We don't have synonyms for mentalis yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are mental, mentality and mentalism.
(n) :
(anatomy) A paired central muscle of the lower lip, situated at the tip of the chin; it originates in the incisive fossa of the mandible, inserts in the skin of the chin, and raises the chin and pushes up the lower lip.
(n) :
(anatomy) A paired central muscle of the lower lip, situated at the tip of the chin; it originates in the incisive fossa of the mandible, inserts in the skin of the chin, and raises the chin and pushes up the lower lip.