The ANIM chunk is always defined in the MESH node which is the parent node for all the joints. You can then nest futher MESH chunks with its own ANIM chunk and its own joint hierarchy.
You could also just parent one animated mesh to a joint in another animated mesh. You would then do a findchild to animate it. This to all intents and purposes is exactly the same.
You could also just parent one animated mesh to a joint in another animated mesh. You would then do a findchild to animate it. This to all intents and purposes is exactly the same.