Crania Generally,
Protomarctus is less robust than the related
Tomarctus in proportions of the
skull. The
nasal sinus of
Protomarctus is multichambered and passes the
frontal-
parietal suture, and is separated by partial
septa on the frontal bone. Unlike later borophagines, the
postorbital process of
Protomarctus is significantly less enlarged, the forehead is less domed and the
palate is more narrow. The
premaxillary process contacts the
nasal process of the frontal bone, and the
nuchal crest is expanded to the point where it surpasses the
occipital condyle.
Protomarctus is also smaller than most other borophagines, though it is around 27% larger than
Microtomarctus. The
molar morphology of
Protomarctus is primitive compared to other borophagines.
Postcrania Postcranial material of
Protomarctus is known, namely
limb bones and
phalanges, though they have yet to be described in detail. == Paleoecology ==