Placental vs Marsupial
Although these terms sound a little unfamiliar, in simple means, placental and marsupial are the common mammalian groups including humans and kangaroos respectively. Therefore, the exhibited differences between these two types are too much to discuss in a small write up like this article. Therefore, the most interesting and important distinctions between these groups are presented in this article. As a very general statement, placental and marsupial animals together contain over 85 percent of all the mammals in the world including the presently most dominant humans.
Placental mammals are the most diversified with the highest number of species among all the three mammalian groups. Humans, elephants, whales, lions, rhinos, and many other are few examples among more than 4,000 placental mammal species. Presently, the most dominant form among terrestrial organisms is the placental mammals. They are warm blooded and have mammalian unique hairs on the skin. Their anal opening and the genitals are separately formed. Placental mammals give birth to live young followed by a gestation period. During the gestation period, the developing foetus being nourished by the mother through the special structure called placenta. In other words, the placenta is the physical medium through which the nutrients are transported into the foetus from the mother’s blood stream. The foetus develops fully and come out as completely developed young or offspring. In addition, the newborns have hairs in placental mammals. Since this placental phenomenon is only present among placental mammals, they bear great importance. Usually, they possess the most developed brains. In addition, the placental mammals mostly dominate the ecological niches.
Marsupials are one of the three major mammalian groups with about almost 500 extant species. Predominantly, the marsupials are found in Australia, and the rest are ranging in South America with very few in North America. Marsupials give birth to an undeveloped young following a small gestation period. The undeveloped young are known as Joey. The Joey comes out of mother, and its development takes place inside an external body pouch that has milk secreting mammary glands. Joeys do not have hairs on their body when they are newly born. In addition, Joeys are tiny as the size of a jellybean, and they cannot open their eyes, or in other words, they are blind. Depending on the species and their relative body sizes, the time inside the mother’s pouch varies, but the completed development has to take place inside the pouch. However, during the short gestation period, there is a placenta between foetus and mother, but it is a very simple structure. One of the noticeable absences in marsupials is the lack of corpus callosum or the bridge of neurons between left and right hemispheres of the brain. Kangaroo, wallaby, and Tasmanian devil are few of the most well known marsupials.
What is the difference between Placental and Marsupial?
• Placental mammals are the most diversified mammals with more than 4,000 extant species in the world, whereas marsupials are less diversified comparatively with about 500 species.
• Placental mammals have a wide range of habitats and distribution over the world, while marsupials are predominantly Australian and some are found in Americas.
• Parentals have a complex and efficient placenta that remains until the completed development of the foetus. However, marsupials have a simple placenta that lasts only for a short period.
• Placental mammals have ossified patellae and corpus collosum, but marsupials do not.
• Placentals are dominant and have a large population, but marsupials have low population.