Not so. Just a Neandertal mandible with Neandertal mDNA, but a bit of a mental trigone. I don't think this is demonstrable proof of interbreeding, though of course, I believe interbreeding occurred in general. And the paper certainly does not make the claim attributed to it by Discovery magazine that this is an example of a Neandertal mother and modern human father! I was just hoping for better evidence of interbreeding. I have personally used the chin as a marker of modernity (http://dx.doi.org/10.1016/j.ijpp.2012.06.003), but not necessarily when there is other evidence to the contrary. There are a number of African specimen with mixed archaic and modern features (of course, Loiyangalani!), but I am not aware of other specimens outside the continent with similar mosaics--besides the occasional occipital bun on a modern human, etc. Hopefully further DNA testing can elucidate this specimen's standing; however, at this point, it is still a Neandertal.
On a personal note, I find it increasingly infuriating that not only the popular media, but major players in the field of paleoanthropology, refer to specimens--or others' interpretations of said specimens--as hybrids. NO ONE involved with the Lager Velho child described it as a hybrid, but merely as potentially the product of a population that experience hybridization in the past. I've had to update a number of wikipedia entries on this very subject. And certainly with the data presented, the Mezzena individual was not a hybrid!