Tentorium cerebelli osseum

The tentorium cerebelli osseum gives attachment, at the fresh state, to the membranous tentorium or tent of the cerebellum (Tentorium cerebelli membranaceum), that moves forward between the cerebrum and the cerebellum. It is very prominent in Carnivorous and a little bit less in Equidae, barely indicated in Ruminants, Pigs and Glires. It results of the unions of several elements:

a) the internal occipital protuberance (Protuberancia occipitalis interna), dorsal and stretched transversally, which belongs to the interparietal bone. It is completed on both sides by the processus tentoricus of the parietal bone and the squamous part of the occipital bone, in variable proportions according to the species;

b) more laterally, the protrusion continues with the cerebro-cerebellar or spheno-occipital crest (Crista sphenooccipitalis). This relief is constant but its constitution varies according to the species;

In Equidae and Carnivorous, it is made of the petrosal crest (Crista partis petrosae), completed by the caudal margin of the squamous part of the temporal bone;

In Ruminants and Porcines, the petrosal crest is missing, and is replaced by a crest of the squamous part of the temporal bone (Crista squamosa).

In Cats, the corresponding crest is formed by the parietal bone. Ventrally, the spheno-occipital crest extends until the apex of the petrous part (Horses, Dogs) or, if not, until the margin of the oval foramen (Ruminants, Pigs).