Misplaced Pages

#138861

74-410: The platypus ( Ornithorhynchus anatinus ), sometimes referred to as the duck-billed platypus , is a semiaquatic , egg-laying mammal endemic to eastern Australia , including Tasmania . The platypus is the sole living representative or monotypic taxon of its family Ornithorhynchidae and genus Ornithorhynchus , though a number of related species appear in the fossil record. Together with

148-467: A calcaneus spur on each hind limb. The female platypus, in common with echidnas, has rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands. Venom production rises among males during the breeding season, and it may be used to assert dominance. Similar spurs are found on many archaic mammal groups, indicating that this was an ancient general characteristic among mammals. Monotremes are

222-461: A mole . The platypus's tail stores fat reserves, an adaptation also found in the Tasmanian devil . Webbing is more significant on the front feet, which in land walking are folded up in knuckle-walking to protect the webbing. The elongated snout and lower jaw are covered in soft skin, forming the bill. The nostrils are located on the snout's dorsal surface, while the eyes and ears are just behind

296-449: A polygynous mating system. Females are believed to become sexually mature in their second year, with breeding observed in animals over nine years old. During copulation , the male grasps the female's tail with his bill, wraps his tail around her, then grips her neck or shoulder, everts his penis through his cloaca, and inserts it into her urogenital sinus . He takes no part in nesting, living in his year-long resting burrow. After mating,

370-481: A reptilian gait with legs on the sides of the body, rather than underneath. The platypus's genes are a possible evolutionary link between the mammalian XY and bird/reptile ZW sex-determination systems, as one of the platypus's five X chromosomes contains the DMRT1 gene, which birds possess on their Z chromosome. As in all true mammals, the tiny bones that conduct sound in the middle ear are fully incorporated into

444-427: A chicken egg, which spends about one day in tract and 21 days externally). The female curls around the incubating eggs, which develop in three phases. In the first, the embryo has no functional organs and relies on the yolk sac for sustenance, until the sac is absorbed. During the second phase, the digits develop, and in the last phase, the egg tooth appears. At first, European naturalists could hardly believe that

518-418: A different type of hair. Down hair (also known as underfur , undercoat , underhair or ground hair ) is the bottom – or inner – layer, composed of wavy or curly hairs with no straight portions or sharp points. Down hairs, which are also flat, tend to be the shortest and most numerous in the coat. Thermoregulation is the principal function of the down hair, which insulates

592-426: A large optic tectum , suggesting that the visual midbrain plays a more important role than the visual cortex , as in some rodents. These features suggest that the platypus has adapted to an aquatic and nocturnal lifestyle, developing its electrosensory system at the cost of its visual system. This contrasts with the small number of electroreceptors in the short-beaked echidna , which dwells in dry environments, while

666-419: A layer of dry air next to the skin. The awn hair can be thought of as a hybrid, bridging the gap between the distinctly different characteristics of down and guard hairs. Awn hairs begin their growth much like guard hairs, but less than halfway to their full length, awn hairs start to grow thin and wavy like down hair. The proximal part of the awn hair assists in thermoregulation (like the down hair), whereas

740-501: A nesting platypus was filmed inside the recently reopened sanctuary. There is a population on Kangaroo Island introduced in the 1920s, said to stand at 150 individuals in the Rocky River region of Flinders Chase National Park . In the 2019–20 Australian bushfire season , large portions of the island burnt, decimating wildlife. However, SA Department for Environment and Water recovery teams worked to reinstate their habitat, with

814-595: A number of sightings reported by April 2020. The platypus is no longer found in the main Murray–Darling Basin , possibly due to declining water quality from land clearing and irrigation although it is found in the Goulburn River in Victoria. Along the coastal river systems, its distribution is unpredictable: absent in some relatively healthy rivers, but present in some quite degraded ones, for example

SECTION 10

#1732772567139

888-440: A wide array of hard and soft-bodied prey, was outcompeted by the rakali over hard-bodied prey such as crayfish and mussels. This competition may have selected for the loss of teeth in the platypus and their replacement by horny pads, as a way of specializing for softer-bodied prey, which the rakali did not compete with it over. Because of the early divergence from the therian mammals and the low numbers of extant monotreme species,

