Comparisons with Old World Hipparions
The scatter diagram SD-6 shows that (as far as I know) all Old World Hipparion skulls belong to Group B except H. prostylum (Lubéron LY 592) which has the same proportions as Group A-8 ( Ratio diagram A-8 and H. prostylum).
H. hendeyi (Langebaanweg E 22187), although larger, resembles Cormohipparion B (Xmas 71800 and H. hendeyi).
H. weihohense (AMNH 63702) is not very different from Group B-3 (B-3 and H. weihohense).
H. dietrichi (n=3-14) belongs in Group B-5 (B-5 and H. dietrichi).
H. catalaunicum (Hostalets BM 16397) is very much larger but not too different from Lakotahippus-like Kalobatippus and Protohippus (Lakotahippus-like and H. catalaunicum).
The skulls of H. turkanense, H. primigenium, H. perimense (Old World 1) and of H. moldavicum, H. africanum, as well as the skulls from Maragha (BM 3924) and Piera (10032 and 630) do not resemble any Northamerican skull Group B morph (Old World 2).