sphenomandibularis sphenomandibularis the sphenomandibularis is a muscle attaching to the sphenoid bone and the mandible. it is a muscle of mastication. unlike most of the muscles of the human body, which had been categorized several centuries ago, the sphenomandibularis was discovered in the mid-1990s at the university of maryland at baltimore. the findings were published in 1996. the sphenomandibularis is considered by many sources to be a portion of the temporalis, rather than a distinct muscle.