Offacolus: Difference between revisions
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'''''Offacolus''''' is an [[extinct]] [[genus]] of [[euchelicerate]], a group of [[chelicerate]] [[arthropods]]. Its only species, ''O. kingi'', has been found in deposits from the [[Silurian]] [[Geological period|period]] ([[Homerian]] [[Epoch (geology)|epoch]]) in the [[Wenlock Series Lagerstätte]] of [[Herefordshire]], [[England]]. It is |
'''''Offacolus''''' is an [[extinct]] [[genus]] of [[euchelicerate]], a group of [[chelicerate]] [[arthropods]]. Its only species, ''O. kingi'', has been found in deposits from the [[Silurian]] [[Geological period|period]] ([[Homerian]] [[Epoch (geology)|epoch]]) in the [[Wenlock Series Lagerstätte]] of [[Herefordshire]], [[England]]. It is the only member of the [[monotypic]] [[Family (biology)|family]] Offacolidae, and classified as a [[Basal (phylogenetics)|basal]] ("primitive") genus in the [[clade]] Euchelicerata, along with ''[[Dibasterium]]'' and [[Prosomapoda]]. The genus is named after [[Offa]], a king from the ancient kingdom of [[Mercia]], and ''colus'', a person who dwelled among (this time referring to) the [[Offa's Dyke]]. The species name honors Robert Joseph King, a British [[mineralogist]] who found the fossils of ''Offacolus''.<ref name=":0">{{cite journal|title=A new arthropod from the Silurian Konservat–Lagerstätte of Herefordshire, UK|first1=Patrick J.|last1=Orr|first2=Derek J.|last2=Siveter|first3=Derek E. G.|last3=Briggs|authorlink3=Derek Briggs|first4=David J.|last4=Siveter|first5=Mark D.|last5=Sutton|journal= Proceedings of the Royal Society of London. Series B: Biological Sciences|volume=267|issue=1452|pages=1497–1504|year=2000|doi=10.1098/rspb.2000.1170|pmid=11007324|pmc=1690702|issn=1471-2954}}</ref> |
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[[File:20201122 Offacolus kingi ventral appendages.png|300px|thumb|Ventral appendages of ''Offacolus kingi'', showing limb-like exopods (Ex2-5)]] |
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Similar to ''Dibasterium'', ''Offacolus'' posses limb-like exopods (outer limb branches) on appendage II to V,<ref name=":1">{{Cite journal|last=Sutton|first=Mark D.|last2=Briggs|first2=Derek E. G.|last3=Siveter|first3=David J.|last4=Siveter|first4=Derek J.|last5=Orr|first5=Patrick J.|date=2002-06-22|title=The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities|url=https://royalsocietypublishing.org/doi/10.1098/rspb.2002.1986|journal=Proceedings of the Royal Society of London. Series B: Biological Sciences|volume=269|issue=1497|pages=1195–1203|doi=10.1098/rspb.2002.1986|pmc=PMC1691018|pmid=12065034}}</ref><ref>{{Cite journal|last=Dunlop|first=Jason A.|last2=Lamsdell|first2=James C.|title=Segmentation and tagmosis in Chelicerata|url=https://www.academia.edu/28212892/Segmentation_and_tagmosis_in_Chelicerata|journal=Arthropod Structure & Development|language=en|volume=46|issue=3|pages=395|issn=1467-8039}}</ref> a character suggest to be [[plesiomorphic]] (observable in the putative stem-chelicerate taxon [[Habeliida]]<ref>{{Cite journal|last=Aria|first=Cédric|last2=Caron|first2=Jean-Bernard|date=2017-12-21|title=Mandibulate convergence in an armoured Cambrian stem chelicerate|url=https://doi.org/10.1186/s12862-017-1088-7|journal=BMC Evolutionary Biology|volume=17|issue=1|pages=261|doi=10.1186/s12862-017-1088-7|issn=1471-2148|pmc=PMC5738823|pmid=29262772}}</ref>) and lost within the prosomapod clade.<ref name=":2" /> |
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==Classification== |
==Classification== |
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''Offacolus'' is the only [[genus]] in the [[monotypic]] [[Family (biology)|family]] Offacolidae, classified in the [[clade]] [[Euchelicerata]] together with the genus ''[[Dibasterium]]'' and the clade [[Prosomapoda]]. |
''Offacolus'' was originally described as an [[arthropod]] with [[chelicerate]] affinities,<ref name=":0" /> with detailed redescription done by Sutton ''et al.'' 2002 further suggested it to be unambiguously a chelicerate arthropod.<ref name=":1" /> ''Offacolus'' is the only [[genus]] in the [[monotypic]] [[Family (biology)|family]] Offacolidae,<ref name=":1" /> classified in the [[clade]] [[Euchelicerata]] together with the genus ''[[Dibasterium]]'' and the clade [[Prosomapoda]].<ref name=":2" /> |
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A phylogenetic analysis (the results presented in a cladogram below) conducted by James Lamsdell in 2013 on the relationships within the Xiphosura and the relations to other closely related groups concluded that the Xiphosura, as presently understood, was [[paraphyletic]] (a group sharing a [[Last Common Ancestor|last common ancestor]] but not including all descendants of this ancestor) and thus not a valid phylogenetic group. ''Offacolus'' was recovered as the [[sister taxon]] (closest relative) of Prosomapoda.<ref>{{Cite journal|title=Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura|last=Lamsdell|first=James C.|year=2012|journal=Zoological Journal of the Linnean Society|volume=167|issue=1|pages=1–27|doi=10.1111/j.1096-3642.2012.00874.x|issn=0024-4082|doi-access=free}}</ref> |