962-655: Is larila . When the platypus was first encountered by Europeans in 1798, a pelt and sketch were sent back to Great Britain by Captain John Hunter , the second Governor of New South Wales . British scientists' initial hunch was that the attributes were a hoax. George Shaw , who produced the first description of the animal in the Naturalist's Miscellany in 1799, stated it was impossible not to entertain doubts as to its genuine nature, and Robert Knox believed it might have been produced by some Asian taxidermist . It

1036-403: Is composed largely of defensin -like proteins (DLPs) produced by the immune system, three of which are unique to the platypus. In other animals, defensins kill pathogenic bacteria and viruses, but in platypuses they are also collected into a venom against predators. Venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands connected by a thin-walled duct to

1110-492: Is constructed differently from that of other mammals, and the jaw-opening muscle is different. Modern platypus young have three teeth in each of the maxillae (one premolar and two molars ) and dentaries (three molars), which they lose before or just after leaving the breeding burrow; adults instead develop heavily keratinised food-grinding pads called ceratodontes . The first upper and third lower cheek teeth of platypus nestlings are small, each having one principal cusp, while

1184-417: Is driven largely by camouflage. Differences in female and male coat color may indicate nutrition and hormone levels, important in mate selection. Some arboreal mammals, notably primates and marsupials, have shades of violet, green, or blue skin on parts of their bodies, indicating some distinct advantage in their largely arboreal habitat due to convergent evolution . The green coloration of sloths, however,

1258-401: Is incorrect. In fact, modern monotremes are the survivors of an early branching of the mammal tree, and a later branching is thought to have led to the marsupial and placental groups. Molecular clock and fossil dating suggest platypuses split from echidnas around 19–48   million years ago. The oldest discovered fossil of the modern platypus dates back to about 100,000 years ago during

1332-479: Is no universally agreed plural form of "platypus" in the English language. Scientists generally use "platypuses" or simply "platypus". Alternatively, the term "platypi" is also used for the plural, although this is a form of pseudo-Latin ; going by the word's Greek roots the plural would be "platypodes". Early British settlers called it by many names, such as "watermole", "duckbill", and "duckmole". Occasionally it

1406-462: Is specifically called the "duck-billed platypus". The scientific name Ornithorhynchus anatinus literally means 'duck-like bird-snout', deriving its genus name from the Greek root ornith- ( όρνιθ ornith or ὄρνις órnīs 'bird') and the word rhúnkhos ( ῥύγχος 'snout', 'beak'). Its species name is derived from Latin anatinus ('duck-like') from anas 'duck'. The platypus

1480-445: Is the result of a symbiotic relationship with algae. Coat color is sometimes sexually dimorphic , as in many primate species . Coat color may influence the ability to retain heat, depending on how much light is reflected. Mammals with darker colored coats can absorb more heat from solar radiation and stay warmer; some smaller mammals, such as voles , have darker fur in the winter. The white, pigmentless fur of arctic mammals, such as

1554-438: Is the sole living representative or monotypic taxon of its family (Ornithorhynchidae). In David Collins 's account of the new colony 1788–1801, he describes "an amphibious animal, of the mole species", with a drawing. The body and the broad, flat tail of the platypus are covered with dense, brown, biofluorescent fur that traps a layer of insulating air to keep the animal warm. The fur is waterproof, and textured like that of

SECTION 20

#1732772567139

1628-1137: The IUCN , but a November 2020 report has recommended that it be upgraded to threatened species under the federal EPBC Act , due to habitat destruction and declining numbers in all states. Australian Aboriginal people name or have named the platypus in various ways depending on Australian indigenous languages and dialects . Among the names found: boondaburra , mallingong , tambreet , watjarang (names in Yass , Murrumbidgee , and Tumut ), tohunbuck (region of Goomburra , Darling Downs ), dulaiwarrung ou dulai warrung ( Woiwurrung language, Wurundjeri , Victoria ), djanbang ( Bundjalung , Queensland ), djumulung ( Yuin language, Yuin , New South Wales ), maluŋgaŋ (ngunnawal language, Ngunnawal , Australian Capital Territory ), biladurang , wamul , dyiimalung , oornie , dungidany ( Wiradjuri language, Wiradjuri , Vic , NSW ), oonah , etc. The name chosen and approved in Palawa kani (reconstructed tasmanian language)

