Comparative anatomy of the hyoid apparatus of carnivores

The hyoid apparatus was described in order to examine morphological differences among eight species of carnivores. Confusion in terminology of its proximal elements is corrected at first. The tympanohyal, attached to the petrosal part of the temporal bone, is a small bone inside the stylomastoid foramen in the red fox, raccoon dog (Canidae), Asiatic black bear (Ursidae), and masked palm civet (Viverridae), in contrast, it is not visible in the Japanese weasel, Siberian weasel, Japanese marten (Mustelidae) and raccoon (Procyonidae). Inter-specific structural differences of the remainder of the hyoidean elements are not distinct. The basihyal attaches to the ceratohyal and thyrohyal. The thyrohyal is also connected with the thyroid cartilage. The anterior cornu besides the tympanohyal comprises, from distal, three bones; the ceratohyal, epihyal, and stylohyal, and a band of cartilage. The tympanohyal, if present, is connected to the stylohyal via the tympano-styloid synchondrosis. Allometry between the length of the hyoidean elements and that of the skull shows isometric growth. This reflects simply the masticatory function of the hyoid apparatus. The tympanohyal of the mustelids and procyonid is possibly covered and hidden by the tympanic bulla.