The type skull (Wehrli 1941, pl.17-fig.4) belongs to the Münster collections (Inv.-Nr I/7). The exact origin of the skull is unknown. The measurements were taken on the cast at the AMNH (n° SI/7). The specimen lacks the cranial part but the face is well preserved. The preorbital fossa (POB) is weak, situated at 42mm from the orbit. The muzzle is short, wide, with a marked constriction.
I have not observed any skull with exactly the same proportions as the type, but a dozen probably belong to the same group if not to the same species ; all possess short, wide muzzles with strong constrictions ; they differ mainly by the depth of the narial opening. If its deepening is an evolutive character (Eisenmann 1981, 1982) the specimen from Q6 (AMNH 22990) is the most primitive and the specimen of Darmstadt (no information on the quarry) – the most evolved. AMNH 22860 from Q4 is a large cranium with a POF situated at 43mm from the orbit and relatively small teeth. The depth of the narial opening is intermediate between what is seen on the type cranium and crania from Q1. Both Sondaar and Forstén refer it tentatively to the H. dietrichi group. But this specimen differs by a longer Vomer-Basion distanace, a relatively long muzzle without constriction, and by a larger frontal width. The last peculiarities could be artefacts related to fosilization but no crushing could have changed the relative lengths of palate and muzzle. Moreover, similar proportions may be found on other crania from Samos. Fragmentary AMNH 20692 seems to have relatively a deeper narial opening than other H. dietrichi crania from Q1 and relatively small teeth. Juvenile AMNH 20661, also from Q1, has a relatively long muzzle.
On the whole, however, the H. dietrichi group is rather homogeneous.