It is most famously known in (and most commonly associated with) Marrella,[1] and is also known in other organisms: for example, Aysheaia, where it protrudes from the anterior (and in one case posterior) end of the animal;[2] Hallucigenia,[3] Naraoia,[4] and Alalcomeneaus.[5] It is also present in other Lagerstätten, for example in Carboniferous crustacea from Ireland.[6]