Graptolithinia

Graptolites Temporal range: Mid Cambrian to Carboniferous or Recent 510–320 Ma PreЄ Є O S D C P T J K Pg N Cryptograptus from the Silurian of South America. Specimen at the Royal Ontario Museum.
Scientific classification
Kingdom:	Animalia
Phylum:	Hemichordata
Class:	Pterobranchia
Subclass:	Graptolithina
Orders
†Graptoloidea & †Dendroidea

†Graptoloidea & †Dendroidea

Graptolithina is a subclass of the class Pterobranchia, the members of which are known as graptolites. These organisms are colonial animals known chiefly as fossils from the Middle Cambrian (Series 3, Stage 5) through the Lower Carboniferous (Mississippian) . A possible early graptolite, Chaunograptus, is known from the Middle Cambrian . One analysis suggests that the pterobranch Rhabdopleura represents extant graptolites . Studies on the tubarium of fossil and living graptolites showed similarities in the basic fusellar construction and it is considered that the group most probably evolved from a Rhabdopleura-like ancestor .

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; now they are widely recognized as hemichordates .

The name "graptolite" originates from the genus Graptolithus, which was used by Linnaeus in 1735 for inorganic mineralizations and incrustations 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). The term Graptolithina was established by Bronn in 1849 and later, Graptolithus was officially abandoned in 1954 by the ICZN .