Why Odd Egg-Laying Mammals Still Exist Why Odd Egg-Laying Mammals Still Exist By Charles Q. Choi, Live Science Contributor | September 21, 2009 11:06am ET MORE The platypus, found only in Australia is one of the five mammal species of that lay eggs instead of giving birth to live young. The other egg-laying mammals are four species of echidna. Credit: Gerry Pearce, australian-wildlife.com. The reason that odd, egg-laying mammals still exist today may be because their ancestors took to the water, scientists now suggest. The egg-laying mammals — the monotremes, including the platypus and spiny anteaters — are eccentric relatives to the rest of mammals, which bear live young. In addition to laying eggs, other quirks make them seem more like reptiles than our kin. They have a reptilian gait with legs on the sides rather than underneath the body, for instance, and a single duct for urine, feces and sex instead of multiple openings. These oddballs are often considered primitive "living fossils" that shed light on what our distant ancestors might have looked like.

Australian invasion Long ago, monotremes and their close relatives were the dominant mammals in the whole of Australia. Now only two kinds of monotremes are left on the planet — the duck-billed platypuses and the four species of echidnas, or spiny anteaters. Like all mammals, they possess hair, milk, sweat glands, three middle ear bones and a brain region known as the neocortex. The monotremes were almost totally swept aside when their pouch-bearing marsupial cousins — modern examples of which include the kangaroos — invaded Australia 71 million to 54 million years ago. Marsupials appear to have a number of advantages over monotremes — their bodies seem more efficient at locomotion, and the fact that they give birth to live offspring could provide better care of young. Moreover, before the marsupials reached Australia, they had migrated from Asia to the Americas to Antarctica.

The struggle marsupials presumably had with all the animals on these continents during this journey might have primed them for competition, "while the Australian mammals [including monotremes] that went extinct upon the arrival of marsupials had for the most part been isolated in Australia for a very long time," explained researcher Matthew Phillips, an evolutionary biologist at the Australian National University in Canberra. All these strengths help explain why marsupials triumphed in Australia. The mystery then is why any monotremes survived. Swim for it! Now Phillips and his colleagues suggest that platypuses and echidnas lived on because their ancestors sought refuge where marsupials could not follow — the water. Platypuses are amphibious creatures, while echidnas — the anteaters — are terrestrial. However, new genetic evidence and comparisons with fossil monotremes suggests that echidnas only diverged from platypuses 19 to 48 million years ago. This means echidnas recently had semi-aquatic predecessors and only later recolonized the land.

A number of aspects of echidna biology are consistent with an amphibious platypus-like ancestor — a streamlined body, rearward-jutting hind limbs that could act as rudders, and the contours of a duck-like bill during embryonic development. "Platypus-like fossils are known from at least 61 million years ago. It was thought that the much shorter fossil record for echidnas, from about 13 million years ago, was just due to the patchy nature of the fossil record," Phillips said. Their new findings suggest "the lack of early echidna fossils was in fact because they simply had not evolved yet." The researchers conjecture that marsupials could not afford a substantial invasion of aquatic environments because when they are born, they need to suckle milk constantly for weeks; newborn marsupials could drown if their mothers ever had to venture into the water. Evidence fits These findings remove an apparent contradiction between fossil data and DNA evidence, said Zhe-Xi Luo, curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh.

Evolutionary biologist Peter Waddell at Purdue University at West Lafayette, Ind., explained that an earlier study based on early monotreme fossils had suggested the platypus and the echidna diverged more than 110 million years ago, while the molecular data suggested a far more recent divergence. "Matt Phillips and colleagues have reassessed both the fossil and molecular data and concluded that the platypus-echidna split is in fact relatively recent," said mammalogist Robin Beck at the American Museum of Natural History in New York. "To put it simply, the bones and the genes appear to be telling essentially the same story, which is reassuring." "Another interesting aspect of this study is that it suggests that the echidna evolved from an ancestor that was very like a modern platypus, despite the fact that echidnas and platypuses are anatomically very different," Beck added. "This hypothesis has been suggested before, but the current paper provides the most compelling evidence yet that this is what actually happened. Not only that, but paper suggests that the change from a platypus-like body form to an echidna-like body form appears to have happened surprisingly quickly, in less than 15 to 25 million years.

That such a major change in overall morphology could happen so quickly is intriguing." Open questions The hint that echidnas may have evolved after marsupials arrived in Australia "contradicts the common assumption that monotremes are living fossils just treading water in an evolutionary sense, and waiting to go extinct in the face of competition with 'superior' mammals, like marsupials," Phillips added. The fossil record of monotremes remains very incomplete, particularly between about 100 and 25 million years ago, Beck said, noting that fossils that fill this 75 million year gap "might be found in Australia, South America or even Antarctica. However, there are a number of fossil sites in Australia that are 20 to 25 million years old, and the results of the current paper suggest that echidnas evolved during this period. With luck, future expeditions to these sites will discover fossil echidnas that demonstrate the change from a platypus-like to an echidna-like body form." Since a trait often considered primitive — egg-laying — might actually have helped monotremes survive to the present day, future research could investigate whether the same holds for other characteristics of theirs.

