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Image Platypus skull

TLF ID R7915

This is a colour photograph of the internal skull of a platypus ('Ornithorhynchus anatinus'). This museum specimen displays two components of the skull: the braincase with fused rostrum and the lower jaw. This image has a pale background and includes a black scale line representing 2 cm. Museum identification labels are attached to the skull. (Classification - Phylum: Chordata, Class: Mammalia, Order: Monotremata, Family: Ornithorhynchidae).

Educational details

Educational value
  • The platypus is one of the two Australian monotremes, the egg-laying mammals. It is common and widespread in eastern Australia from north Queensland to Tasmania, inhabiting freshwater streams, rivers and lakes from the tropical lowland regions to alpine areas. The platypus prefers slow-moving waters lined with steep banks to burrow into for resting by day and to use for nesting and raising young.
  • The platypus is mostly aquatic and has a streamlined body, a broad flat tail and webbed feet. Its soft leathery snout resembles a duck's bill and is a sensory organ used to locate prey. It is carnivorous and feeds upon worms, shrimps, yabbies and insects. Platypuses store food in cheek pouches and process it later on the water surface.
  • The platypus has brown fur on its upper parts and is paler underneath. It has two layers of fur, a thick outer waterproof layer and an inner insulating layer. Platypuses vary considerably in size. The head-and-body length is between 31 cm and 40 cm, its tail is 10-15 cm long, and it weighs between 700 g and 2,400 g, males being larger than females. Males have a venomous spur on the hind foot.
  • Platypus young have three molars, which are later lost, leaving hard pads in the adults. The platypus jaw has a different construction to other mammals and, although they have middle ear bones like other mammals, the external ear opens at the base of the jaw like its ancient ancestors.
  • Monotreme skulls look very different to other mammal skulls, and appear more birdlike. They have an elongate rostrum with a leathery sheath covering, giving it a smooth appearance, and there is an absence of teeth in adults. The brain case of these primitive mammals is small and round.
  • The Australian monotremes consist of just a single species each of platypus and echidna. They have a remarkable reproductive system whereby eggs are laid - two by the platypus and one by the echidna - and the young feed on milk from the mother's milk glands or pores. Monotremes have a lower body temperature than other mammals, and are also characterised by short legs that extend from the body in a similar way to reptiles.
  • The mammal skull is a complex fusion of around 34 bones, in three main parts: the braincase, which encloses the brain, the rostrum including the snout and upper jaw, and the lower jaw or mandible. The mammal skull is distinguishable by the presence of three bones in the middle ear used for hearing (not visible in the image). It also has a unique jaw joint - the single lower jaw bone connects with a small skull bone (the squamosal), resulting in a distinctive jaw movement.
  • There are three types of existing mammals: the placentals, the marsupials, and the primitive monotremes. Placental mammals give birth to live young after extended nourishment from a placenta in the mother's womb, marsupials are characterised by a pouch for rearing the young, and monotremes are egg layers. There are many shared characteristics between these three groups and some important distinctions, especially in the reproductive systems, the skull and dentition.
Year level

6; 7; 8; 9; 10; 11; 12

Learning area
  • science
  • Science/Science understanding

    Other details

    • Content provider
    • Copyright holder
    • Organisation: Museum of Victoria
    • Address: Carlton VIC 3053 Australia
    • Remarks: Reproduced courtesy of Museum Victoria
    • Publisher
    • Date of contribution: 06 Sep 2013
    • Organisation: Education Services Australia
    • Address: Melbourne VIC 3000 Australia
    • URL:
    • Author
    • Name: Marnie Rawlinson
    • Remarks: photographer
    • Author
    • Name: Cathy Accurso
    • Remarks: photographer
    • Author
    • Name: Ken Walker
    • Remarks: photographer
    Access profile
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    Learning resource type
    • Image
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    • © Education Services Australia Ltd and Museum Victoria, 2016, except where indicated under Acknowledgments