Cephalic morphology of the honey possum, Tarsipes rostratus (Marsupialia: Tarsipedidae); an obligate nectarivore.

The sharply tapering skull of the honey possum is delicately constructed and has only a few, minute teeth; its mandible is reduced to a thin, flexible rod. The mandibular fossa has been displaced caudally to the caudomedial corner of the squamosal. Head skeletons of the feathertail glider and western pygmy-possum, omnivores that are closely related to the honey possum, bear greater resemblance to the distantly related carnivorous fat-tailed dunnart than to the honey possum. Selected muscles associated with the jaws, hyoid, and tongue of these four mouse-sized (9-22 g) marsupials are described for the first time. The honey possum is characterized by a greatly reduced temporalis that is almost completely hidden by the eye. Its digastric consists of a single belly that inserts onto the caudal margin of the mylohyoid. The lateral pterygoid is relatively long as it extends caudally to insert onto the elongated mandible. The stylohyoid originates high up on the caudal surface of the tympanic bulla; it curves around the caudal and ventral surfaces of the bulla to reach the basihyoid. The insertion of the genioglossus is restricted to the caudal quarter of the tongue. Homologous muscles of the feathertail glider and western pygmy-possum are more similar to those of the fat-tailed dunnart. In addition to the very different musculoskeletal system, the honey possum has an unusual tongue that tapers to a fine point.