:en:Plesiosiro
{{Short description|Extinct genus of arachnids}}
{{Speciesbox
| display_parents = 3
| taxon = Plesiosiro madeleyi
| image = Plesiosiro madeleyi CT.jpg
| image_caption = CT scan
| image2 = 20200823 Plesiosiro madeleyi.png
| image2_caption = Life restoration
| fossil_range = {{fossil range|Upper Carboniferous}}
| grandparent_authority = Pocock, 1911
| parent_authority = Pocock, 1911
| authority = Pocock, 1911
}}
Plesiosiro is an extinct arachnid genus known exclusively from nine specimens from the Upper Carboniferous of Coseley, Staffordshire, United Kingdom.{{cite journal|last1=Garwood|first1=Russell J.|last2=Dunlop|first2=Jason|title=Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders|journal=PeerJ|volume=2|year=2014|pages=e641|issn=2167-8359|doi=10.7717/peerj.641|pmid=25405073|pmc=4232842|doi-access=free}}{{cite journal|last1=Dunlop|first1=Jason A.|title=A redescription of the Carboniferous arachnid Plesiosiro madeleyi Pocock, 1911 (Arachnida: Haptopoda)|journal=Transactions of the Royal Society of Edinburgh: Earth Sciences|volume=90|issue=1|year=2011|pages=29–47|issn=0263-5933|doi=10.1017/S0263593300002492}} The genus is monotypic, represented only by the species Plesiosiro madeleyi described by Reginald Innes Pocock in his important 1911 monograph on British Carboniferous arachnids. It is the only known member of the order Haptopoda.{{cite book |author=Reginald Innes Pocock |author-link=Reginald Innes Pocock |year=1911 |title=A Monograph of the Terrestrial Carboniferous Arachnida of Great Britain |url=https://archive.org/details/monographofterre00poco |series=Monographs of the Palaeontographical Society, London |pages=[https://archive.org/details/monographofterre00poco/page/1 1]–84}}
The original fossils have been redescribed in detail by Alexander Petrunkevitch in 1949{{cite journal |author=Alexander Petrunkevitch |author-link=Alexander Petrunkevitch |year=1949 |title=A study of Palaeozoic Arachnida |journal=Transactions of the Connecticut Academy of Arts and Sciences |volume=37 |pages=69–315}} and Dunlop in 1999. A supposed example from the Coal Measures of Lancashire is a misidentification.
Relationships
Plesiosiro means "close to Siro", which is a genus of cyphophthalmid (Cyphophthalmi); the most primitive group of the living harvestmen (Opiliones). These harvestmen do, in some ways, resemble the reconstructed body plan of the haptopods.
Revisions have confirmed that Haptopoda should be treated as a separate and independent order. A 2007 study tentatively recognised a group named Schizotarsata Shultz, 2007{{cite journal |author=Jeffrey W. Shultz |year=2007 |title=A phylogenetic analysis of the arachnid orders based on morphological characters |journal=Zoological Journal of the Linnean Society |volume=150 |issue=2 |pages=221–265 |doi=10.1111/j.1096-3642.2007.00284.x |url=http://www.museunacional.ufrj.br/mndi/Aracnologia/pdfliteratura/Shultz%202007%20Phylogenetic%20analysis%20Arachnida.pdf |doi-access=free }} comprising Haptopoda, Amblypygi (whip spiders), Uropygi (whip scorpions) and Schizomida (schizomids), which has been recovered subsequently in a number of other phylogenies to include fossils.{{cite journal|last1=Wang|first1=Bo|last2=Dunlop|first2=Jason A.|last3=Selden|first3=Paul A.|last4=Garwood|first4=Russell J.|last5=Shear|first5=William A.|last6=Müller|first6=Patrick|last7=Lei|first7=Xiaojie|title=Cretaceous arachnid Chimerarachne yingi gen. et sp. nov. illuminates spider origins|journal=Nature Ecology & Evolution|volume=2|issue=4|year=2018|pages=614–622|issn=2397-334X|doi=10.1038/s41559-017-0449-3|pmid=29403075|bibcode=2018NatEE...2..614W |s2cid=4239867|url=https://www.research.manchester.ac.uk/portal/en/publications/cretaceous-arachnid-chimerarachne-yingi-gen-et-sp-nov-illuminates-spider-origins(b82d83bd-6081-4187-acfc-fb7358c33358).html}}{{cite journal|last1=Garwood|first1=Russell J.|last2=Dunlop|first2=Jason A.|last3=Knecht|first3=Brian J.|last4=Hegna|first4=Thomas A.|title=The phylogeny of fossil whip spiders|journal=BMC Evolutionary Biology|volume=17|issue=1|year=2017|page=105|issn=1471-2148|doi=10.1186/s12862-017-0931-1|pmid=28431496|pmc=5399839|doi-access=free|bibcode=2017BMCEE..17..105G }}{{cite journal|last1=Garwood|first1=Russell J.|last2=Dunlop|first2=Jason A.|last3=Selden|first3=Paul A.|last4=Spencer|first4=Alan R. T.|last5=Atwood|first5=Robert C.|last6=Vo|first6=Nghia T.|last7=Drakopoulos|first7=Michael|title=Almost a spider: a 305-million-year-old fossil arachnid and spider origins|journal=Proceedings of the Royal Society B: Biological Sciences|volume=283|issue=1827|year=2016|pages=20160125|issn=0962-8452|doi=10.1098/rspb.2016.0125|pmid=27030415|doi-access=free|pmc=4822468}} All share the character of a subdivided tarsus (or foot) which gives the group its name. A 2014 analysis found that Plesiosiro had chelicerae consisting of two elements, a basal paturon and a fang, which suggests a position within Tetrapulmonata. Under both equal and implied weights, Plesisiro was found to be the most basal member of a clade containing Amblypygi, Schizomida, and Uropygi (Thelyphonida s.s.), which was sister to the clade containing Araneae and Uraraneida.
Names
The order has also been called Haptopodida; the ending -ida originated when Petrunkevitch (1955){{cite book |author=Alexander Petrunkevitch |author-link=Alexander Petrunkevitch |year=1955 |chapter=Arachnida |pages=42–162 |editor=R. C. Moore |series=Treatise on Invertebrate Paleontology |title=Part P, Arthropoda 2 |publisher=Geological Society of America and University of Kansas Press |location=Lawrence}} tried to standardize the endings of the arachnid orders.
Haptopoda originates from Greek "haptos" (= tangible, subject to the sense of touch) + "pous, podos" (= foot) and refers to its quite long front pair of legs with their subdivided tips which look as though they might have been used to 'feel' their way around in front of the animal.
References
{{Reflist|26em}}
{{Arachnida|extinct}}
{{Taxonbar|from=Q19129}}
Category:Carboniferous arachnids
Category:Monotypic prehistoric arachnid genera
Category:Carboniferous arthropods of Europe
Category:Carboniferous England