The Paraceratherium a type of hornless Rhino.
I guess the wooly mammoth, which is extinct.
the blue whale, which is the biggest mammal known to man altogether.
Australia
The Red Kangaroo, assuming you're talking about native animals, and animals not extinct.
wooly mammoth
The Thylacine (the correct name for the Tasmanian tiger) was a marsupial mammal: therefore, it was a vertebrate.
The Hippopotamus is the 3rd largest mammal.
The largest mammal in the world is the blue whale. They have been known to be over 100 feet long and to weigh as much as 200 tons. They are not only the largest living animals, they are the largest animal that is known to have ever existed.
There is no such thing. No bird is or ever was a mammal.
The oldest extinct mammal is one that lived among the dinosaurs. There are new mammals that are being discovered regularly.
By almost any absolute measurement, the blue whale is the biggest mammal living today. It can grow up to 100 feet and weigh more than 100 tons. On land its the African elephant.
The blue whale is the largest mammal on earth.