by a taxidermist. It was thought that somebody had sewn a duck's beak onto the body of a beaver-like animal. One scientist even took a pair of scissors to the dried skin to check for stitches. The Platypus is one of the few venomous mammals, the male Platypus has a spur on the hind foot that delivers a venom capable of causing severe and lingering pain to humans. It is powerful enough to kill smaller animals such as dogs.

The Iconic Platypus.

The Platypus is the animal emblem of the state of New South Wales,and is featured on the reverse of the Australian 20 cent coin. The Platypus has been used several times as a mascot. "Syd" the Platypus was one of the three mascots chosen for the Sydney 2000 Olympics. "Expo Oz" the Platypus was the mascot for Expo '88, which was held in Brisbane in 1988.

Some interesting history.

Until the early 20th century it was hunted for its fur, but it is now fully protected and it's future is not under any immediate threat. There is no universally agreed upon plural of "platypus" in the English language. Scientists generally use "platypuses" or simply "platypus". Platypus Biology The body and the broad, flat tail of the Platypus are covered with dense brown fur that traps a layer of insulating air to keep the animal warm. The Platypus uses its tail for storage of fat reserves. It has webbed feet and a large, rubbery snout; these are features that appear closer to those of a duck than to those of any known mammal. The webbing is more significant on the front feet and is folded back when walking on land. Unlike a bird's beak (in which the upper and lower parts separate to reveal the mouth), the snout of the Platypus is a sensory organ with the mouth on the underside. The nostrils are located on the dorsal surface of the snout, while the eyes and ears are located in a groove set just back from it; this groove is closed when swimming. Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens. Weight varies considerably from 1.5 to 5.3 lb, with males being larger than females: males average 20inches total length while females average 17 inches. The species is endothermic, maintaining its body temperature about 90 °F, lower than most mammals, even while foraging for hours in water below 5 °C (41 °F).

Electroreception

Monotremes are the only mammals known to have a sense of electroreception:- they locate their prey in part by detecting electric fields generated by muscular contractions. The Platypus' electroreception is the most sensitive of any monotreme. The electroreceptors are located in rows in the skin of the bill, while mechanoreceptors (which detect touch) are uniformly distributed across the bill. The Platypuses brain recieves input signals from both elecroreceptors and mechanoreceptors indicating a close relationship between the tactile and electrical senses. The Platypus can determine the direction of an electric source, perhaps by comparing differences in signal strength across the sheet of electroreceptors. This would explain the animal's characteristic side-to-side motion of its head while hunting. The convergence of electrosensory and tactile inputs suggests a mechanism for determining the distance of prey items which, when they move, emit both electrical signals and mechanical pressure pulses, which would also allow for computation of distance from the difference in time of arrival of the two signals. The Platypus feeds by digging in the bottom of streams with its bill. The electroreceptors could be used to distinguish animate and inanimate objects in this situation (in which the mechanoreceptors would be continuously stimulated). When disturbed, its prey would generate tiny electrical currents in their muscular contractions which the sensitive electroreceptors of the Platypus could detect. Experiments have shown that the Platypus will even react to an "artificial shrimp" if a small electrical current is passed through it.

Longevity

In captivity, Platypuses have survived to seventeen years of age and wild specimens have been recaptured at eleven years old. Mortality rates for adults in the wild appear to be low. Natural predators include snakes, water rats, goannas, hawks, owls and eagles. Its habitat includes mainly rivers for both a food supply of prey species and banks where it can dig resting and nesting burrows. It may have a range of up to 4.3 miles, with male's home ranging to accomadate 3 or 4 females.

The Platypus is an excellent swimmer and spends much of its time in the water foraging for food. When swimming it can be distinguished from other Australian mammals by the absence of visible ears. Uniquely among mammals it propels itself when swimming by alternate rowing motion with the front two feet; although all four feet of the Platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail. Dives normally last between 30 - 40 seconds, but can last longer although few exceed the estimated aerobic limit of 40 seconds. 10 to 20 seconds are commonly spent in recovery at the surface.

The Platypus is a carnivore: it feeds on worms and insect larvae, freshwater shrimps, and yabbies that it digs out of the riverbed with its snout or catches while swimming. It utilises cheek-pouches to carry prey to the surface where they are eaten. The Platypus needs to eat about 20% of its own weight each day. This requires the Platypus to spend an average of 12 hours each day looking for food. When not in the water, the Platypus lives in a burrow, nearly always in the riverbank not far above water level, and often hidden under a protective tangle of roots.

