There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
From Merriam and Stock (1932) and Marciszak et al. (2014).
P. fossilis has a narrow occipital protuberance compared to the other two, similarly to the island tigers as compared to their mainland relatives. P. fossilis also looks to have more continuous triangular cranium. These two traits do not really vary intraspecifically and thus are notable interspecific discrepancies. In terms of shape, I find P. atrox and P. spelaea close to each other with P. fossilis a very unique form. Observations like this make it very difficult to figure out which species is closer to which.