Editing Graptolite (section)

==Ecology==
[[File:Graptolite appendages.png|thumb|150px|Hypothetical zooid inspired by modern [[Pteropoda|pteropods]], with swimming appendages developed from the cephalic shield.]]
Graptolites were a major component of the early [[Paleozoic]] ecosystems, especially for the [[zooplankton]] because the most abundant and diverse species were planktonic. Graptolites were most likely suspension feeders and strained the water for food such as plankton.<ref>{{Cite web|url=http://samnoblemuseum.ou.edu/common-fossils-of-oklahoma/invertebrate-fossils/graptolites/|title=Graptolites|website=samnoblemuseum.ou.edu|access-date=2018-12-28}}</ref>

Inferring by analogy with modern pterobranchs, they were able to migrate vertically through the water column for feeding efficiency and to avoid predators. With ecological models and studies of the [[facies]], it was observed that, at least for Ordovician species, some groups of species are largely confined to the [[epipelagic]] and [[mesopelagic]] zone, from inshore to open ocean.<ref name= Cooper2012>Cooper, R., [[Sue Rigby|Rigby, S.]], Loydell, D. & Bates, D. (2012) Palaeoecology of the Graptoloidea. ''Earth-Science Reviews'', 112(1):23-41.</ref> Living rhabdopleura have been found in deep waters in several regions of Europe and America but the distribution might be biased by sampling efforts; colonies are usually found as [[epibiont]]s of shells.

Their locomotion was relative to the water mass in which they lived but the exact mechanisms (such as turbulence, [[buoyancy]], active swimming, and so forth) are not clear yet. One proposal, put forward by Melchin and DeMont (1995), suggested that graptolite movement was analogous to modern free-swimming animals with heavy housing structures. In particular, they compared graptolites to "sea butterflies" ([[Sea butterfly|Thecostomata]]), small swimming [[Pteropoda|pteropod]] [[Snail|snails]]. Under this suggestion, graptolites moved through [[rowing]] or swimming via an undulatory movement of paired muscular [[appendages]] developed from the cephalic shield or feeding tentacles. In some species, the thecal aperture was probably so restricted that the appendages hypothesis is not feasible. On the other hand, buoyancy is not supported by any extra thecal tissue or gas build-up control mechanism, and active swimming requires a lot of energetic waste, which would rather be used for the tubarium construction.<ref name="Cooper2012" />

There are still many questions regarding graptolite locomotion but all these mechanisms are possible alternatives depending on the species and its habitat. For benthic species, that lived attached to the sediment or any other organism, this was not a problem; the zooids were able to move but restricted within the tubarium. Although this zooid movement is possible in both planktic and benthic species, it is limited by the [[stolon]] but is particularly useful for feeding. Using their arms and tentacles, which are close to the mouth, they filter the water to catch any particles of food.<ref name="Cooper2012" />