This is what we call a skeleton. The basic plan of the mammalian skeleton, as seen above, is fairly straight forward. It consists of a head at one end of a vertebral column from which extend ribs to support the working organs and four limbs for locomotion. The vertebral column ends in a tail. The huge range of lifestyles and habitats utilised by mammals means that a great deal of variety exists between different groups.
Some species lack a tail, others lack apparent hind limbs and the skull is very variable.
Here I am going to give you a general outline of the mammalian skeleton with some notes to indicate particular variations. To understand the skeleton fully you should also have a look at the page on Bones and Joints . The vertebrate skull in general and the mammal skull in particular is a complex amalgam of bones, not just one or two but about 34 bones, if they all are present, make up the skull and lower jaw. Most of these bones are now fused together though anyone who has looked carefully at a mammal skull will have notices the crinkly lines where the once individual bones meet. Most of them come in pairs, one each side.