As we mentioned briefly in Chapter 1, The Zombie Attacks!, there are certain requirements that we need to consider if we want to create a rigged character that is fully compatible with Mecanim's tools. In order to make use of the Humanoid Avatar preset in Mecanim, we need a minimum of 15 bones, typically:
Hips or root joint
The skeletons that we will create in 3ds Max and Maya will have quite a few more bones than these—supporting full hand articulation, but this is not strictly necessary to make use of the animation and retargeting tools that Mecanim offers.
Your bones do not have to be named this way, though it is a good idea to adopt consistent naming conventions between your characters. The Avatar in Mecanim acts as an intermediary between the animation and the skeleton, which helps when retargeting animations between different characters.
Mecanim has support for hands, fingers...