User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-184.38.5.102-20130105203558/@comment-2194133-20130108022214

I personally think that those are Lao Shan Lung bones or the monster they belong to is somewhat related or similar to it.

Also, if Lao Shan Lung IS back then they could make the battle like Shadow of the Colossus, with all the climbing on the back type thing. It would make sense since climbing has become one of the gimmick gameplay enhancements of MH4 and Lao Shan Lung was the first "ride on the back" type monster introduced to the series (others being Yamatsukami, Jhen Mohran, Shen Gaoren..etc.) although in a very basic manner.

However, the bones in the Primeval Forest are very large. Maybe too large to be Lao Shan bones, unless its purpose is to back the theory that the previous Lao Shans that we have been figting  are in fact juveniles or infants. Only time can tell.