1702-523: The Linnaean name Platypus anatinus when he described it, but the genus term was quickly discovered to already be in use as the name of the wood-boring ambrosia beetle genus Platypus . It was independently described as Ornithorhynchus paradoxus by Johann Blumenbach in 1800 (from a specimen given to him by Sir Joseph Banks ) and following the rules of priority of nomenclature, it was later officially recognised as Ornithorhynchus anatinus . There

1776-483: The Miocene of Australia. It closely resembled the modern platypus, aside from the presence of molar teeth. A fossilised tooth of the giant platypus Obdurodon tharalkooschild was dated 5–15   million years ago. Judging by the tooth, the animal measured 1.3 metres long, making it the largest platypus on record. The loss of teeth in the modern platypus has long been enigmatic, as a distinctive lower molar tooth row

1850-607: The Quaternary period, though a limb bone of Ornithorhynchus is known from Pliocene -aged strata. The extinct monotremes Teinolophos and Steropodon from the Cretaceous were once thought to be closely related to the modern platypus, but are now considered more basal taxa. The fossilised Steropodon was discovered in New South Wales and is composed of an opalised lower jawbone with three molar teeth (whereas

1924-674: The Sphynx cat . Similarly, there are some breeds of hairless dogs . Other examples of artificially selected hairless animals include the hairless guinea-pig , nude mouse , and the hairless rat . Fur has long served as a source of clothing for humans, including Neanderthals . Historically, it was worn for its insulating quality, with aesthetics becoming a factor over time. Pelts were worn in or out, depending on their characteristics and desired use. Today fur and trim used in garments may be dyed bright colors or to mimic exotic animal patterns, or shorn close like velvet . The term "a fur" may connote

1998-499: The distal part can shed water (like the guard hair). The awn hair's thin basal portion does not allow the amount of piloerection that the stiffer guard hairs are capable of. Mammals with well-developed down and guard hairs also usually have large numbers of awn hairs, which may even sometimes be the bulk of the visible coat. Guard hair ( overhair ) is the top—or outer—layer of the coat. Guard hairs are longer, generally coarser, and have nearly straight shafts that protrude through

2072-542: The fur industry as a furbearer . The use of fur as clothing or decoration is controversial; animal welfare advocates object to the trapping and killing of wildlife, and the confinement and killing of animals on fur farms . The modern mammalian fur arrangement is known to have occurred as far back as docodonts , haramiyidans and eutriconodonts , with specimens of Castorocauda , Megaconus and Spinolestes preserving compound follicles with both guard hair and underfur. Fur may consist of three layers, each with

2146-508: The long-beaked echidna , which lives in moist environments, is intermediate between the other two monotremes. In 2020, research revealed that platypus fur gives a bluish-green biofluorescent glow in black light . The platypus is semiaquatic, 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

2220-522: The muskox has guard hairs measuring 30 cm (12 in) as well as a dense underfur, which forms an airtight coat, allowing them to survive in temperatures of −40 °C (−40 °F). Some desert mammals, such as camels, use dense fur to prevent solar heat from reaching their skin, allowing the animal to stay cool; a camel's fur may reach 70 °C (158 °F) in the summer, but the skin stays at 40 °C (104 °F). Aquatic mammals , conversely, trap air in their fur to conserve heat by keeping

2294-479: The reverse of the Australian twenty-cent coin , and is an emblem of the state of New South Wales . The platypus was hunted for its fur, but it has been a legally protected species in all states where it occurs since 1912. Its population is not under severe threat, although captive-breeding programs have had slight success, and it is vulnerable to pollution. It is classified as a near-threatened species by

Platypus - Misplaced Pages Continue

2368-399: The 19th century myths that grew up around them – for example, that the monotremes were "inferior" or quasireptilian  – still endure. In 1947, William King Gregory theorised that placental mammals and marsupials may have diverged earlier, and a subsequent branching divided the monotremes and marsupials, but later research and fossil discoveries have suggested this

