Mammals have only between 4000 and 5000 known species of mammals that are vertebrates. The largest group would be Osteichthyes (or bony fish) which has an astonishing amount that adds up to roughly...
The blue whale in water, and elephants on land.
the largest vertibrate is the blue whale, Balaenoptera musculus
A vertebrate is an animal that has a back bone (spine).
The emu belongs to the classification of vertebrates known as birds.