> This is an interesting problem: should you err on the side of creating new species every time you find a bone fragment or should you assume it is more of the same?

That is an extant fight in taxonomy, and one which has been going on for more than a century and a half: http://en.wikipedia.org/wiki/Lumpers_and_splitters

> splitters make very small units – their critics say that if they can tell two animals apart, they place them in different genera … and if they cannot tell them apart, they place them in different species. … Lumpers make large units – their critics say that if a carnivore is neither a dog nor a bear, they call it a cat.