Tooth: Difference between revisions

'''Monophyodonts'''<!-- "Monophyodont" redirects here, hence bolded as per [[MOS:BOLD]] --> are animals that develop only one set of teeth, while [[diphyodont]]s grow an early set of [[deciduous teeth]] and a later set of [[permanent teeth|permanent or "adult" teeth]]. [[Polyphyodont]]s grow many sets of teeth. For example, [[shark]]s, grow a new set of teeth every two weeks to replace worn teeth. Most extant mammals including humans are diphyodonts, but there are exceptions including elephants, kangaroos, and manatees, all of which are polyphyodonts.

 

 

Teeth are not always attached to the jaw, as they are in mammals. In many [[reptile]]s and fish, teeth are attached to the [[palate]] or to the floor of the mouth, forming additional rows inside those on the jaws proper. Some [[teleost]]s even have teeth in the [[pharynx]]. While not true teeth in the usual sense, the [[dermal denticle]]s of sharks are almost identical in structure and are likely to have the same evolutionary origin. Indeed, teeth appear to have first evolved in sharks, and are not found in the more primitive [[jawless fish]] – while [[lamprey]]s do have tooth-like structures on the tongue, these are in fact, composed of [[keratin]], not of dentine or enamel, and bear no relationship to true teeth.<ref name=VB/> Though "modern" teeth-like structures with [[dentine]] and [[tooth enamel|enamel]] have been found in late [[conodont]]s, they are now supposed to have evolved independently of later vertebrates' teeth.<ref>{{cite journal|last=McCOLLUM|first=MELANIE|author2=SHARPE, PAUL T. |title=Evolution and development of teeth|journal=Journal of Anatomy|date=July 2001|volume=199|issue=1–2|pages=153–159|doi=10.1046/j.1469-7580.2001.19910153.x|pmid=11523817|pmc=1594990}}</ref><ref name=":3">[http://www.nature.com/news/fossil-scans-reveal-origins-of-teeth-1.13964 nature.com, ''Fossil scans reveal origins of teeth'', 16 October 2013]</ref>