Function of the mandibular tooth comb in living and extinct mammals

Abstract

Among the most interesting mammalian dental specializations is the mandibular tooth comb or tooth scraper that evolved independently in certain primates and other mammals. Its occurrence is most widely known in lemurs and lorises, where it is comprised of the long, slender, procumbent incisors (1 or 2 pairs) and incisiform canines. In non-primates the canines are not incorporated into the comb. Some tree shrews (Tupaiidae) possess a tooth comb consisting of the 4 central incisors, and some early Tertiary arctocyonid condylarths had a similar structure composed of all 6 lower incisors. The extant flying lemurs (Dermoptera: Cynocephalus) have a dental comb but it is very different from the ones already mentioned, consisting of 2 pairs of pectinate incisors, each tooth modified into a comb with as many as 15 times. This condition, possibly similar to that in lemurs, is unique to Cynocephalus. One principal function of the tooth comb in primates is to comb the fur; indirect evidence that condylarths used this structure in the same way, millions of years before tooth combs evolved in prosimians, is presented. The comb-like incisors of Cyanocephalus, contrary to popular belief, probably do not function as fur combs.