Editing Sea spider (section)

{{Short description|Class of marine arthropods}}
{{Automatic taxobox
| name = Sea spiders
| fossil_range = {{Fossil range|Late Cambrian|present}}
| image = <imagemap>
File:Pycnogonida collage.png|300px
rect 1 1 400 300 [[Palaeoisopus]]
rect 400 1 800 300 [[Flagellopantopus]]
rect 800 1 1200 300 [[Haliestes]]

rect 1 300 400 600 [[Austrodecidae]]
rect 400 300 800 600 [[Colossendeidae]]
rect 800 300 1200 600 [[Pycnogonidae]]

rect 1 600 400 900 [[Ammotheidae]]
rect 400 600 800 900 [[Endeinae]] 
rect 800 600 1200 900 [[Nymphonidae]]

</imagemap>
| image_caption =
| parent_authority = [[Pierre André Latreille|Latreille]], 1810
| taxon = Pycnogonida
| authority = [[Carl Eduard Adolph Gerstaecker|Gerstaecker]], 1863
| type_genus = '''''[[Pycnogonum]]'''''
| type_genus_authority = [[Morten Thrane Brünnich|Brünnich]], 1764
| subdivision_ranks = Orders and Families
| subdivision = See [[#Interrelationship|text]].
| synonyms = Arachnopoda <small>Dana, 1853</small>
}}

'''Sea spiders''' are marine [[arthropod]]s of the [[class (biology)|class]] '''Pycnogonida''',<ref>{{Merriam-Webster|Pycnogonida}}: "New Latin, from ''[[Pycnogonum]]'' [...] + ''{{linktext|-ida}}''"</ref> hence they are also called '''pycnogonids''' ({{IPAc-en|p|ɪ|k|ˈ|n|ɒ|ɡ|ə|n|ə|d|z}};<ref>{{MW|pycnogonid}}</ref> named after ''[[Pycnogonum]]'', the [[type genus]];<ref>{{cite web |title=pycnogonid |url=https://www.thefreedictionary.com/pycnogonid |work=The Free Dictionary |quote=From [[Neo-Latin]] Pycnogonida, class name, from {{lang|la|Pycnogonum}}, [[type genus]].}}</ref> with the suffix ''{{linktext|-id}}''). The class includes the only now-living [[order (biology)|order]] '''Pantopoda'''<ref>{{cite web |title=Pycnogonida |series=Taxon details |website=[[World Register of Marine Species]] |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=1302}}</ref> ({{abbr|lit.|literally}} ‘all feet’<ref>{{Merriam-Webster|Pantopoda}}: "taxonomic synonym of Pycnogonida < [[Neo-Latin]], from ''{{linktext|pant-}}'' + ''{{linktext|-poda}}''"</ref>), alongside a few fossil species which could trace back to the early or mid [[Paleozoic]].<ref name=":1">{{Cite journal |last1=Sabroux |first1=Romain |last2=Garwood |first2=Russell J. |last3=Pisani |first3=Davide |last4=Donoghue |first4=Philip C. J. |last5=Edgecombe |first5=Gregory D. |date=2024-10-14 |title=New insights into the Devonian sea spiders of the Hunsrück Slate (Arthropoda: Pycnogonida) |journal=PeerJ |language=en |volume=12 |pages=e17766 |doi=10.7717/peerj.17766 |doi-access=free |pmid=39421419 |pmc=11485130 |issn=2167-8359}}</ref> They are [[cosmopolitan distribution|cosmopolitan]], found in oceans around the world. The over 1,300 known species have leg spans ranging from {{convert|1|mm|in|abbr=on|2}} to over {{convert|70|cm|ft|abbr=on}}.<ref>{{cite press release |title=Sea spiders provide insights into Antarctic evolution |publisher=[[Department of the Environment and Energy]], Australian Antarctic Division |date=22 July 2010 |url=http://www.antarctica.gov.au/science/cool-science/2010/sea-spiders-provide-insights-into-antarctic-evolution |access-date=27 December 2017 |url-status=dead |archive-url=https://web.archive.org/web/20180731154307/http://www.antarctica.gov.au/science/cool-science/2010/sea-spiders-provide-insights-into-antarctic-evolution |archive-date=31 July 2018}}</ref> Most are toward the smaller end of this range in relatively shallow depths; however, they can grow to be quite large in [[Antarctic]] and [[deep-sea gigantism|deep waters]].

Despite their name and brief resemblance, "sea spiders" are not [[spider]]s, nor even [[arachnid]]s. While some literature around the 2000s suggests they may be a [[sister group]] to all other living arthropods,<ref name=":7">{{Cite journal |last1=Giribet |first1=Gonzalo |last2=Edgecombe |first2=Gregory D. |last3=Wheeler |first3=Ward C. |date=2001 |title=Arthropod phylogeny based on eight molecular loci and morphology |url=https://www.nature.com/articles/35093097 |journal=Nature |language=en |volume=413 |issue=6852 |pages=157–161 |doi=10.1038/35093097 |pmid=11557979 |bibcode=2001Natur.413..157G |issn=1476-4687|url-access=subscription }}</ref><ref name="Maxmen" /> their traditional classification as a member of [[chelicerates]] alongside [[Xiphosura|horseshoe crabs]] and arachnids has regained wide support in subsequent studies.<ref>{{Cite journal |last1=Giribet |first1=Gonzalo |last2=Edgecombe |first2=Gregory D. |date=2019 |title=The Phylogeny and Evolutionary History of Arthropods |url=https://linkinghub.elsevier.com/retrieve/pii/S0960982219304865 |journal=Current Biology |volume=29 |issue=12 |pages=R592–R602 |doi=10.1016/j.cub.2019.04.057 |pmid=31211983 |bibcode=2019CBio...29.R592G |issn=0960-9822}}</ref><ref>{{Cite journal |last=Edgecombe |first=Gregory D. |date=2020-11-02 |title=Arthropod Origins: Integrating Paleontological and Molecular Evidence |url=https://www.annualreviews.org/doi/10.1146/annurev-ecolsys-011720-124437 |journal=Annual Review of Ecology, Evolution, and Systematics |language=en |volume=51 |issue=1 |pages=1–25 |doi=10.1146/annurev-ecolsys-011720-124437 |issn=1543-592X|url-access=subscription }}</ref><ref name=":1" />