Sciuridae

Abstract

The skull in sciurids is high and broad. All sciurines and petauristines except the Chadronian? Protosciurus jeffersoni have a sciuromorphous zygomasse-teric structure with the infraorbital foramen small, laterally compressed, and low on the rostrum with a bony flange extending lateral and ventral to it (Fig. 11.1). The zygoma of ?Protosciurus jeffersoni is protrogomorphous with a primitive infraorbital foramen. The Cedromurinae have a modified protrogomorphous zygoma, in which the ventral surface of the anterior root of the zygoma is broader than in other protrogomorphous rodents and is clearly tilted anterodorsally which has caused some lateral compression of the infraorbital foramen. Korth and Emry (1991) have suggested that this might be a modified myomorphy with the possibility of invasion of the infraorbital foramen by the masseter.