A phylogenetic analysis (the results presented in a cladogram below) conducted by James Lamsdell in 2013 on the relationships within the Xiphosura and the relations to other closely related groups concluded that the Xiphosura, as presently understood, was [[paraphyletic]] (a group sharing a [[Last Common Ancestor|last common ancestor]] but not including all descendants of this ancestor) and thus not a valid phylogenetic group. ''Offacolus'' was recovered as the [[sister taxon]] (closest relative) of Prosomapoda.<ref name=":2">{{Cite journal|title=Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura|last=Lamsdell|first=James C.|year=2012|journal=Zoological Journal of the Linnean Society|volume=167|issue=1|pages=1–27|doi=10.1111/j.1096-3642.2012.00874.x|issn=0024-4082|doi-access=free}}</ref> |
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Revision as of 13:54, 1 December 2020
| Offacolus Temporal range: Homerian, ~
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| Reconstruction of Offacolus kingi | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Clade: | Euchelicerata |
| Family: | †Offacolidae Sutton et al., 2002 |
| Genus: | †Offacolus Orr et al., 2000 |
| Type species | |
| †Offacolus kingi Orr et al., 2000
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Offacolus is an extinct genus of euchelicerate, a group of chelicerate arthropods. Its only species, O. kingi, has been found in deposits from the Silurian period (Homerian epoch) in the Wenlock Series Lagerstätte of Herefordshire, England. It is the only member of the monotypic family Offacolidae, and classified as a basal ("primitive") genus in the clade Euchelicerata, along with Dibasterium and Prosomapoda. The genus is named after Offa, a king from the ancient kingdom of Mercia, and colus, a person who dwelled among (this time referring to) the Offa's Dyke. The species name honors Robert Joseph King, a British mineralogist who found the fossils of Offacolus.[1]
Similar to Dibasterium, Offacolus posses limb-like exopods (outer limb branches) on appendage II to V,[2][3] a character suggest to be plesiomorphic (observable in the putative stem-chelicerate taxon Habeliida[4]) and lost within the prosomapod clade.[5]
Classification
Offacolus was originally described as an arthropod with chelicerate affinities,[1] with detailed redescription done by Sutton et al. 2002 further suggested it to be unambiguously a chelicerate arthropod.[2] Offacolus is the only genus in the monotypic family Offacolidae,[2] classified in the clade Euchelicerata together with the genus Dibasterium and the clade Prosomapoda.[5]
A phylogenetic analysis (the results presented in a cladogram below) conducted by James Lamsdell in 2013 on the relationships within the Xiphosura and the relations to other closely related groups concluded that the Xiphosura, as presently understood, was paraphyletic (a group sharing a last common ancestor but not including all descendants of this ancestor) and thus not a valid phylogenetic group. Offacolus was recovered as the sister taxon (closest relative) of Prosomapoda.[5]
References
- ^ a b Orr, Patrick J.; Siveter, Derek J.; Briggs, Derek E. G.; Siveter, David J.; Sutton, Mark D. (2000). "A new arthropod from the Silurian Konservat–Lagerstätte of Herefordshire, UK". Proceedings of the Royal Society of London. Series B: Biological Sciences. 267 (1452): 1497–1504. doi:10.1098/rspb.2000.1170. ISSN 1471-2954. PMC 1690702. PMID 11007324.
- ^ a b c Sutton, Mark D.; Briggs, Derek E. G.; Siveter, David J.; Siveter, Derek J.; Orr, Patrick J. (2002-06-22). "The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities". Proceedings of the Royal Society of London. Series B: Biological Sciences. 269 (1497): 1195–1203. doi:10.1098/rspb.2002.1986. PMC 1691018. PMID 12065034.
{{cite journal}}: CS1 maint: PMC format (link) - ^ Dunlop, Jason A.; Lamsdell, James C. "Segmentation and tagmosis in Chelicerata". Arthropod Structure & Development. 46 (3): 395. ISSN 1467-8039.
- ^ Aria, Cédric; Caron, Jean-Bernard (2017-12-21). "Mandibulate convergence in an armoured Cambrian stem chelicerate". BMC Evolutionary Biology. 17 (1): 261. doi:10.1186/s12862-017-1088-7. ISSN 1471-2148. PMC 5738823. PMID 29262772.
{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link) - ^ a b c Lamsdell, James C. (2012). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi:10.1111/j.1096-3642.2012.00874.x. ISSN 0024-4082.
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