Hi RAB,

  Mammal is the name for a large group of animals. They have vertebrates, which mean they have back bones and unlike reptiles and amphibians, they are warm blooded. Mammals can also be recognised by their fur or hair, and by the fact that they feed their babies milk. They are highly adaptable, which means they can live forests, oceans, polar regions and deserts. The polar bear and the grizzly bear are also mammals.  So, surprise! surprise! even a polar bear can stand upright, just like a human. Here is a snap of the same. Here is a link related to the skeletal system. Bye!

https://en.wikipedia.org/wiki/Human_skeleton.