Kangaroos are widely distributed in Australia, Tasmania, New Guinea and their neighboring islands, belonging to the possent suborder Possum of the mammalian order. The most significant feature of marsupials is that their pups are born at immature due to the lack of placenta, which is a "premature baby" and needs to continue to develop in the mother's pocket. There are many species in the order Kangaroo, suborder Kangaroos, suborder Wombats, and possums. Not all hatchling bags are located like kangaroos on the abdomen, with the opening upwards. For example, tasmanian bags, tasmanian devils, wombats, the nursery bags are closer to the butt, and the opening is downward.
There are three main classes of mammals, namely single-porous, marsupial and placental. Single-porous animals include the familiar platypus, echidna, etc., whose urinary, reproductive and digestive are achieved through the only "cloaca"; the biggest feature of marsupials is that the female has a nursery bag in the abdomen, the larvae are born very immature, and must breastfeed in the mother's brood bag for a long time, including kangaroos, wombats and possums, etc.; and the biggest feature of placental animals is that the female has a placenta, and the larvae can absorb nutrients through the placenta in the mother's womb and be born after maturity.
Marsupials and placenta, which account for as many as 99% of existing mammal species, originate and when they differ have greatly influenced the pattern of modern Earth's ecosystems and are key scientific questions in mammalian evolutionary research.
wombat
Marsupials are closer to placentals in some important ways. Such as body coat, a single mandible, mammary glands, fetal birth, etc.; but some aspects are still at a more primitive level, such as the cloaca, there is no real placenta. There are remnants of the black beak bone on the shoulder strap, and the upper pubic bone on the belt. The distinguishing characteristics of marsupial skulls are: the mandibular horn process is curved inward, the posterior part of the nasal bone is wide, the anterior jawbone never contacts the frontal bone, the cheekbones extend backwards to form part of the jaw joint fossa, and the posterior edge of the palate bone is thicker.
The thylacine is extinct
According to fossil data, marsupials originated as a suborder of The Cretaceous protozoa in North America, and by the Late Cretaceous had become an important component of the North American fauna. They were all small mammals belonging to the opossum family, one of which (valgyvas) spread to Europe, where it multiplied until the Miocene. Marsupials flourished throughout the Tertiary Period, and only became extinct rapidly after the Pliocene Panama Land Bridge connected South and North America and placentals were invaded by North America. Living marsupials are descendants of possum-like ancestors of the Late Cretaceous who came to Oceania via Antarctica from South America.
opossum
Among the extant marsupials, possum and neokangaroos are distributed in South and North America, while the remaining families are distributed in Oceania. Oceania's marsupials occupy the equivalent of all the ecological niches occupied by placenta on other continents: herbivorous, insecticious, carnivorous and omnivorous, running, jumping and even gliding, ground-dwelling, arboreal and underground living species. The thylacine, tasmanian, tasmanian, possum, wombat, possum, etc. in marsupials can all be found in placenta with very similar species.
This article is the original of the Encyclopedia of China database, and its reproduction must be authorized.