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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 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.
Pterobranchia is a clade of small worm-shaped animals. They belong to the Hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles. There are about 25 known living pterobranch species in three genera, which are Rhabdopleura, Cephalodiscus, and Atubaria. On the other hand, there are several hundred extinct genera, some of which date from the Cambrian Period.
Rhabdopleurida is one of three orders in the class Pterobranchia, which are small, worm-shaped animals. Members belong to the hemichordates. Species in this order are sessile, colonial, connected with a stolon, living in clear water and secrete tubes called tubarium. They have a single gonad, the gill slits are absent and the collar has two tentaculated arms. Rhabdopleura is the best studied pterobranch in developmental biology. Some claim Rhabdopleura is an extant graptolite.
Rhabdopleura is a genus of colonial sessile hemichordates belonging to the Pterobranchia class. As one of the oldest living genera with a fossil record dating back to the Middle Cambrian, it is also considered to be the only living genus of graptolites.
Monograptidae is an extinct family of graptolites of the Order Graptoloidea. Monograptids have only one row of thecae per stipe, unlike the biserial graptolites which have two opposing rows of thecae per stipe.
Anisograptidae is an extinct family of graptolites. As the first planktic graptolites, they play a crucial role for understanding the transition of graptolites from ocean floor suspension feeders to ocean surface plankton during the early Ordovician.
Sigmagraptidae is an extinct family of graptolites.
Sinograptidae is an extinct family of graptolites.
Dichograptidae is an extinct family of graptolites. Fossils are found mostly from the Late Ordovician to the Early Devonian.
Didymograptidae is an extinct family of graptolites.
Glossograptidae is an extinct family of graptolites.
Diplograptidae is an extinct family of graptolites.
Lasiograptidae is an extinct family of graptolites.
Climacograptidae is an extinct family of graptolites.
Dicranograptidae is an extinct family of graptolites.
Normalograptidae is an extinct family of graptolites.
Neodiplograptidae is an extinct family of graptolites.
Retiolitidae is an extinct family of graptolites characterized by meshwork-like tubaria.
Dimorphograptidae is an extinct family of graptolites.
Dendrograptidae is an extinct family of graptolites.
References
- ↑ Maletz, Jörg (2017). Graptolite Paleobiology. Wiley-Blackwell. ISBN 9781118515617.
- ↑ Maletz, Jörg (2014). "The classification of the Pterobranchia (Cephalodiscida and Graptolithina)". Bulletin of Geosciences. 89 (3): 477–540. doi: 10.3140/bull.geosci.1465 . ISSN 1214-1119.
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