I found the above linked video looking for size comparisons of African antelope but this 16 minute video (U-Tube so beware the profit making interruptions) covers all species alive and extinct (easy to tell the difference for extinct because of color name in read versus green for extant species). Fascinating to see the size difference from the tiniest I'd never heard of before to the largest. It also provides a good guide to coloration differences and morphological differences. There is a human figure in silhouette through the whole video to aide in size comparison.
Thought for those who are painting African animals (most of the species are in Africa - but you'll have to verify, video doesn't specify geographic location), you'd find this of interest.
One idea I did think of while watching is finding suitable animals in other scales to increase the paintable options. For me, if I can find some 20 mm animals, I can likely paint them as larger species. Will also chase 10 mm animals for the same reason. Same might work in reverse for finding smaller scales for the smaller animals in larger scales. For the moment, in 15 mm the only animal I know of is Irregular's American Pronghorn antelope - but it can be adapted with paint to some African species with a little imagination (and it has at least a couple of variations). Hopeful that there will be other options soon.
Enjoy.