1- Create a mesh instance for the worm
2- Apply a skeleton behavior to the mesh
3- Create animation range
4- Play it
I saw that the Skeleton behavior belonged to a mesh category (which is why i said that it kinda' didn't make sense during my tests).
The reason for saying this is that the SkeletonCreateAnimRange function needed to access the mesh.skeleton data. A null value was being returned, thus throwing the JS error, meaning that the mesh object (of mesh.skeleton) needed to refer to the root level of the model file as the "skeletons" property resided there.
Strange that the Scene object, which already has the full model data to begin with, couldn't simply be re-used (note that I prefer loading an entire scene with models, anims etc.). The above solution only loads an instance of the worm.js file into a separate OBJ-JS Mesh so as to circumvent the JS error.
Anyway, I'll take that solution (maybe). Many thanks!