Structure of the auditory region of the skull and, particularly, the auditory bulla, bears an extreme significance for the reconstruction of carnivoran phylogeny. In the course of the bulla morphogenesis, its bones (ectotympanic, rostral and caudal entotympanics) undergo diverse transformations determining the definitive bulla architecture. This structure, being complemented by the morphology of the petrosal and other adjacent cranial elements, exhibits the patterns which are relatively stable among the higher-level taxa of Carnivora and, therefore, so important for systematics.

Early students of the carnivoran auditory region (Turner 1848, Flower 1869) paid special attention to the septum bullae, a bone partition dividing the bulla into two chambers. Flower (1869), classifying the major taxa of recent Carnivora, noted its presence in the Felidae, Viverridae, Cryptoproctidae, Protelidae (families belonging to the group Aeluroidea erected by that author) and the Canidae (group