ABSTRACT
This chapter focuses on the comparative anatomy, evolution, and homologies of the head and neck muscles of the major extant clades of reptiles: Testudines (turtles), Lepidosauria (including Sphenodon, "lizards," mosasaurs, snakes, and amphisbaenians sensuConrad [2008]), Crocodylia (crocodylians), and Aves (birds). It describes the major problems researchers face when they compare the muscles of a certain tetrapod taxon with those of other taxa is the use of different names by different authors to designate the same muscle in the members of different clades and even of the same clade. The intermandibularis is a ventral mandibular muscle that usually connects the two hemimandibles. In numerous lepidosaurs, including Timon, the anlage that gives rise to the intermandibularis becomes differentiated into two separated muscles, the intermandibularis anterior and intermandibularis posterior. The LCA of tetrapods probably had two dorso-medial hyoid muscles, the depressor mandibulae and levator hyoideus, and a ventral hyoid muscle, the interhyoideus.