For instance, their reptile-like shoulders are poor for running fast, but they provide strong bracing. This allows for huge shoulder and arm musculature for use in rapid maneuvering in the water for the platypus or digging for echidnas, Phillips said. The scientists detailed their findings online September 21 in the Proceedings of the National Academy of Sciences. Australia's egg-laying mammals provide clues to our earliest ancestor | Science | The Guardian I like the duck-billed platypus Because it is anomalous. I like the way it raises its family Partly birdly, partly mammaly. -OGDEN NASH The platypus is famous for being one of the world’s strangest animals. When specimens were first shipped back from Australia, it was thought to be a taxidermic hoax. “Of all the Mammalia yet known”, wrote George Shaw in 1799, assistant keeper of the natural history department at the British Museum, “it seems the most extraordinary in its conformation; exhibiting the perfect resemblance of the beak of a duck engrafted on the head of a quadruped.” Their strangeness is more than skin deep.

From its webbed toes to the tip of its fat tail, the platypus (Ornithorhynchus anatinus) is packed with features that whisper of their ancient lineage, while their fossils and DNA leave us wondering if they are really so weird, or if it might be the rest of us who are the oddballs? The platypus and its closest relative, the echidna , belong to an order of mammals called the monotremes (Monotremata). They are the only representatives of this group left, surviving among the marsupials of Australia, Tasmania and New Guinea. Like the marsupials and the largest mammal group alive today, the placental mammals, the monotremes are furry, warm-blooded, and produce milk. They also share skeletal mammal traits, such as a single bone in the lower jaw – the dentary – and three middle ear bones called the malleus, incus and stapes. But unlike other mammals alive today, they don’t gestate their young inside the womb, nor do they keep them in a pouch like the marsupials. Like our ancient reptilian cousins, they lay eggs.

Pinterest Long-beaked echidna ( Zaglossus bruijni) . Photograph: Stephen Richards/AP Monotreme means “single hole”, referring to the multi-purpose opening in their rear end used for both excretion and reproduction. This hole is called a cloaca, and is more commonly seen in reptiles, amphibians and birds than mammals (golden moles and tenrecs also have one, making them unique among placental mammals). When it comes to sex, monotremes party with a busy compliment of ten chromosomes – five X-chromosomes and five Y-chromosomes – and their X is more like the Z sex-chromosome of birds. Reptilian and bird resemblances continue in the bones, as monotremes retain a complex pectoral girdle: bones around the chest and shoulders that provide a frame for muscle attachments. This, and the arrangement of their sturdy limbs, gives the platypus and echidna an ungainly lizard-like gait; swinging their sprawled limbs out to the side as they move, rather than bringing them directly under the body like other mammals. Pinterest Echidnas “trailing” one another in Taronga Zoo.

You may be aware of the electro-sensory abilities of the platypus bill – the echidnas’ nose tip also retains this feature – but you may not know these little warriors have spurs on their heels. A male platypus can use these spurs to deliver painful venom to rival males or would-be attackers. We now know from genetic studies that the platypus has acquired its venom through alterations in the same genes as poisonous reptiles. While the monotremes are indeed warm-blooded, they like to play it cool: five degrees cooler than us at a chilled out 32C. Although platypuses and echidnas feed their young on milk like other mammals, they don’t have nipples. Their milk oozes from special glands in the skin and is lapped up by their offspring. To compensate for this less sanitary delivery system, monotreme milk is packed with a record-breaking number of antibacterial proteins. So what does this pick’n’mix of reptile, bird and mammal characteristics tell us about the very first mammals, our shared common ancestors? The ancestor of monotremes branched off from the rest of the mammals between 160 and 210 million years ago according to molecular studies.

So which characteristics come from a common ancestor we both share, and which may have evolved in the millions of years since we diverged? It turns out that many seemingly unique monotrematan traits may have been common in early mammals. The first mammals were almost certainly egg-layers - although direct fossil evidence of these fragile structures is yet to be found, and may never be. There’s a good chance they would therefore have possessed a cloaca. As for milk production, the first mammals had probably begun producing milk as suckling is linked to the evolution of deciduous dentition or “milk-teeth”; the pattern of tooth replacement that sees a first set of teeth being replaced by a permanent adult set. This deciduous dentition is one of the defining characteristics of mammals as a whole, also allowing for precise occlusion and complex food processing. The appearance of the nipple however, remains difficult to put your finger on. Pinterest Plaster cast of a platypus egg. Photograph: Elsa Panciroli/National Museums Scotland But what about the other traits of the monotreme: venom and low body temperature? There is evidence to suggest members of several different mammal groups had venomous spurs, or even venom in their bite.

The spur of the platypus sits on a small bone called the os calcaris, and this bone has been found in multituberculates, an extinct order of mammals more closely related to the rest of Mammalia than to Monotremata. It has been suggested that poisonous spurs may even be one of the defining traits of all the first mammals, with later families losing their spurs. Finding out the body temperature of early mammals is tricky, as this doesn’t preserve in the fossil record. It is thought that the mammal-like reptiles from which true mammals evolved had higher metabolic rates and body temperatures than their common ancestor with other reptiles. The first true mammals probably had a mix of warm-blooded, constant body temperature interspersed with daily, or even seasonal, torpor or hibernation. The echidna has been used as a modern example of this, as it can effectively turn off its inner thermostat to conserve energy during extremes of temperature. The platypuses and echidna, animals we see as strange outliers among mammals today, are in many ways more akin to the original mammal blueprint than the rest of us.

