Graptolithina

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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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