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placoid scale

A Dictionary of Zoology | 1999 | | Copyright

placoid scale (dermal centicle) A type of scale that comprises the basic unit of the hard skin cover of sharks. It consists of a hard base embedded in the skin and a spiny process (cusp); these are covered by vitrodentine. The scale projects outwards and backwards and it is the cusps that are responsible for the roughness of the shark's skin. The bulk of the scale consists of dentine surrounding a central pulp cavity. Unlike the scales of bony fish, placoid scales stop growing after they reach a certain size and new scales are added as the animal grows.

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MICHAEL ALLABY. "placoid scale." A Dictionary of Zoology. 1999. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>.

MICHAEL ALLABY. "placoid scale." A Dictionary of Zoology. 1999. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O8-placoidscale.html

MICHAEL ALLABY. "placoid scale." A Dictionary of Zoology. 1999. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O8-placoidscale.html

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placoid scale

A Dictionary of Earth Sciences | 1999 | | Copyright

placoid scale (dermal denticle) Type of scale that comprises the basic unit of the hard skin cover of sharks. It consists of a hard base embedded in the skin and a spiny process (cusp); these are covered by a hard, enamel-like substance (vitrodentine), and the scale projects outwards and backwards. The bulk of the denticle consists of dentine surrounding a central pulp cavity. Unlike the scales of bony fish, placoid scales stop growing after they reach a certain size and new denticles are added instead.

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AILSA ALLABY and MICHAEL ALLABY. "placoid scale." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "placoid scale." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O13-placoidscale.html

AILSA ALLABY and MICHAEL ALLABY. "placoid scale." A Dictionary of Earth Sciences. 1999. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-placoidscale.html

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placoid scale

A Dictionary of Biology | 2004 | Copyright

placoid scale (denticle) See scales.

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"placoid scale." A Dictionary of Biology. 2004. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>.

"placoid scale." A Dictionary of Biology. 2004. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O6-placoidscale.html

"placoid scale." A Dictionary of Biology. 2004. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-placoidscale.html

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Free newspaper and magazine articles

	Caudal spine replacement and histogenesis in the round stingray, Urobatis... Magazine article from: Bulletin (Southern California Academy of Sciences); 12/1/2004
	Sharks: Dangerous or Endangered? Magazine article from: The World and I; 1/1/2004
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