Lyne, I had a look at the obj file in UV Mapper_ I don't know whether this will answer your question_but I notice that if you select the tail 'groups' there's an overlapping area which must correspond to the central solid core of the tail. If you select by tail 'material'you loose that area. The overlapping area on the map is in the 'coat' material zone. Prob too simple a solution that but hope it helps!