2442-404: The 37 °C (99 °F) typical of placental mammals . Research suggests this has been a gradual adaptation to harsh environmental conditions among the few marginal surviving monotreme species, rather than a general characteristic of past monotremes. In addition to laying eggs, the anatomy, ontogeny , and genetics of monotremes shows traces of similarity to reptiles and birds. The platypus has

2516-473: The adult contemporary platypus is toothless). The molar teeth were initially thought to be tribosphenic , which would have supported a variation of Gregory's theory, but later research has suggested, while they have three cusps, they evolved under a separate process. The fossil jaw of Teinolophos is thought to be about 110   million years old, making it the oldest mammal fossil found in Australia. Unlike

2590-432: The animal's head while hunting. It may also be able to determine the distance of moving prey from the time lag between their electrical and mechanical pressure pulses. Monotreme electrolocation for hunting in murky waters may be tied to their tooth loss. The extinct Obdurodon was electroreceptive, but unlike the modern platypus it foraged pelagically (near the ocean surface). In recent studies it has been suggested that

2664-690: The base of the Cape York Peninsula . Inland, its distribution is not well known. It was considered extinct on the South Australian mainland, with the last sighting recorded at Renmark in 1975. In the 1980s, John Wamsley created a platypus breeding program in Warrawong Sanctuary (see below ), which subsequently closed. In 2017 there were some unconfirmed sightings downstream from the sanctuary, and in October 2020

2738-431: The black-and-white pelage of many mammals which are able to defend themselves, such as in the foul-smelling skunk and the powerful and aggressive honey badger . In arctic and subarctic mammals such as the arctic fox ( Vulpes lagopus ), collared lemming ( Dicrostonyx groenlandicus ), stoat ( Mustela erminea ), and snowshoe hare ( Lepus americanus ), seasonal color change between brown in summer and white in winter

2812-420: 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. A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates it uses to grind food. Platypus Echidnas Marsupials Eutherians The platypus and other monotremes were very poorly understood, and some of

2886-434: The egg's cytoplasm, allowing the yolk and embryo to exchange waste and nutrients with the egg through the cytoplasm. Young platypus are called "puggles". Newly hatched platypuses are vulnerable, blind, and hairless, and are fed by the mother's milk, that provides all the requirements for growth and development. The platypus's mammary glands lack teats, with milk released through pores in the skin. The milk pools in grooves on

2960-409: The eyes of the platypus are more similar to those of Pacific hagfish or Northern Hemisphere lampreys than to those of most tetrapods. The eyes also contain double cones , unlike most mammals. Although the platypus's eyes are small and not used under water, several features indicate that vision was important for its ancestors. The corneal surface and the adjacent surface of the lens is flat, while

3034-641: The female constructs a deep, elaborate nesting burrow up to 20 m (65 ft) long. She tucks fallen leaves and reeds underneath her curled tail, dragging them to the burrow to soften the tunnel floor with folded wet leaves, and to line the nest at the end with bedding. The female has two ovaries , but only the left one is functional. She lays one to three (usually two) small, leathery eggs (similar to those of reptiles), about 11 mm ( 7 ⁄ 16  in) in diameter and slightly rounder than bird eggs. The eggs develop in utero for about 28 days, with only about 10 days of external incubation (in contrast to

Platypus - Misplaced Pages Continue

3108-409: The female platypus lays eggs, but this was finally confirmed by William Hay Caldwell in 1884. Most mammal zygotes go through holoblastic cleavage, splitting into multiple divisible daughter cells. However, monotremes like the platypus, along with reptiles and birds , undergo meroblastic cleavage, in which the ovum does not split completely. The cells at the edge of the yolk remain continuous with

3182-409: The first scientists to examine a preserved platypus body judged it a fake made of several animals sewn together. The unique features of the platypus make it important in the study of evolutionary biology , and a recognisable and iconic symbol of Australia . It is culturally significant to several Aboriginal peoples , who also used to hunt it for food. It has appeared as a national mascot, features on

