This is a fairly common problem in taxonomy, where to draw the line between species and subspecies. That is why you will occasionally see mention of "lumpers"

This is a fairly common problem in taxonomy, where to draw the line between species and subspecies. That is why you will occasionally see mention of "lumpers" and "splitters", those who include everything possible into one species, and those who break things up into multiple species rather than subspecies. (Lumpers and splitters also occur at higher levels of organization - genera, families, and even orders - in some classes and phyla.) Of course, in paleontology you also have the problem of different aged animals looking different and single oddities getting written up as species because of the extremely small sample size available.