Macropodidae

Macropodidae is a family of marsupials, commonly known as kangaroos, wallabies, tree-kangaroos, wallaroos, pademelons, quokkas, and several other terms. These genera are allied to the suborder Macropodiformes, containing other macropods, and are native to the Australian continent, the mainland and Tasmania, and in New Guinea or nearby islands. Although omnivorous kangaroos lived in the past, modern macropods are herbivorous. Some are browsers, but most are grazers and are equipped with appropriately specialised teeth for cropping and grinding up fibrous plants, in particular grasses and sedges. In general, macropods have a broad, straight row of cutting teeth at the front of the mouth, no canine teeth, and a gap before the molars. The molars are large and, unusually, do not appear all at once but a pair at a time at the back of the mouth as the animal ages, eventually becoming worn down by the tough, abrasive grasses and falling out. Like many Macropodiformes, early kangaroos had plagiaulacoids, but these converted into normal molars in more derived species. Most species have four molars and, when the last pair is too worn to be of use, the animals starve to death. The dental formula for macropods is 3.0–1.2.41.000.2.4. Like the eutherian ruminants of the Northern Hemisphere (sheep, cattle, and so on), macropods have specialised digestive systems that use a high concentration of bacteria, protozoans, and fungi in the first chamber of a complex stomach to digest plant material. The details of organisation are quite different, but the end result is somewhat similar. The particular structure-function relationship of the Macropodidae gut and the gut microbiota allows the degradation of lignocellulosic material with a relatively low emission of methane relative to other ruminants. These low emissions are partly explained by the anatomical differences between the macropodid digestive system and that of ruminants, resulting in shorter retention times of particulate digesta within the foregut. This fact might prevent the establishment of methanogenic archaea, which has been found in low levels in tammar wallabies (Macropus eugenii) and eastern grey kangaroo (M. giganteus). Metagenomic analysis revealed that the foregut of tammar wallabies mainly contains bacteria belonging to the phyla Firmicutes, Bacteroides, and Proteobacteria. Among proteobacteria populations of the Succinivibrionaceae family are overrepresented and may contribute to low methane emissions. Macropods vary in size considerably, but most have very large hind legs and long, powerfully muscled tails. The term macropod comes from the Greek for 'large foot' and is appropriate: most have very long, narrow hind feet with a distinctive arrangement of toes. The fourth toe is very large and strong, the fifth toe moderately so; the second and third are fused; and the first toe is usually missing. Their short front legs have five separate digits. Some macropods have seven carpal bones instead of the usual eight in mammals . All have relatively small heads and most have large ears, except for tree-kangaroos, which must move quickly between closely spaced branches. The young are born very small and the pouch opens forward.