H. proboscideum group

H. proboscideum group.

The type cranium (Studer 1911, fig.1) belongs to the Bern Naturhistorichen Museum (Nr 46). The exact origin is unknown. The specimen lacks the cranial part but the face is well preserved.
The size is about that of Equus hemionus. The cranium is characterized by a very deep narial opening. There are two preorbital fossae (POF), the posterior one is situated close to the orbit (at 18mm). The muzzle is long and naroow.

Another specimen, also of unknown locality, is very similar but noticeably larger; it is the Münster SI/4, figured by Wehrli; a cast of it is at the American Museum. This cranium bears also two POF, the posterior one at 17mm from the orbit.

Specimens resembling most the ones above are AMNH 20771 and 20772, found in Quarry X (Samos I in Forsten). Both are medium-sized. AMNH 20772 has a very deep narial opening, two POF and a longer muzzle. In both crania, the posterior POF are close to the orbit (28-30mm) although not as close as in the type (whether an anterior POF was present on (fragmentary) AMNHN 20771 is unknown).

AT Q1, the fragmentary AMNH 20594 and 20635 probably belong to the same group. Both are larger than the type. What is preserved of the cheek in AMNH 20594 shows that the POF was very close to the orbit (19mm).

The status of AMNH 22838 from Q4 is problematic. This large cranium has roughly the proportions of H. proboscideum (long muzzle, deep narial opening) but there is just one single POF, far from the orbit (47mm). The cranium from Genève 825-1-1 looks similar.

In short, the material referrable to H. proboscideum is not homogeneous : size, relative length of the muzzle, degree of muzzle constriction, number and situation of the POF vary very much.