page_title: Platypus
section_title: Description
hierarchical_section_title: Platypus / Description
caption_attribution_description: Ornithorhynchus anatinus Deutsch: de:Schnabeltier im de:Eungella-Nationalpark, de:Queensland
context_page_description: The platypus, 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 of its family and genus, though a number of related species appear in the fossil record.
  Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young. Like other monotremes, it senses prey through electrolocation. It is one of the few species of venomous mammals, as the male platypus has a spur on the hind foot that delivers a venom capable of causing severe pain to humans. The unusual appearance of this egg-laying, duck-billed, beaver-tailed, otter-footed mammal baffled European naturalists when they first encountered it, and 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 an important subject in the study of evolutionary biology, and a recognisable and iconic symbol of Australia.
context_section_description: In David Collins's account of the new colony 1788–1801, he describes coming across "an amphibious animal, of the mole species". His account includes a drawing of the animal.
  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 fur is waterproof, and the texture is akin to that of a mole. The platypus uses its tail for storage of fat reserves (an adaptation also found in animals such as the Tasmanian devil). The webbing on the feet is more significant on the front feet and is folded back when walking on land. The elongated snout and lower jaw are covered in soft skin, forming the bill. 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 0.7 to 2.4 kg (1 lb 9 oz to 5 lb 5 oz), with males being larger than females. Males average 50 cm (20 in) in total length, while females average 43 cm (17 in), with substantial variation in average size from one region to another. This pattern does not seem to follow any particular climatic rule and may be due to other environmental factors, such as predation and human encroachment.
  The platypus 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.
  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 have heavily keratinised pads in their place. The first upper and third lower cheek teeth of platypus nestlings are small, each having one principal cusp, while the other teeth have two main cusps. The platypus jaw is constructed differently from that of other mammals, and the jaw-opening muscle is different. As in all true mammals, the tiny bones that conduct sound in the middle ear are fully incorporated into the skull, rather than lying in the jaw as in cynodonts and other pre mammalian synapsids. However, the external opening of the ear still lies at the base of the jaw. The platypus has extra bones in the shoulder girdle, including an interclavicle, which is not found in other mammals. As in many other aquatic and semiaquatic vertebrates, the bones show osteosclerosis, increasing their density to provide ballast. It has a reptilian gait, with the legs on the sides of the body, rather than underneath. When on land, it engages in knuckle-walking on its front feet, to protect the webbing between the toes.
caption: Platypus in Broken River, Queensland
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