Had the luck of the evolutionary draw been different, and monotremes dominated mammal life on earth instead of us placentals, Dr. P. Latypus may have received a strange package from abroad with the first placental mammal specimen, and been flummoxed by this weird, spurless creature that can’t even lay eggs. She may even have thought it was a hoax. References Warren, W. C., Hillier, L. W., Marshall Graves, J. A., Birney, E., Ponting, C. P., Grützner, F., … Wilson, R. K. (2008) Genome analysis of the platypus reveals unique signatures of evolution. Nature, 453(7192), 175–183. Whittington, C. M., Papenfuss, A. T., Bansal, P., Torres, A. M., Wong, E. S. W., Deakin, J. E., … Belov, K. (2008) Defensins and the convergent evolution of platypus and reptile venom genes.

Genome Research, 18(6), 986–994. Grigg, G., Beard, L., & Augee, M. (2004) The Evolution of Endothermy and Its Diversity in Mammals and Birds. Physiological and Biochemical Zoology: Ecological and Evolutionary Approaches, 77(6), 982-997. Lovegrove, B. G. (2012) The evolution of endothermy in Cenozoic mammals: a plesiomorphic‐apomorphic continuum. Biological Reviews, 87.1, 128-162. Mammals of Australia Australian Aboriginals had been accustomed to them for millennia, but early white explorers were amazed by what they found in Australia, and even today we are uncovering more and more remarkable facts about our mammals What is so odd about Australian mammals?

Australia is the only continent (and one of the only two countries - the other being New Guinea) in the world to still have all three of the major groups of mammals : monotremes, marsupials and placentals Half of Australia's mammal species are marsupials (South America has a few dozen species - all in the opossum family - and a couple of species have found their way into North America, but Australia is the only continent to have such a diverse range or to have marsupials as their most common and conspicuous land mammals) It is the only country in the world to have platypus, kangaroos (although New Guinea and some neighbouring islands do have wallabies), koalas, wombats, marsupial "moles" and numbats It is the only continent other than Antarctica to not have native hoofed animals, or terrestrial native Carnivora (dogs, bears, cats, weasels etc., but we do have seals and sea lions) - the dingo appears to have arrived from Southeast Asia only about 4,000 years ago, probably with Indonesian traders.

It is also the only continent to have rainforests but no monkeys Not only do we have mobs of great, two-legged hopping herbivores taking the place of deer and cattle, but we have a strange little furry creature that swims, lays eggs, give milk to its young, has a venomous spur, and uses electricity to find its prey, also small predators that revel in mating encounters only to have all males die of stress-related conditions within three weeks, a spiny but furry animal that develops a pouch shortly before laying an egg ....

and much more The world's three great groups of mammals: monotremes, marsupials and placentals are all found in Australia Monotremes - egg-laying mammals (nowadays found only in Australia and New Guinea) Marsupials - babies born in embryonic condition and kept firmly attached to a teat in a pouch or nestled behind a protective skin-flap while developing further Placentals - unborn young are nourished by a placenta (just to confuse things, some marsupials also have a placenta) and born at a more advanced stage, some still naked, blind and unable to walk for a week or two, others able to run on their day of birth The short answer is a vertebrate that gives milk to its young. A more detailed response is that a mammal: is a vertebrate animal (i.e.

has a 'backbone' of vertebrae protecting the central nervous system stemming from the brain, similar to birds, reptiles, amphibians and fish) gives milk to its young, produced from mammary glands (quite different from the 'milk' regurgitated from pigeons to their young) - this is unique in the animal kingdom is usually hairy (with a kind of hair not found in other animals, quite a difference substance from that of caterpillars or spiders for instance) - although a few such as whales and hippos do not have much hair has a lower jaw consisting of a single pair of bones (one of the ways we can tell if a fossil was a mammal) controls its body temperature ('warm-blooded') by a number of physiological means (similar to birds) and uses a diaphragm to contract and expand its lungs for breathing (similar to birds, reptiles and adult amphibians). Monotremes Monotremes lay eggs but give milk to their young, are covered in fur, and share other characteristics of marsupial and placental mammals. Their body temperature is lower, and they can when need arises allow it to drop considerably to slow down metabolism.

Their locomotion has reptilian qualities, and the adults have no teeth. The name means one opening, which refers to the cloaca (similar to that of birds and reptiles) through which the eggs are laid as well as waste products being eliminated. Platypus are found only in Australia, but we share echidna with New Guinea ( three species over there, including our species). The first platypus skin to be taken to England was simply not believed - skeptics were convinced it was the work of a skilled taxidermist stitching various other animal parts together. And that was only because of its bizarre appearance. No one yet knew that this furry, milk-giving animal also laid eggs ( that discovery was to cause further furore , although Aboriginals had long known this fact), that the male had a venomous spur (making it the only known venomous mammal in the world), that they have the highest rate of REM sleep of any mammal, or that they seek their prey not by sight but by using their rubbery bill which is sensitive to electrical and other vibrations from the muscles of aquatic crustaceans, insects and other small creatures.