3256-559: The four species of echidna , it is one of the five extant species of monotremes , mammals that lay eggs instead of giving birth to live young. Like other monotremes, the platypus has a sense of electrolocation , which it uses to detect prey in cloudy water. It is one of the few species of venomous mammals , as the male platypus has a spur on the hind foot that delivers an extremely painful venom . The unusual appearance of this egg-laying, duck -billed, beaver -tailed, otter -footed mammal at first baffled European naturalists. In 1799,

3330-418: The gene HR can lead to complete hair loss , though this is not typical in humans. At times, when a hairless domesticated animal is discovered, usually owing to a naturally occurring genetic mutation, humans may intentionally inbreed those hairless individuals and, after multiple generations, artificially create hairless breeds. There are several breeds of hairless cats, perhaps the most commonly known being

3404-476: The largest extant terrestrial mammals, the elephant and the rhinoceros , are largely hairless. The hairless bat is mostly hairless but does have short bristly hairs around its neck, on its front toes, and around the throat sac, along with fine hairs on the head and tail membrane. Most hairless animals cannot go in the sun for long periods of time, or stay in the cold for too long. Marsupials are born hairless and grow out fur later in development. Humans are

3478-421: The layer of softer down hair. The distal end of the guard hair is the visible layer of most mammal coats. This layer has the most marked pigmentation and gloss , manifesting as coat markings that are adapted for camouflage or display. Guard hair repels water and blocks sunlight, protecting the undercoat and skin in wet or aquatic habitats, and from the sun's ultraviolet radiation. Guard hairs can also reduce

3552-486: The lower Maribyrnong . In captivity, platypuses have survived to 30 years of age, and wild specimens have been recaptured when 24 years old. Mortality rates for adults in the wild appear to be low. Natural predators include snakes , water rats , goannas , hawks , owls , and eagles . Low platypus numbers in northern Australia are possibly due to predation by crocodiles . The introduction of red foxes in 1845 for sport hunting may have had some impact on its numbers on

3626-430: The mainland. The platypus is generally nocturnal and crepuscular , but can be active on overcast days. Its habitat bridges rivers and the riparian zone , where it finds both prey and river banks to dig resting and nesting burrows. It may have a range of up to 7 km (4.3 mi), with a male's home range overlapping those of three or four females. The platypus is an excellent swimmer and spends much of its time in

3700-573: The modern platypus (and echidnas ), Teinolophos lacked a beak. In 2024, Late Cretaceous ( Cenomanian )-aged fossil specimens of actual early platypus relatives were recovered from the same rocks as Steropodon , including the basal Opalios and the more derived Dharragarra , the latter of which may be the oldest member of the platypus stem -lineage, as it retains the same dental formula found in Cenozoic platypus relatives. Monotrematum and Patagorhynchus , two other fossil relatives of

3774-431: The mother's abdomen, allowing the young to lap it up. After they hatch, the offspring are milk-fed for three to four months. During incubation and weaning, the mother initially leaves the burrow only for short periods to forage. She leaves behind her a number of thin soil plugs along the length of the burrow, possibly to protect the young from predators; pushing past these on her return squeezes water from her fur and allows

SECTION 50

#1732772567139

3848-484: The only primate species that have undergone significant hair loss. The hairlessness of humans compared to related species may be due to loss of functionality in the pseudogene KRTHAP1 (which helps produce keratin ) Although the researchers dated the mutation to 240 000 ya, both the Altai Neandertal and Denisovan peoples possessed the loss-of-function mutation, indicating it is much older. Mutations in

3922-559: The only mammals (apart from the Guiana dolphin ) known to have a sense of electroreception , and the platypus's electroreception is the most sensitive of any monotreme. Feeding by neither sight nor smell, the platypus closes its eyes, ears, and nose when it dives. Digging in the bottom of streams with its bill, its electroreceptors detect tiny electric currents generated by the muscular contractions of its prey, enabling it to distinguish between animate and inanimate objects. Experiments have shown

