![]() Living and extinct hyraxes (hyracoids) also exhibit a toothcomb, although the number of tines in the comb vary throughout the fossil record. ![]() Likewise, small- or medium-sized African antelopes, such as the impala ( Aepyceros melampus), have a similar structure sometimes referred to as the "lateral dental grooming apparatus". Toothcombs can also be found in colugos and treeshrews, both close relatives of primates however, the structures are different and these are considered to examples of convergent evolution. An analogous trait is found in the bald uakari ( Cacajao calvus), a type of New World monkey. This homologous structure is a diagnostic character that helps define this clade (related group) of primates. The toothcomb, a special morphological arrangement of teeth in the anterior lower jaw, is best known in extant strepsirrhine primates, which include lemurs and lorisoid primates (collectively known as lemuriforms ). The toothcomb of a colugo differs significantly in shape from that of lemuriform primates. The lack of a distinct toothcomb in the fossil record before to 40 mya has created a conflict with molecular clock studies that suggest an older divergence between lemurs and lorisoids, and the existence of a ghost lineage of lemuriform primates in Africa. Fossil primates such as Djebelemur, 'Anchomomys' milleri, and Plesiopithecus may have been their closest relatives. One popular hypothesis is that they evolved from European adapids, but the fossil record suggests that they evolved from an older lineage that migrated to Africa during the Paleocene (66 to 55 mya) and might have evolved from early cercamoniines from Asia. They are thought to have evolved from early adapiform primates around the Eocene or earlier. In lemuriform primates, the toothcomb has been used by scientists in the interpretation of the evolution of lemurs and their kin. In some lemurs, such as the aye-aye, the toothcomb has been lost completely and replaced with other specialized dentition. Within lemuriforms, fork-marked lemurs and indriids have more robust toothcombs to support these secondary functions. The toothcomb can have other functions, such as food procurement and bark gouging. ![]() The toothcomb is kept clean by either the tongue or, in the case of lemuriforms, the sublingua, a specialized "under-tongue". Fine grooves or striations are usually cut into the teeth during grooming by the hair and may be seen on the sides of the teeth when viewed through a scanning electron microscope. While licking the fur clean, the animal will run the toothcomb through the fur to comb it. The toothcomb is usually used for grooming. The toothcombs of colugos and hyraxes take a different form with the individual incisors being serrated, providing multiple tines per tooth. The toothcombs in most mammals include incisors only, while in lemuriform primates they include incisors and canine teeth that tilt forward at the front of the lower jaw, followed by a canine-shaped first premolar. In most mammals the comb is formed by a group of teeth with fine spaces between them. The structures evolved independently in different types of mammals through convergent evolution and varies both in dental composition and structure. The toothcomb occurs in lemuriform primates (which includes lemurs and lorisoids), treeshrews, colugos, hyraxes, and some African antelopes. The lemuriform toothcomb, viewed from the underside of the lower jawĪ toothcomb (also tooth comb or dental comb) is a dental structure found in some mammals, comprising a group of front teeth arranged in a manner that facilitates grooming, similar to a hair comb.
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