The white you see around the eyes when they forage are small patches of white fur - the eyes are closed while diving and pursuing prey. The echidna, though often mistakenly called a porcupine or thought of as an aberrant hedgehog, is no less strange. It also lays eggs although furry and milk-giving, and the female develops a pouch while pregnant - the young live there until they become too prickly! The long rubbery bill is a similar substance to that of the platypus bill, and is used in procuring ants and termites from their nests. There is just one species in Australia, found also in New Guinea along with a further one to three species, depending which taxonomy is accepted (most commonly accepted nowadays seems to be dividing the long-beaked echdina into thee species - western, eastern and Attenborough's (or Sir David's)). Males (which incidentally have a strange, four-pronged penis) may sometimes be seen in the breeding season (winter) forming a 'love-train' in pursuit of a female, and soon both sexes start digging small trenches to facilitate mating.

That Steropodon galmani was a monotreme that lived amongst the dinosaurs in the early Creatceous, suggesting the group evolved within the Australian section of Gondwana in the Jurassic - they have certainly been in Australia a long time! There have also been fossilised platypus (different species to today's) found in Argentina - not surprising as Australia, Antarctica and Australia were still joined during the Cretaceous. They may have also had relatives in Madagascar, but fossil records are scarce and this hypothesis does not seem to currently hold much favour. It is thought that the echidna lineage evolved in Australia from platypus-like ancestry. Marsupials Marsupial young are born t a very elementary stage of development. This seems a but hard on Junior, but it's good for Mum - no long and heavy pregnancy. The tiny newborn - with mouth and arms well-developed but not much else - must climb all the way to the nipple and attach for the next few weeks.

There are also skeletal differences that are used to distinguish marsupial fossils from placentals Four orders of marsupial are now generally recognised in Australia and another two in South and Central America (opossums - one of which has reached North America - and shrew-opossums) The four orders of Australian marsupials are: Carnivorous marsupials: Tasmanian devils and their kin, plus the numbat and the now-extinct Thylacine Bandicoots and Bilbies Herbivorous marsupials: koala, wombat, possums, kangaroos and kin Marsupial "mole" (just one species - but strange enough to earn an order of its own) Carnivorous marsupials: (Dasyuromorphia) Tasmanian devils, quolls, dunnarts (the mouse-sized predator pictured to the right) and other members of family Dasyuridae have many sharp teeth on both upper and lower jaws, and relatively simple feet (compared with herbivorous marsupials).

Most species are rat-sized or smaller and all are nocturnal, so most Australian residents do not even notice their existence, except that ion some country areas the mouse-sized antechinuses enter houses in search of insects or winter warmth, and the larger phascogales (squirrel-size) or quolls (large cat-size) occasionally help themselves to chickens. The introduced cane toad is a serious threat to these larger species. The smaller members of the family go into a kind of frenzy of fighting (males) and mating in early spring, the couple staying physically coupled and active for several hours, then within the month all males die of stress-related disorders while the female lives on to raise her brood. The numbat has similar feet and basically similar dental structure but with highly reduced teeth due to specialisation for its diet of ants and termites.This attractive, alert and delightful little animal is sufficiently different to have a family of its own, and is now regrettably endangered, and confined to the south-west corner of Australia The wolf-like thylacine was also sufficiently different to have a family of its own. According to the fossil record there were several species, just one remaining by the time Aboriginals arrived in Australia.

After the dingo arrived (probably brought in by Indonesian traders around 3000 years ago) the thylacine became extinct on the mainland, but was still going strong in Tasmania, until white settlers arrived and found it was eating their chickens and sheep. By the time legislation was passed to protect it, it was too late, and the last known individual, Benjamin, died in captivity in 1936, on September 7th, a day that is now remembered each year as Threatened Species Day. Bandicoots and Bilbies (Peramelemorphia) This order appears to be half-way between the carnivorous and herbivorous groups in two ways: their diet is omnivorous - insects, fungi, roots etc. their teeth resemble those of the carnivorous marsupials but their hind feet have the syndactyly of the herbivorous marsupials (see below) Some bandicoot species are common, even appearing in suburban backyards, but others are threatened, by habitat loss, competition with rabbits, and predation by foxes and cats There were two species of the strange, rabbit-eared bilbies.

The lesser bilby has not been seen since the 1960's and is probably extinct, but the greater bilby , while till endangered, is now the subject of some very active campaigns to protect it. Herbivorous marsupials (Diprotodontia) This group is united by the following features: only one pair of incisors in the lower jaw syndactyly - the second and third toe of the hind foot being joined into a two-clawed grooming comb (they share this with the bandicoots and bilbies) This herbivorous order includes: Koala Kangaroos, wallabies and pademelons There is no sharp zoological division between kangaroos and wallabies. The three largest species were called kangaroos and most of the others are called wallabies regardless of how closely related they are to the species known as kangaroos.

