Sublingua

thumb|upright|right|alt=The underside of the lemur tongue showing the sublingua with its serrated tip|The sublingua is found on the underside of the primary tongue in tarsiers, lemuriform primates, and some other mammals. The sublingua ("under-tongue") is a muscular secondary tongue found below the primary tongue in tarsiers and living strepsirrhine primates, which includes lemurs and lorisoids (collectively called "lemuriforms"). Although it is most fully developed in these primates, similar structures can be found in some other mammals, such as marsupials, treeshrews, and colugos. This "second tongue" lacks taste buds, and in lemuriforms, it is thought to be used to remove hair and other debris from the toothcomb, a specialized dental structure used to comb the fur during oral grooming.

A rigid structure called the plica mediana or lytta runs from the front to the back, down the center of the sublingua to give it support. The plica mediana is usually made of cartilage and attaches the sublingua to the underside of the tongue. In lemuriforms, the sublingua mostly consists of two plicae fimbriatae (singular: plica fimbriata), which run along the sides of the plica mediana and end in comb-like serrated edges that are hardened with keratin. The plicae fimbriatae move freely over a limited range. The plica sublingualis, which is found in all primates, but is particularly small in lemuriforms, attaches the tongue and sublingua to the floor of the mouth. Tarsiers have a large but highly generalized sublingua, but their closest living relatives, monkeys and apes, lack one.