Earth Life
Earth Life: Mammalian Skeleton
A very good overview of the structure and function of the mammalian skelton. Includes a nice graphic of an elephant skeleton which serves as a typical (though big) example.
CK-12 Foundation
Ck 12: Biology: Mammal Living and Locomotion
[Free Registration/Login may be required to access all resource tools.] Covers social living and locomotion in mammals.
Earth Life
Earth Life: Locomotion of Mammals
Good site for some general information on the movement of mammals. Gives a description and gives the average speed of a variety of animals.