The red kangaroo is very wide ranging in inland areas, from woodlands through to deserts The eastern grey kangaroo (pictured) is the only kangaroo seen on the east coast (and the only one in Tasmania), but is also found as far west as south-eastern South Australia in the outback The western grey kangaroo is found from Australia's south-west coast through to western Queensland, western Victoria and western New South Wales, their range thus overlapping with the eastern grey. They are darker and browner in colour than the eastern grey. Next in size to the kangaroos but still in the same genus (Macropus, meaning 'big foot') are two species of wallaroo (as though someone couldn't decide whether to call them kangaroos or wallabies) and the euro. Several wallabies are also in the same genus, and would have been called kangaroos if they had been big enough (thus there is no sharp scientific division between the terms 'kangaroo' and 'wallaby.' Pictured to the right is a red-necked wallaby, in the genus Macropus.

There are several other wallabies belonging to separate genera, such as the swamp wallaby, the nail-tailed wallabies, the hare-wallabies and the rock-wallabies (pictured to the left is the brush-tailed rock-wallaby). Tree kangaroos are true members of the kangaroo family (but not in the kangaroo genus) that have adapted to life in the trees in the rainforests of far north Queensland and New Guinea. There used to be more species in Australia in the geological past when rainforests were more extensive, and nowadays we have have only two, while several species still occur in New Guinea. They hop like 'normal' kangaroos along the branches and on the ground. Pademelons are small wallabies of the east coast living in dense forests that would impede the leaping ability of some of the larger species. Quokkas are wallabies from the south-west of Australia, nowadays mostly on Rottnest Island near Perth Conservation note: A number of species of small wallaby are now threatened because of habitat destruction and feral predators (the kangaroos and larger wallabies are locally threatened in some areas but the species are nowhere near as endangered as some of these smaller wallabies).

Potoroos, bettongs and rat-kangaroos These are small relatives of kangaroos and wallabies, possibly a similar size to the early kangaroo ancestors about 15 million years ago. The musky rat kangaroo is one of the few marsupials active during daylight hours, and is found in the tropical rainforests of far north Queensland, where it is an important disperser of seeds. They have prehensile tails, with which they carry foods and nesting material. The desert rat-kangaroo (not closely related to the musky) was by contrast an animal of extreme arid lands of the outback but is now probably extinct. Potoroos (see photo to left) are found in rainforests and eucalypt forests, and are important dispersers of miccorhyzal fungi (fungi which live in a symbiotic relationship with roots of forest trees: they process certain minerals in such a way as to make them much easier for the roots to absorb, and in turn get structural support from the roots). There were three species but now only two.

There are several species of bettongs (some endangered), collectively found throughout Australia but each restricted to particular habitats Possums and gliders There are four "super-families" of diprotodont marsupials collectively containing the families of animals we collectively call possums (none of which resemble the opossums of the Americas - a totally different group of marsupials) : * Pygmy possums (Burramyoidea) * Ring-tail possums, striped possum, Leadbeaters possum and several gliding possums (Petauroidea) * Brush-tail possums, cuscuses and scaly-tailed possum (Phalangeroidea) * Honey possum and feather-tailed glider (Tarsipedoidea: some dispute the close relationship of these species) Wombats There are three species of wombat - the common wombat found in south-eastern Australia including Tasmania, and two much rarer species, the southern hairy-nosed wombat of outback South Australia and the highly-endangered northern hairy-nosed wombat of outback Queensland (which used to also be found in parts of New South Wales but is now extinct there).

They are powerful burrowers, and live mainly on grasses. An oddity is their droppings, which are cubic - this appears to be so that a wombat can leave a deposit to mark his territory on new objects that appear within it - a deposit that will not roll off as readily as a round one would. Koala The closest living relatives of the koala are the wombats (turn a wombat 90 degrees, put it in a tree and give it fluffy ears and it would almost look like one). It is unusual for a tree-climbing animal to lack a tail, so it seems probable that the ancestors of both were ground-dwelling animals, and the koala secondarily moved back into the trees. In the geological past there were several species of koala, but there is now only one, although there are a few different races. They have a very restrictive diet, eating only the leaves of Eucalyptus and Corymbia species (Corymbia are so similar to Eucalyptus that until recent years they were include in the same genus), and not just any species even of these.

Eucalypt leaves are difficult to get all one's nourishment from - they have low levels of nitrogen, they have many indigestible chemicals, and only the young leaves are tender. There are only a couple of dozen species koalas regularly eat, and in any particular area within Australia there are usually less than half a dozen species the koalas will eat. Marsupial "mole" (Notoryctemorphia) This odd little animal is sufficiently different from other marsupials to have a whole taxonomic order to itself. It looks remarkably like the golden mole of Africa, and behaves in a somewhat similar way, but they are not at all closely related: they just have very similar lifestyles and have adapted in similar ways (but of course the golden mole is a placental, its young are thus born at a more advanced stage and they are not kept in a pouch). The marsupial 'mole' (since we don't yet seem to have a better common name for it) has a beautiful golden coat but is seldom seen, as it spends most of its time underground in remote areas of the outback. Placentals Australia has NO native placental carnivores (i.e.

cats, dogs, bears, raccoons etc - the dingo, now known as "Australia's wild dog", was introduced about 3000 years ago), NO native hoofed animals (deer, goats etc.) NO primates (monkeys and apes) and indeed NO native placentals except those listed below The native placentals we DO have are: whales and dolphins Bats Because they could fly, bats reached Australia quite early - at least 50 million years ago, and about a quarter of all native Australian mammal species are bats. Bats belong to two sub orders which are similar in having their fingers greatly extended and modified for flight but differ in some important ways: megabats (do not echo-locate but use sight, sound and smell in much the same way as most other mammals, usually eat fruit or nectar or both, and found from Africa to the South-west Pacific), microbats (echo-locate, usually eat insects, found on all continents). There is no evidence of the megabats being in Australia for more than about a million years.

