The class methatheria is made up of marsupials these marsupials have the placenta get their nourishment from yolk. Their young is altricial meaning that they are incapable of moving around on their own soon after bring born. They have a short gestation and a long lacatopn period for their young. A good way to differentiate them from eutherians is by looking at their premolars and molars. Metatherians have three premolars and 4 molars. Eutherians were found as early as the cretaceous for their fossils they have a chorioallantoic placenta. As for their prmolars and molars they have 4 premolars and three molars. Eutherians have more morphological diversity compared to the metatherians. They have a greater range in body size, more complex social behavior, and precocial young. This means their young is pretty well developed to survive outside the womb. They also have higher taxanomic diversity, relatively bigger brains, and higher metabollic rates. They also have a higher investment in gestation instead of lactation. Which means there is faster postnatal growth.
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