The sphenomandibularis shown on P45 sheet plastination and dissection.

As early as 1955, there were studies on the multiple bellies of the temporalis muscle (TM), which is considered to contain two or three layers. However, some historical literature proposed that the sphenomandibularis (SM), one of the bellies of TM, should be considered a newly discovered independent muscle. Many scholars have extremely inconsistent views on this statement. Here, we conducted an anatomical study to clarify the existence and morphological characteristics of the SM. We dissected 14 formaldehyde-fixed and 6 fresh-frozen human cadaver heads using three approaches, including vascular casting in 10 cases. 15 sets of consecutive P45 sheet‑plastinated sections were analyzed, including 5 coronal, 5 sagittal, and 5 horizontal planes. SM has distinct anatomical features. This strip-like muscle extends from the maxillary surface of the greater wing of the sphenoid bone to the temporal crest behind the retromolar trigone of the mandible. Ours is the first detailed description of SM through combining gross anatomy with the P45 sheet plastination technique. The special anatomical location of this belly may be related to compression of the maxillary nerve, anatomy of the pterygopalatine fossa, identification of the buccal nerve, comprehension of the fascial-tendinous complex, and a deeper understanding of the masticatory system. We recommend the name Sphenomandibularis as a further reference and to distinguish it from TM.