Megabats These include the flying foxes (fruitbats:pictured above), the blossom bats and the tube-nosed bats, found in northern and eastern Australia. Because they do not echo-locate they do not need the elaborate nose-leaves and large ears the microbats usually have, but instead have more typically mammalian faces, leading to the common names 'flying fox' in English and 'flughund' in German. Their diet consists of fruit and nectar, some species favouring one more than the other. Microbats There are six families in Australia, and although some species are rare, collectively the microbats are very common throughout Australia, often a dozen or more species being found in any one locality. They are not, however, 'interchangeable.' Some prefer more open habitats to others, some forage above the canopy and others below, some catching insects from the water, some eating small vertebrates as well as insects, some able to keep hunting during winter while others can't, etc. Some sleep in caves, others in vegetation or old bird nests.

Rodents About a quarter of all native Australian mammal species are rodents (which comes as a surprise to many suburban Australians who usually only see the introduced rodent species). Three of the world has a higher proportion - about half the world's mammal species are rodents, but they entered Australia relatively recently, when Australia and New Guinea drifted close enough to south-east Asia for temporary land bridges to form). In Australia all native rodents are in the rats-and-mice family (i.e. there are no squirrels, porcupines, beavers etc. native to Australia). The ancestors of the native rats and mice appear to have arrived in Australia around 4 million years ago and have diversified since then into many different species, especially in drier regions (although several species are very common in our rainforests). Seals and sea lions Fur seals and sea-lions belong to the family Otariidae, and have visible ears. Two species of fur seals breed in Australia, and another two on Sub-Antarctic islands The Australian sea-lion is found only in Australia. Dugong The dugong is closely related to the manatees, and although a sea-dweller it is more closely related to elephants than to seals or whales.

It is unique amongst marine mammals in being entirely herbivorous. It is found from the coastal waters near Brisbane northwards, around the northern tropical waters and down the west coast to a point roughly level with Brisbane. It's numbers are regrettably declining. Whales and dolphins Several species of dolphin inhabit waters around Australia, the most common being the bottle-nosed dolphin Several shales migrate along the Australian coasts in winter, coming up from Antarctica to breed in warmer waters. The most commonly-seen in the south is the right whale, the most common on more northerly coasts being the humpback whale. References and links The Australian Museum Complete Book of Australian Mammals (Angus & Robertson, 1983) edited by R. Strahan has long been the standard reference to mammals of Australia. 'Mammals of Australia' by R. Strahan is a revision of this important document. Other books on Australian mammals include: Bryden, M. Marsh, H. and Shaughessy, P. (1998). Dugongs, Whales, Dolphins and Seals: a Guide to the Sea Mammals of Australia. Allen and Unwin, St Leonards Cronin, L.

1991. Key Guide to Australian Mammals. Reed Books Australia Hall, L. S. and Richards, G. C. 1979. Bats of Eastern Australia. Queensland Museum, Brisbane Johnson, P. 2003. Kangaroos of Queensland. Queensland Museum, Environmental Protection Agency of Queensland, With the generous support of Packers Associated Tanners Pty Ltd. Ride, W. D. L. 1970. A Guide to the Native Mammals of Australia. Oxford University Press, Melbourne Slater P. First Field Guide to Australian Mammals. Steve Parish Publishing. Slater P. Amazing Facts about Australian Mammals, Volume 2. Discover and Learn about Australia, Steve Parish (for children) Strahan, R. 1987. What Mammal is That? Angus and Robertson, Sydney Triggs, B. 1996. Tracks, Scats and Other Traces: a Field Guide to Australian Mammals.

Oxford University Press, Qld (very useful if the mammals themselves are not actually seen) See also these references to Australian mammal books The Australian Mammal Society was founded in 1958 to promote scientific study of the mammals of the Australian region. See also the Australian Museum's comprehensive pages on Australian mammals Introduction to the Monotremata Echidna. Photo by Dr. Lloyd Glenn Ingles © 2001 California Academy of Sciences. There are only five living monotreme species: the duck-billed platypus and four species of echidna (also known as spiny anteaters). All of them are found only in Australia and New Guinea. Monotremes are not a very diverse group today, and there has not been much fossil information known until rather recently. In some ways, monotremes are very primitive for mammals because, like reptiles and birds , they lay eggs rather than having live birth. In a number of other respects, monotremes are rather derived, having highly modified snouts or beaks, and modern adult monotremes have no teeth.

