To help with its semi-aquatic lifestyle, the platypus has webbed feet and a broad, flat tail that acts as a rudder.
The platypus is very reliant on this for catching food it even closes its eyes underwater. Soft and pliable, the bill amazingly has electroreceptors, enabling it to sense electrical fields generated by muscle contractions. Although its “bill” looks like a duck’s, it is very different the bill actually helps it sense prey. Swimming around in the freshwaters of Australia and Tasmania, the semi-aquatic platypus hunts small invertebrates, fish, and amphibians. The duck-billed platypus, as might be expected of an animal that looks like a cross between a duck and a beaver, is very well adapted to life in the water. At least two other monotremes families have been deciphered from fossils, but they are now extinct, along with many genera. The echidna family ( Tachyglossidae) has four existing species, including three endangered long-beaked echidna species and one short-beaked species. The duck-billed platypus ( Ornithorhynchus anatinus) is the only living member of its family ( Ornithorhynchidae). Today, only five species of monotremes exist, three of which are critically endangered. Of particular note, all monotremes have several distinct skull features in common: high-domed craniums, dental similarities including a lack of teeth in adults, and elongated rostrums, or “snouts.” Overall, this leads to monotremes having heads with a rather bird-like appearance. They have a lower body temperature than most mammals (around 90 degrees Fahrenheit), several reptilian bone features, chromosome compilations suggesting greater reptilian influence, and sperm and testes structures that are similar to reptiles’. Additionally, like marsupials, echidnas have a pouch for their young.Īside from the clearly reptilian traits of laying eggs and having a cloaca, monotremes share many other more subtle reptilian traits as well.
Certain brain features and the act of “premature” birthing are shared between monotremes and marsupials. They appear to have more in common with marsupials than placental mammals. Monotremes should not be thought of as precursors to the other mammalian groups, but a branch that diverged from the others at an earlier point in history. Their geographic isolation from placental mammals on Australia may have allowed them to survive there. They have since gone extinct everywhere except Australia and some nearby islands. Marsupials and placental mammals are much more similar to each other they shared common ancestors until 90 million to 65 million years ago.īecause few species of monotremes exist anymore, their evolutionary past is difficult to decipher, but it is thought that monotremes originally evolved in Australia and spread to South America and Antarctica, which were all connected at the time. Monotremes have retained and modified these and other reptilian traits from the Jurassic period, 200 million to 145 million years ago, which is when they diverged evolutionarily from all other mammals. Also like birds and reptiles, monotremes lay eggs, although their eggs are uniquely rubbery and rather small. The word “monotreme” literally means “one opening,” which is a characteristic feature: similar to birds and reptiles, they have the same opening for fecal matter, urine, and reproduction, called a cloaca. The order shares several obvious characteristics with reptiles and birds, making them quite different from both placental mammals (like us) and marsupials ( which were talked about previously).
Only two families of monotremes are still around today: the duck-billed platypus and the echidnas. Because it has a bill like a duck, lays eggs like a bird, has poisoned spurs, and swims around in the water with webbed feet and a paddle-like tail, it’s often called “God’s joke.” The platypus is just one of the remaining species belonging to a most astonishing order of mammals: the monotremes. The duck-billed platypus is quite the strange mammal. This short-beaked echidna (Tachyglossus aculeatus) is a member of one of two families that currently make up the strangest group of mammals alive, the monotremes.
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