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pygidium

pygidium (adj. pygidial) The posterior part of the exoskeleton of a trilobite (Trilobita); it is generally formed by the fusion of several body segments but in some Cambrian forms consisting of a single segment. Many Cambrian trilobites have small pygidia and are said to be ‘micropygous’. Most trilobites are either isopygous, where the cephalon and pygidium are the same size, or heteropygous, where the pygidium is the smaller. In some cases the pygidium is larger than the head (macropygous).

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"pygidium." A Dictionary of Earth Sciences. . Encyclopedia.com. 20 Aug. 2017 <http://www.encyclopedia.com>.

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"pygidium." A Dictionary of Earth Sciences. . Retrieved August 20, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pygidium

pygidium

pygidium The terminal segment of an insect; the sclerites which surround the anus. See also CERAPACHYINAE.

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"pygidium." A Dictionary of Zoology. . Encyclopedia.com. 20 Aug. 2017 <http://www.encyclopedia.com>.

"pygidium." A Dictionary of Zoology. . Encyclopedia.com. (August 20, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pygidium-0

"pygidium." A Dictionary of Zoology. . Retrieved August 20, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/pygidium-0