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Graptolithina is a class in the animal phylum Hemichordata, the members of which are known as graptolites. Graptolites are fossil colonial animals known chiefly from the Upper Cambrian through the Lower Carboniferous (Mississippian). A possible early graptolite, ''Chaunograptus'', is known from the Middle Cambrian. The name graptolite comes from the Greek ''graptos'', meaning "written", and ''lithos'', meaning "rock", as many graptolite fossils resemble hieroglyphs written on the rock. Linnaeus originally regarded them as 'pictures resembling fossils' rather than true fossils, though later workers supposed them to be related to the hydrozoans. More recent work places them near the pterobranchs, possibly within. One analysis suggests that the Pterobranchia represent extant graptolites. ==Taxonomy== The name "graptolite" originates from the genus ''Graptolithus'', which was used by Linnaeus in 1735 for inorganic mineralizations and crustations which resembled actual fossils. In 1768, in the 12th volume of Systema Naturae, he included ''G. sagittarius'' and ''G. scalaris'', respectively a possible plant fossil and a possible graptolite. In his 1751 ''Skånska Resa'', he included a figure of a "fossil or graptolite of a strange kind" currently thought to be a type of ''Climacograptus'' (a genus of biserial graptolites). Later workers used the name to refer to a specific group of organisms. ''Graptolithus'' was officially abandoned in 1954 by the ICZN, partly because of its original purpose as a grouping for inorganic mimicries of fossils. (Bulman, 1970: V 6) Since the 1970s, as a result of advances in electron microscopy, graptolites have generally been thought to be most closely allied to the pterobranchs, a rare group of modern marine animals belonging to the phylum Hemichordata (hemichordates). Comparisons are drawn with the modern hemichordates ''Cephalodiscus'' and ''Rhabdopleura''. ''Cephalodiscus'' numbers about 18 species, and was first discovered in 1882. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Graptolithina」の詳細全文を読む スポンサード リンク
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