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Graptoloidea


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(subphylum Stomochordata, class Graptolithina)

An order of graptolites that existed from the Lower Ordovician to Lower Devonian. The rhabdosomes had up to eight stipes in early forms, but two and finally one in later forms. The thecae are of only one type, equivalent to the autotheca of Dendroidea, occur on one or both sides of the stipe, and vary quite widely in morphology. In adults, there is always a sicula bearing a nema. There are three suborders: one, to which no name has been assigned, comprises a single, paraphyletic family, Anisograptidae. The other two are Dichograptina and Virgellina.

Graptoloidea (saetograptus chimaera)

Subjects: Earth Sciences and Geography.


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