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. 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.Įchidnas “trailing” one another in Taronga Zoo. 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. 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. 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). Monotreme means “single hole”, referring to the multi-purpose opening in their rear end used for both excretion and reproduction. Long-beaked echidna ( Zaglossus bruijni). Like our ancient reptilian cousins, they lay eggs. 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. 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. Like the marsupials and the largest mammal group alive today, the placental mammals, the monotremes are furry, warm-blooded, and produce milk. They are the only representatives of this group left, surviving among the marsupials of Australia, Tasmania and New Guinea. The platypus and its closest relative, the echidna, belong to an order of mammals called the monotremes (Monotremata). 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? Their strangeness is more than skin deep.
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