The Baby Platypuses (Puggles)

Although not official of this writing a strong push is on to call baby monotremes by the name "Puggles", and being such a cute name that's the one I'm sticking with for the moment!

Platypuses exhibit a single breeding season, mating usually occurs between June and October which in Australia is late winter early spring.

After mating, the female constructs a deeper, more elaborate burrow up to 66 ft long and blocked with plugs at intervals (which may act as a safeguard against rising waters or predators, or as a method of regulating humidity and temperature).

The male takes no part in caring for its young, and retreats to its yearlong burrow. The female softens the ground in the burrow with dead, folded, wet leaves and she fills the nest at the end of the tunnel with fallen leaves and reeds for bedding material.

This material is dragged to the nest by tucking it underneath her curled tail. The female Platypus lays one to three small, leathery eggs (similar to those of reptiles), that are about 0.43 in in diameter and slightly rounder than bird eggs. The eggs develop for about 28 days with only about 10 days of external incubation (in contrast to a chicken egg, which spends about 1 day in tract and 21 days externally). After laying her eggs, the female curls around them.

The incubation period is separated into three parts. In the first, the embryo has no functional organs and relies on the yolk sac for sustenance. The yolk is absorbed by the developing young.

During the second, the digits develop, and in the last, the egg tooth appears. The newly hatched young are vulnerable, blind, and hairless, and are fed by the mother's milk.

Although possessing mammary glands, the Platypus lacks teats. Instead, milk is released through pores in the skin. There are grooves on her abdomen that form pools of milk, allowing the young to lap it up. After they hatch, the offspring are suckled for three to four months.

During incubation and weaning, the mother initially only leaves the burrow for short periods to forage. When doing so, she creates a number of thin soil plugs along the length of burrow possibly to protect the young from predators; pushing past these on her return forces water from her fur and allows the burrow to remain dry.

After about five weeks, the mother begins to spend more time away from her young and at around four months the young emerge from the burrow.

The Last Word

The Platypus is sometimes jokingly referred to as proof that God has a sense of humour (at the beginning of the film Dogma, for example). Its unusual appearance has led to its featuring in many media, particularly in its native Australia.

The Platypus has been shown on our currency for example the 20 cent coin. 

Echidnas , also known as spiny anteaters,belong to the family of monotremes.

Together with the Platypus, they are the only surviving members of that order. Although their diet consists largely of ants and termites, they are not actually related to the anteater species.

They live in New Guinea and Australia. The Echidna is named after a monster in ancient Greek mythology.

Echidnas are small mammals that are covered with coarse hair and spines. Superficially they resemble the anteaters of South America, and other spiny mammals like hedgehogs and porcupines. They have snouts which have the functions of both the mouth and nose. Their snouts are elongated and slender. They have very short, strong limbs with large claws and are powerful diggers.

Echidnas have a tiny mouth and a toothless jaw. They feed by tearing open soft logs, anthills and the like, and use their long, sticky tongue which protrudes from their snout to collect their prey. The Short-beaked Echidna's diet consists largely of ants and termites, while the Zaglossus species typically eat worms and insect larvae.

The long-beaked echidnas have tiny spines on their tongues that help capture their meals. Echidnas and the Platypus are the only egg-laying mammals, known as monotremes. The female lays a single soft-shelled, leathery egg twenty-two days after mating and deposits it directly into her pouch. Hatching takes ten days; the young echidna, called a puggle, then sucks milk from the pores of the two milk patches (monotremes have no nipples) and remains in the pouch for forty-five to fifty-five days, at which time it starts to develop spines. The mother digs a nursery burrow and deposits the puggle, returning every five days to suckle it until it is weaned at seven months.

Male echidnas have a four-headed penis, but only two of the heads are used during mating. The other two heads "shut down" and do not grow in size. The heads used are swapped each time the mammal copulates.

The Echinda given the name “Millie” (for Millennium) also represented Australia as a mascot in the 2ooo Summer Olympics that were held in Sydney.

The Echidna also makes an appearance on the Australian $1.00 coin.