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Which mammal group has the greatest number of species?
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mammal
Mother polar bear nursing her cubs (Ursus maritimus).
The group of mammals with the greatest number of species is the order Rodentia (rodents).123
Rodents are the most numerous of all existing mammals, both in terms of the total number of species and the total number of individuals. They constitute nearly half of all known mammalian species, with estimates of nearly 2,300 species organized into 30 families. This diverse order includes familiar animals such as rats, mice, squirrels, beavers, and porcupines.312