Primate anatomy

The philtrum (, from Ancient Greek , lit. 'love charm') or medial cleft is a vertical indentation in the middle area of the upper lip, common to therian mammals, extending in humans from the nasal septum to the tubercle of the upper lip. Together with a glandular rhinarium and slit-like nostrils, it is believed to constitute the primitive condition for at least therian mammals. Monotremes lack a philtrum, though this could be due to the specialised, beak-like jaws in living species.

bony ridge located above the eye sockets of all primates

thumb|The Lemuriformes|lemuriform toothcomb, viewed from the underside of the lower jaw

claw or nail on the foot of certain primates, used for personal grooming

fold separating the thigh from the buttock

straight or arched rod of bone that forms the posterior rim of the eye opening (orbit) in amniote skulls

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 "seco