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Graptolithina

Graptolithina (graptolites; phylum Hemichordata) A class of extinct, colonial, marine organisms which secreted a chitinous exoskeleton with characteristic growth bands and lines. The complete skeleton (colony) is referred to as a rhabdo-some. They first appeared in the Middle Cambrian and are last known from the Lower Carboniferous. The class comprises two principal orders: true (graptoloid) graptolites (Graptoloidea), which are important zonal fossils in Ordovician and Silurian rocks; and the dendroid graptolites (Dendroidea).

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

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

Graptolithina

Graptolithina (graptolites; phylum Hemichordata, subphylum Stomochordata) An extinct class of stick-like, colonial, marine organisms that existed from the Middle Cambrian to the Lower Carboniferous. Their fossils are used to establish a stratigraphical time-scale for the Lower Palaeozoic. There were 2 principal orders, Dendroidea and Graptoloidea, and a number of minor, short-lived orders.

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

"Graptolithina." A Dictionary of Earth Sciences. . Encyclopedia.com. (October 20, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/graptolithina

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