In other mammals, the cloaca is divided into an anus and genitourinary passages. Monotremes, like all reptiles, also have a cloaca, a single opening through which feces, urine, and sperm or eggs pass. In monotremes, the eggs are fertilized internally, but are incubated and hatched outside the body. In other mammals, the young are conceived within the female ’s body and are born alive. For example, monotremes are the only egg-laying mammals. All three species in the order Monotremata are considered primitive, combining mammalian features with those of lower orders of vertebrates such as reptiles. There is only one species of platypus, Ornithorhynchus anatinus, which is comprised of four subspecies. The families are Tachyglossidae (the spiny anteaters or echidnas) and Ornithorhynchidae (the platypus). The platypus is classified in the order Monotremata (meaning single hole), consisting of two families and three genera. The rest of its time is spent in burrows, which it digs in the river banks. Commonly referred to as the duck-billed platypus, it spends several hours each day in the creeks and rivers of eastern Australia and Tasmania. The platypus measures around 17.7 in (45 cm) in length, with its tail adding an additional 5.9 in (15 cm). Its eyes are very small, and it does not have external ears. While the fur on its back is dense, bristly, and reddish or blackish brown, the fur on its underbelly is soft and gray. It also has short, powerful legs and webbed feet. Physically, it looks like a mole or otter, with a beaver ’s flattened tail and a duck ’s bill. The platypus is an egg laying mammal that is well adapted to the water.

Platypus pictures