I am trying to create a mecanim with my character. The problem is my character has no legs. Is it possible to still create a mecanim with the missing parts of the body?
Yes you can, but not as a Human type Mecanim animation rig. You must instead use a Generic type Mecanim animation rig.
Also note that there’s no such thing as “a Mecanim”; Mecanim is the name of the animation system used in Unity, not the name of an animation rig you can create inside Unity.
Read the manual on the Mecanim Animation System for more information.