Editing Agnostida (section)

==Ecology==
Scientists have long debated whether the agnostids lived a [[pelagic]] or a [[benthic]] lifestyle. Their lack of eyes, a morphology not well-suited for swimming, and their fossils found in association with other benthic trilobites suggest a benthic (bottom-dwelling) mode of life. They are likely to have lived on areas of the ocean floor which received little or no light and fed on [[detritus]] which descended from upper layers of the sea to the bottom. Their wide geographic dispersion in the [[fossil record]] is uncharacteristic of benthic animals, suggesting a pelagic existence. The thoracic segment appears to form a hinge between the head and pygidium allowing for a bivalved [[ostracod]]an-type lifestyle. The orientation of the thoracic appendages appears ill-suited for benthic living. Recent work suggests that some agnostids were benthic predators, engaging in cannibalism and possibly pack-hunting behavior.<ref>{{cite journal | vauthors = McMenamin MA | title = Cambrian cannibals: agnostid trilobite ethology and the earliest known case of arthropod cannibalism. | journal = Geological Society of America Abstracts with Programs | date = October 2010 | volume = 42 | issue = 5 | page = 320 }}</ref>

They are sometimes preserved within the voids of other organisms, for instance within empty [[hyolith]] conchs,<ref>{{cite journal | vauthors = Fatka O, Vokáč V, Moravec J, Šinágl M, Valent M | title = Agnostids entombed in hyolith conchs. | journal = Memoirs of the Association of Australasian Palaeontologists | date = January 2009 | volume = 37 | pages = 481–489 }}</ref> within [[sponge]]s, [[Selkirkia|worm tubes]] and under the carapaces of [[Sidneyia|bivalved arthropods]],<ref name=Chatterton_2003>{{Chatterton 2003|name-list-style=vanc}}</ref> presumably in order to hide from predators or strong storm currents; or maybe whilst scavenging for food.<ref name=Chatterton_2003/> In the case of the tapering worm tubes ''[[Selkirkia]]'', trilobites are always found with their heads directed towards the opening of the tube, suggesting that they reversed in; the absence of any moulted carapaces suggests that moulting was not their primary reason for seeking shelter.<ref name=Chatterton_2003/>