3996-496: The other teeth have two main cusps. While both male and female platypuses are born with back ankle spurs, only the males' deliver venom. It is powerful enough to kill smaller animals such as dogs, and though it is not lethal to humans, it can inflict weeks of agony. Edema rapidly develops around the wound and gradually spreads through the affected limb, and it may develop into an excruciating hyperalgesia (heightened sensitivity to pain) persisting for days or even months. The venom

4070-460: The platypus feels electric fields like touches. These receptors in the bill dominate the somatotopic map of the platypus brain, in the same way human hands dominate the Penfield homunculus map . The platypus can feel the direction of an electric source, perhaps by comparing differences in signal strength across the sheet of electroreceptors, enhanced by the characteristic side-to-side motion of

4144-664: The platypus has great homology to the bird Z chromosome. The platypus genome also has both reptilian and mammalian genes associated with egg fertilisation. Though the platypus lacks the mammalian sex-determining gene SRY , a study found that the mechanism of sex determination is the AMH gene on the oldest Y chromosome . A draft version of the platypus genome sequence was published in Nature on 8   May 2008, revealing both reptilian and mammalian elements, as well as two genes found previously only in birds, amphibians, and fish. More than 80% of

4218-499: The platypus is a frequent subject of research in evolutionary biology. In 2004, researchers at the Australian National University discovered the platypus has ten sex chromosomes , compared with two (XY) in most other mammals. These ten chromosomes form five unique pairs of XY in males and XX in females, i.e. males are X 1 Y 1 X 2 Y 2 X 3 Y 3 X 4 Y 4 X 5 Y 5 . One of the X chromosomes of

4292-452: The platypus will even react to an "artificial shrimp" if a small electric current is passed through it. The electroreceptors are located in rostrocaudal rows in the skin of the bill, while mechanoreceptors for touch are uniformly distributed across the bill. The electrosensory area of the cerebral cortex is in the tactile somatosensory area, and some cortical cells receive input from both electroreceptors and mechanoreceptors, suggesting

4366-409: The platypus's genes are common to the other mammals whose genomes have been sequenced. An updated genome, the most complete on record, was published in 2021, together with the genome of the short-beaked echidna . Semiaquatic In biology , being semi-aquatic refers to various macro organisms that live regularly in both aquatic and terrestrial environments . When referring to animals ,

4440-421: The platypus, are known from the latest Cretaceous ( Maastrichtian ) and the mid- Paleocene of Argentina , indicating that some monotremes managed to colonize South America from Australia when the two continents were connected via Antarctica . These are also considered potential members of the platypus stem-lineage. The closest fossil relative of the platypus was Obdurodon , known from the late Oligocene to

4514-591: The polar bear, may reflect more solar radiation directly onto the skin. The term pelage  – first known use in English c.  1828 (French, from Middle French, from poil for 'hair', from Old French peilss , from Latin pilus ) – is sometimes used to refer to an animal's complete coat . The term fur is also used to refer to animal pelts that have been processed into leather with their hair still attached. The words fur or furry are also used, more casually, to refer to hair-like growths or formations, particularly when

SECTION 60

#1732772567139

4588-439: The posterior surface of the lens is steeply curved, similar to the eyes of other aquatic mammals such as otters and sea-lions. A temporal (ear side) concentration of retinal ganglion cells , important for binocular vision, indicates a vestigial role in predation , though the actual visual acuity is insufficient for such activities. Limited acuity is matched by low cortical magnification , a small lateral geniculate nucleus , and

4662-464: The primary usage being thermoregulation. The types of hair include Hair length is negligible in thermoregulation, as some tropical mammals, such as sloths, have the same fur length as some arctic mammals but with less insulation; and, conversely, other tropical mammals with short hair have the same insulating value as arctic mammals. The denseness of fur can increase an animal's insulation value, and arctic mammals especially have dense fur; for example,

4736-416: The riverbed with its snout or catches while swimming. It carries prey to the surface in cheek-pouches before eating it. It eats about 20% of its own weight each day, which requires it to spend an average of 12 hours daily looking for food. The species has a single breeding season between June and October, with some local variation. Investigations have found both resident and transient platypuses, and suggest

