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can you tell which is the largest group of mammals please
The group of mammals has over 5000 species that are found in different sizes and are spread all over the world. This is a diverse group and according to the environment, the individuals of this group have developed different characteristics. While the smallest mammals like shrew and bats weigh as little as 3 grams, on the other hand, the largest mammal on earth, the blue whale, weighs over 160 metric tons. Based on the variety of features that they display, mammals are further divided into the following categories.

Prototheria: Although they are mammals, Prototherians lay eggs. This group includes the platypus and three varieties of the spiny anteaters.
Metatheria: These are mammals that have pouch in which they carry their babies, like the kangaroos. They are also known as the marsupials. Although even marsupials have placenta, it is not as well-developed as it is in placental mammals. Hence, the animal that is born is not completely developed. It completes its development inside its mother's pouch.
Eutheria: These are the placental mammals. A rather diverse group, it includes armadillos, bats, elephants, shrews, whales and of course, human beings. One of the most identifying placental characteristics is that when inside the uterus, the fetus derives nutrition from the mother through the placenta. Unlike marsupials, the placenta plays an important a role in fetal development in the Eutherian mammals.


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