Like other mammals , however, monotremes have a single bone in their lower jaw, three middle ear bones, high metabolic rates, hair, and they produce milk to nourish the young. Click on the buttons below to learn more about Monotremes Read about monotremes at the University of Tasmania, who have one of the best sites on the web about living monotremes. Try the University of Michigan's Animal Diversity Web for more information about living monotremes. The Tasmanian Mammals page includes distributional information on monotremes. Egg-laying Mammals :: Saint Louis Zoo Saint Louis Zoo From desert to grassland to forests to alpine habitats Scientific Name Common Mammals That Lay Eggs? This animal may have sharp spines, but it isn't a porcupine! It's one of two types of primitive egg-laying mammals, or monotremes. (The other is the duck-billed platypus.) A Living Pincushion The first thing you probably notice about an echidna (pronounced ee-kid'-na) are the spines that cover most of its body, except for its face and belly.

The animal also has short fur in between its spines, as well as on its underside. The spines are a great protection against predators. When the echidna wedges itself in a hole or rolls up in a ball, it's almost impossible to attack this living pincushion! The echidna's long front claws might look scary too, but they're more useful in digging than in protection. There are two types of echidnas, short-beaked and long-beaked. The short-beaked is much smaller than its cousin, weighing from five to 15 lbs., with a length of 12 to 18 inches. (As the name implies, the long-beaked echidna has a longer, more downward curving beak. Its spines are shorter and they may be hidden by its longer fur.) Slurping its Supper With its long snout and powerful front legs, the body of an echidna seems tailor-made for slurping up its favorite foods: ants and termites. The animal also eats other insects and worms. An echidna uses its strong front claws and long stiff nose to plow through forest litter, break open ant- and termite-mounds, and overturn hollow logs.

Once it finds tasty bugs, it sucks them up with its long, sticky tongue. Because an echidna has no teeth, it grinds its food between the top of its mouth and the horny back of the tongue. Though they will usually take a daily meal, echidnas have been known to go for at least a month without eating. From Egg to Adult Echidnas and other monotremes are best known for the way their babies are born -- they hatch from eggs! But how do the babies begin? Breeding season in the wild is usually July and August (in captivity in the Northern Hemisphere, echidnas breed from December through February). Males begin the mating process: several of them engage in so-called 'train' behavior, in which they follow closely behind one female. Then the largest male will usually breed her several times during a one- or two-day mating period. A breeding female echidna develops a temporary pouch on her abdomen. When she deposits her single egg, she lays it directly into this pouch. The egg has a tan, leather-like shell. The egg incubates (develops) in the mother's pouch for 10 to11 days before the baby hatches.

When a baby echidna hatches, it is less than half-an-inch long, completely naked and helpless. It remains in the pouch for six to eight weeks, sucking the thick, yellowish milk known as "pap" from the mother's mammary glands. Since echidna pouches aren't as fully developed as the pouches of marsupial mammals (like kangaroos and koalas), the baby echidna has to hold on to its mother's pouch hairs to stay in place! Slowly, the baby's fur and spines begin to emerge through its pink skin. By the time the youngster is about 55 days old, it begins to feel "prickly" -- no wonder the mother ejects it from her pouch! She then deposits the baby in a nursery burrow she has dug, where it remains until it is weaned. Every few days, the mother returns to suckle the young. The baby is weaned at five months, when it emerges from the burrow and begins life on its own. I Want to be Alone Though their sharp spines may make them look scary, echidnas are shy, retiring animals.

They like to live alone; in fact, they don't show much social behavior. Echidnas don't engage in courtship, aggression, or maternal behaviors like many other mammals. One scientist says their behavior is not only simpler than that of most mammals, but than that of many lizards! Echidnas spend the day holed up in quiet shelters, which can range from shallow burrows to hollow logs to cavities under rocks or roots. Then they emerge late in the afternoon or at night to feed, depending on the daily temperatures and the time of year. When disturbed or alarmed, they have a variety of options to seek safety. Because they're strong diggers, they can burrow underground with amazing speed. They can also use their spines and feet to wedge themselves into crevices so that predators can't dislodge them. If all else fails, echidnas can roll up in a ball, leaving an attacker with a spiny dilemma. No Worries, Mate! Short-beaked echidnas are common throughout Australia, and their future seems rosy. Not so, however, for their close cousins in Papua New Guinea -- long-beaked echidnas. These animals are endangered because of habitat loss and hunting.

The Saint Louis Zoo is working with others to save this animal before it becomes extinct in the wild (see side story). Fun Facts Short-beaked echidnas are popular with zoos, since they are the only representative of egg-laying mammals established in captivity. These echidnas can live for more than 50 years in captivity. Echidnas have very poor eyesight, but they more than make up for this with excellent hearing. Class: Mammalia How the Venomous, Egg-Laying Platypus Evolved How the Venomous, Egg-Laying Platypus Evolved The odd Australian mammal has an intriguing family tree. View Images Platypuses hunt underwater, where they swim gracefully by paddling with their front webbed feet and steering with their hind feet and beaverlike tail. Photograph by Joel Sartore, National Geographic Photo Ark If there was a poster animal for diversification, it would have to be the platypus . It looks like an otter that’s gone trick-or-treating as a duck.