4810-717: The severity of cuts or scratches to the skin. Many mammals, such as the domestic dog and cat, have a pilomotor reflex that raises their guard hairs as part of a threat display when agitated. Hair is one of the defining characteristics of mammals; however, several species or breeds have considerably reduced amounts of fur. These are often called "naked" or "hairless". Some mammals naturally have reduced amounts of fur. Some semiaquatic or aquatic mammals such as cetaceans , pinnipeds and hippopotamuses have evolved hairlessness, presumably to reduce resistance through water. The naked mole-rat has evolved hairlessness, perhaps as an adaptation to their subterranean lifestyle. Two of

4884-413: The skin dry. Mammalian coats are colored for a variety of reasons, the major selective pressures including camouflage , sexual selection , communication, and physiological processes such as temperature regulation. Camouflage is a powerful influence in many mammals, as it helps to conceal individuals from predators or prey. Aposematism , warning off possible predators, is the most likely explanation of

4958-412: The skull, rather than lying in the jaw as in 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 not found in other mammals. As in many other aquatic and semiaquatic vertebrates , the bones show osteosclerosis , increasing their density to provide ballast. The platypus jaw

5032-640: The snout in a groove which closes underwater. Platypuses can give a low growl when disturbed, and a range of vocalisations have been reported in captivity. Size varies considerably in different regions, with average weight from 0.7 to 2.4 kg (1 lb 9 oz to 5 lb 5 oz); males have average length 50 cm (20 in), while females are the smaller at 43 cm (17 in). This variation does not seem to follow any particular climatic rule and may be due to other factors such as predation and human encroachment. The platypus has an average body temperature of about 32 °C (90 °F), lower than

5106-410: The subject being referred to exhibits a dense coat of fine, soft "hairs". If layered, rather than grown as a single coat , it may consist of short down hairs, long guard hairs , and in some cases, medium awn hairs . Mammals with reduced amounts of fur are often called "naked", as with the naked mole-rat , or "hairless", as with hairless dogs . An animal with commercially valuable fur is known within

5180-413: The surface between dives. The platypus rests in a short, straight burrow in the riverbank about 30 cm (12 in) above water level, its oval entrance-hole often hidden under a tangle of roots. It may sleep up to 14 hours per day, after half a day of diving. The platypus is a carnivore , feeding on annelid worms, insect larvae , freshwater shrimp , and yabby ( crayfish ) that it digs out of

5254-759: The term describes those that actively spend part of their daily time in water (in which case they can also be called amphibious ), or land animals that have spent at least one life stages (e.g. as eggs or larvae ) in aquatic environments. When referring to plants , the term describes land plants whose roots have adapted well to tolerate regular, prolonged submersion in water, as well as emergent and (occasionally) floating-leaved aquatic plants that are only partially immersed in water. Examples of semi-aquatic animals and plants are given below. Semi aquatic animals include: Semi aquatic plants include: Pelage The fur of mammals has many uses: protection, sensory purposes, waterproofing, and camouflaging, with

5328-502: The water foraging for food. It has a swimming style unique among mammals, propelling itself by alternate strokes of the front feet, while the webbed hind feet are held against the body and only used for steering, along with the tail. It can maintain its relatively low body temperature of about 32   °C (90   °F) while foraging for hours in water below 5   °C (41   °F). Dives normally last around 30 seconds, with an estimated aerobic limit of 40 seconds, with 10 to 20 seconds at

5402-520: Was previously present in its lineage for over 95 million years. Even its closest relative, Obdurodon , which otherwise closely resembles the platypus, retained this tooth row. More recent studies indicate that this tooth loss was a geologically very recent event, occurring only around the Plio - Pleistocene (around 2.5 million years ago), when the rakali , a large semiaquatic rodent , colonized Australia from New Guinea . The platypus, which previously fed on

5476-453: Was thought that somebody had sewn a duck's beak onto the body of a beaver-like animal. Shaw even took a pair of scissors to the dried skin to check for stitches. The common name "platypus" literally means 'flat-foot', deriving from the Greek word platúpous ( πλατύπους ), from platús ( πλατύς 'broad, wide, flat') and poús ( πούς 'foot'). Shaw initially assigned the species

#138861