Toothcomb
- This article is about the tooth structure, for the comb see nit comb.
A toothcomb (tooth comb, dental comb) is an anatomical structure found in strepsirrhine primates, which includes lemurs, lorises and galagos. A toothcomb consists of long, flat forward-angled teeth,[1] and includes the lower incisors and the canine teeth.[2] In indriids, archaeolemurids, palaeopropithecids, the structure consists of four teeth, but it consists of six teeth in all other lemurs except for the highly derived Daubentonia (Aye-aye), which has replaced the toothcomb with a single pair of continuously growing anterior teeth.[3] The first lower premolar following the toothcomb is usually shaped like a typical canine tooth.[2]
Most strepsirrhine species use the toothcomb in grooming, raking it through their fur or the fur of a compatriot. However, there are three known species that use their toothcombs to scrape trees for gum: the Masoala fork-marked lemur,[4] the Verreaux's sifaka,[5] and the Pygmy slow loris.[6]
The first fossil strepsirrhine found to exhibit a toothcomb was Karanisia clarki, an extinct species of loris dating to the Middle Eocene (c. 40 million years ago) and found in Egypt.[3][7] This find, along with the lack of lemur fossils in Madagascar and Africa, has complicated the puzzle of lemur origins and diversification.[3] Adapoids, from which modern strepsirrhines evolved, lacked toothcombs.[8][9][10][11] By the Miocene, toothcombs seem to be the rule among strepsirrhines.[12][13]
There was debate in the past over the cause for the evolution of the strepsirrhine toothcomb. It was argued at one point that the toothcomb evolved as a scraping tool to obtain gum from trees,[14][15] but this idea has been generally discredited and replaced with the idea that it evolved as a grooming tool, just as it is used today.[11][16][17][18][19][20][21][22]
[edit] References
- ^ "New fossils add to primate-origins debate - Fine Toothcomb". Science News. 2003. http://findarticles.com/p/articles/mi_m1200/is_13_163/ai_99849629. Retrieved 2008-08-10.
- ^ a b Macdonald, David (2006). "Primates". The Encyclopedia of Mammals. The Brown Reference Group plc. pp. 292. ISBN 0-681-45659-0.
- ^ a b c Gould, Lisa and Sauther, Michelle L., ed (2006). Lemurs: Ecology and Adaptation (Developments in Primatology: Progress and Prospects) (1 ed.). Springer. pp. 7–8. ISBN 038734585X.
- ^ Petter, J., A. Schilling, and G. Pariente. 1971. Observations éco-éthologiques sur deux lémuriens malgaches nocturnes: Phaner furcifer et Microbus coquereli. Terre Vie 118:287-327
- ^ Richard, A. 1978. Variability in the feeding behavior of a Malagasy prosimian, Propithecus verrauxi: Lemuriformes in G. Montgomery, ed. The ecology of arboreal folivores. Washington, DC, Smithsonian Institution Press
- ^ Tan, C. L., and J. H. Drake. 2001. Evidence of tree gouging and exudate eating in pygmy slow lorises (Nycticebus pygmaeus). Folia Primatologica 72:37-39
- ^ Seiffert, E. R.; Simons, E. L.; and Attia, Y. (2003). "Fossil evidence for an ancient divergence of lorises and galagos". Nature 422 (6930): 421–424. doi:10.1038/nature01489. PMID 12660781.
- ^ Fleagle, J. G. 2000. The century of the past: One hundred years in the study of primate evolution. Evolutionary Anthropology 9:87-100.
- ^ Gingerich, P. D., and R. D. Martin. 1981. Cranial morphology and adaptations in eocene adapidae .2. The Cambridge Skull of Adapis-Parisiensis. American Journal of Physical Anthropology 56:235-257
- ^ Marivaux, L., Y. Chaimanee, P. Tafforeau, and J. J. Jaeger. 2006. New strepsirrhine primate from the late Eocene of Peninsular Thailand (Krabi Basin). American Journal of Physical Anthropology 130:425-434.
- ^ a b Rose, K. D., A. Walker, and L. L. Jacobs. 1981. Function of the mandibular tooth comb in living and extinct mammals. Nature 289:583-585.
- ^ Walker, A. C. 1978. Prosimian primates in V. J. Maglio, and H. B. S. Cooke, eds. Evolution of African Mammals. Cambridge, Massachusetts, Harvard University Press.
- ^ Jacobs, L. L. 1981. Miocene lorisid primates from the Pakistan Siwaliks. Nature 289:585-587.
- ^ Martin, R. D. 1972. Review lecture: adaptive radiation and behaviour of the Malagasy lemurs. Philosophical Transactions of the Royal Society of London B Biological Sciences 264:295-352.
- ^ Martin, R. D. 1990, Primate origins and evolution: a phylogenetic reconstruction. Princeton, New Jersey, Princeton University Press.
- ^ Burrows, A. M., and L. T. Nash. 2009. Galago exudate-acquisition: it's not about the toothcomb. American Journal of Physical Anthropology:99-99
- ^ Burrows, A. M. 2010. Searching for dental signals of exudativory in galagos, Pages 211-233 The evolution of exudativory in primates. New York, Springer.
- ^ Asher, R. J. 1998. Morphological diversity of anatomical strepsirrhinism and the evolution of the lemuriform toothcomb. American Journal of Physical Anthropology 105:355-367.
- ^ Gilmartin, M. 1995. Form and function of the 'toothcomb' of subfossil lemurs: a dental microwear study. American Journal of Physical Anthropology:99.
- ^ Rosenberger, A. L. 2010. Adaptive Profile Versus Adaptive Specialization- Fossils and Gummivory in Early Primate Evolution, Pages 273-295 The evolution of exudativory in primates. New York, Springer.
- ^ Rosenberger, A. L., and E. Strasser. 1985. Toothcomb origins: Support for the Grooming Hypothesis. Primates 26:73-84.
- ^ Szalay, F. S., and D. Seligsohn. 1977. Why did the strepsirhine tooth comb evolve?. Folia Primatologica 27:75-82.
