Yeah, it really made me wonder. It must be an intentional design decision. The only other possible explanation is that this is test footage (can we do a lion fight well?) and the environment was some sort of stock cave-with-bones scene, only there weren't any stock cave-with-elephant-bones scenes in the stock CGI library they use.And I really have a bit of a WTF over those bones in the trailer.
If they are incorporating human bones intentionally, there's probably some human element in the story in this version.