What is a mammals?
Mammals are vertebrates with hair, mammary glands used to suckle young with milk, a diaphragm, three bones in the middle ear, and a lower jaw made up of a single pair of bones that articulates in a unique way with the skull.
Mammals are divided into three groups - monotremes, marsupials and placentals, all of which have fur, produce milk and are warm-blooded.
Placental mammals, like humans, whales, rodents and bats, differ from monotremes and marsupials in that they generally give birth to well-developed young.
Mammals are a diverse group, but all mammals-
- produce milk to feed their young
- have hair or fur
- have a unique jaw structure
- are warm-blooded
Evidence that mammals evolved from reptiles is provided by fossils 250-180 million years old. These fossils include a large number of species that share so many reptilian and mammalian features that they cannot be assigned to either group.
There are 17 orders of terrestrial (land) mammals in Australia.; made up of 4 groups- monotremes, marsupials, rodents and bat. This includes endemic species native to Australia.
All 3 groups of marine mammals, cetaceans, seals and dugongs occur in Australian coastal waters.