Robert Comsol wrote:
Come to think about that, that's probably what they are, "Terran" animal skulls because that would have been cheapest for the actual production. Thus, if we were able to figure out to which animal a certain skull belongs, we would know what these skulls in McCoy's wall shelf actually are and what they should look like...
They don't necessarily have to be from actual Terran animals. They could've been molded out of plaster, etc by the production team.