[Criteria of the homology and phylogeny of facial muscles in primates including man. I. Prosimia and Platyrrhina].

The facial muscles of primates are derivates of sphincter colli profundus muscle and platysma myoides. A third superficial muscle layer which is present in primitive mammals is found as a rest in Tupaiiformes. The facial muscles of some Lemuriformes must be considered as a model from which originate the facial musculature of other primates. The new formation of muscles takes place at the margine of the original muscle layers; marginal muscle fibers assume another run and get individualized. So it can be seen in facial muscles of prosimians and platyrrhine monkeys that the profound muscles of mouth and nose and some of the rostral margine of the auricle have orginated from sphincter colli muscle, all others from platysma myoides. Primitive and modified muscle forms and intermediate muscle forms can be observed among prosimians as well as among platyrrhine monkeys and by this it is possible to see the homology of the facial muscles.