It’s a mashup that inspired Mark Anthony Libre to ask Weird Animal Question of the Week : "How did [the platypus] evolve in this unlikely fashion?” The platypus is an Australian mammal with some weirdly reptilian traits, like egg laying. While we think of mammals and reptiles as very different, at one time they shared a common ancestor, says Wes Warren of the Washington University School of Medicine in St. Louis. Probing Platypus Evolution February 6, 2009—National Geographic researchers are trying to collect DNA samples from these odd duck-billed mammals to determine whether there are separate subspecies. Warren led the 2008 study that found that the platypus has a "fascinating combination of reptilian and mammalian characters." (Related: " Platypus Genome Reveals Secrets of Mammalian Evolution .") Evolutionary Split War-Torn Yemen Is Letting Its Zoo Animals Starve to Death Mammal-like reptiles diverged from the lineage they shared with birds and reptiles about 280 million years ago.

Around 80 million years later, the monotremes—or egg-laying mammals—split off from the mammalian lineage, says Rebecca Young , a biologist at the University of Texas at Austin. View Images Venomous males have sharp stingers on the heels of their rear feet and can use them to deliver a strong blow. Photograph by Jean-Paul Ferrero, Minden Pictures All that remains of that branch of the family tree is the platypus and four species of echidna. (Related: " Which Animals Have Barely Evolved ?") This split happened before the evolution of the placenta, Young says, “so in that sense they are somewhere between a lizard and what we think of as a human-like placental mammal,” retaining some reptilian and mammalian features. Though monotremes' fossil record is limited , some skulls have been found, such as the extinct Obdurodon dicksoni . The creature, which lived during the Miocene period (about 23.3 million to 5.3 million years ago), has a similar snout to the modern-day platypus, but is likely not close kin .

While modern platypuses are down under, fossil evidence also shows that an ancient platypus lived in South America. View Images A zookeeper cradles rare twin platypus babies, which are known as puggles, at Healesville Sanctuary in Australia. Photograph by Jason Edwards, National Geographic Creative Your Electric Bill But why platypuses “stopped evolving and losing these components that make a mammal a mammal,” remains a mystery, says Warren. The platypus's milk seeps through pores in its abdomen, not through teats as in all other mammals. Another incredible adaptation is how they forage for food. Platypuses close their eyes, ears, and noses underwater and find prey by sensing electric currents with their ducklike bills. Their venom is located in a spur in the males' heels—a unique method of delivery among venomous creatures. (Also see " Venomous Primate Discovered in Borneo .") View Images These bottom feeders scoop up insects, larvae, shellfish, and worms in their bill along with bits of gravel and mud. Platypuses do not have teeth, so the bits of gravel help them to "chew" their meal.

Photograph by Dave Watts, Nature Picture Library Warren led a 2010 study that found 83 toxins in platypus venom , which contains genes that resemble the venom genes of other animals, including snakes, starfish, and spiders. It's likely an example of convergent evolution, in which unrelated species evolve similar traits. So while many things about the platypus remain mysterious. Young notes that there is "some randomness to how we acquire things over time," plus mutations and adaptations that happen more quickly. Weird Animal Question of the Week answers your questions every Saturday. If you have a question about the weird and wild animal world, tweet me , leave me a note or photo in the comments below, or find me on Facebook . Comment on This Story Platypus | National Geographic A platypus photographed at Healesville Sanctuary in Australia Photograph by Joel Sartore, National Geographic Photo Ark About the Platypus The platypus is among nature's most unlikely animals. In fact, the first scientists to examine a specimen believed they were the victims of a hoax.

The animal is best described as a hodgepodge of more familiar species: the duck (bill and webbed feet), beaver (tail), and otter (body and fur). Males are also venomous. They have sharp stingers on the heels of their rear feet and can use them to deliver a strong toxic blow to any foe. Platypuses in the Water Platypuses hunt underwater, where they swim gracefully by paddling with their front webbed feet and steering with their hind feet and beaverlike tail. Folds of skin cover their eyes and ears to prevent water from entering, and the nostrils close with a watertight seal. In this posture, a platypus can remain submerged for a minute or two and employ its sensitive bill to find food. These Australian mammals are bottom feeders. They scoop up insects and larvae, shellfish, and worms in their bill along with bits of gravel and mud from the bottom. All this material is stored in cheek pouches and, at the surface, mashed for consumption. Platypuses do not have teeth, so the bits of gravel help them to "chew" their meal.

Platypuses on Land On land, platypuses move a bit more awkwardly. However, the webbing on their feet retracts to expose individual nails and allow the creatures to run. Platypuses use their nails and feet to construct dirt burrows at the water's edge. Reproduction Platypus reproduction is nearly unique. It is one of only two mammals (the echidna is the other) that lay eggs. Females seal themselves inside one of the burrow's chambers to lay their eggs. A mother typically produces one or two eggs and keeps them warm by holding them between her body and her tail. The eggs hatch in about ten days, but platypus infants are the size of lima beans and totally helpless. Females nurse their young for three to four months until the babies can swim on their own. © 1996-Sat Jan 14 16:57:48 EST 2017 National Geographic Society.

Question: Which Australian mammal lays eggs?
Answer: Duck-billed platypus