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Waeringopteridae is a family of , an extinct group of aquatic . The Waeringopteridae is the only family classified as part of the superfamily Waeringopteroidea, which in turn is classified within the infraorder Diploperculata in the suborder Eurypterina. The earliest known member of the group, Orcanopterus, has been recovered from deposits of Katian (Late Ordovician) age and the latest known surviving member, Grossopterus, has been recovered from deposits of Siegenian (Early Devonian) age. The name Waeringopteridae is derived from the type genus Waeringopterus, which is named in honor of eurypterid researcher Erik N. Kjellesvig-Waering.
Waeringopterid fossils are very rare and the family only contains five known species classified in three different genera ( Waeringopterus, Orcanopterus and Grossopterus). Four of these species are from the ancient continent of Laurentia, with the only species known from outside of it being a Devonian species recovered from Germany. It is thus considered likely that the group originated in Laurentia before spreading to Germany during the Devonian. As the fossil record of the group is extremely poor, little is known of the morphology of the taxa within the group.
Although confirmed by phylogenetic analyses as monophyletic, and routinely used within eurypterid taxonomy,Dunlop, J. A., Penney, D. & Jekel, D. 2015. A summary list of fossil spiders and their relatives. In World Spider Catalog. Natural History Museum Bern, online at http://wsc.nmbe.ch , version 16.0 http://www.wsc.nmbe.ch/resources/fossils/Fossils16.0.pdf (PDF). "Waeringopteroidea" and "Waeringopteridae" were not formally published clades until 2025, the names instead deriving from a 2004 thesis by O. Erik Tetlie. Some researchers referred to the group more formally as the " waeringopteroid clade" rather than as the superfamily "Waeringopteroidea", pending a formal publication. However, the group name was formalised in a 2025 overview paper of eurypterid taxonomy.
Like all other Chelicerata, and other arthropods in general, waeringopterid eurypterids possessed segmented bodies and jointed appendages (limbs) covered in a cuticle composed of and chitin. The chelicerate body is divided into two tagmata (sections); the frontal prosoma (head) and posterior opisthosoma (abdomen). In the waeringopterids, the fifth pair of appendages were spiniferous. The telson (the posteriormost segment of the body) was xiphous (long and pointed). The eyes of waeringopterid eurypterids were located close to the marginal rim of the carapace (the "head" plate).
The waeringopterids were almost all small eurypterids. Waeringopterus cumberlandicus reached in length, while Grossopterus overathi reached . Orcanopterus manitoulinensis reached in length. Though this is relatively long in comparison to modern arthropods, other members of Diploperculata, such as the or the , reached much larger sizes, surpassing two meters.
"Waeringopteridae" and the superfamily that includes it, "Waeringopteroidea" (named after eurypterid researcher Erik N. Kjellesvig-Waering), were not formally published clades until 2025. The names originally derived from a 2004 thesis by O. Erik Tetlie and weew as such not actually technically valid names until a later paper formalised them. Nevertheless, as phylogenetic analyses confirmed the grouping as monophyletic and the names supply an easy way to refer to the group, they remained routinely used within studies centered around eurypterid taxonomy. In these studies, the names are usually within quotation marks and/or are noted to not be properly valid names that derive from a thesis. The group was also sometimes referred to as the "waeringopteroid clade" rather than as the "Waeringopteroidea" within studies to differentiate it from the properly described superfamilies, before the formal publication of Waeringopteroidea.
Distribution and paleobiogeography
Out of the five known waeringopterid species, four are from the fossil deposits in areas that were part of the ancient continent of Laurentia. Only the last known surviving species, Grossopterus, from the Devonian of Germany, is known from outside of Laurentia and it is thus assumed that the group originated in Laurentia before they spread to modern-day Germany in the Devonian. Further fossil finds are required to properly study the distribution and evolutionary history of the group. The temporal range of the group extends from the Late Ordovician ( Orcanopterus) to the Early Devonian ( Grossopterus).
See also
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