Editing Sea spider (section)

==Taxonomy==
===Phylogenetic position===
{{cladogram
|title=
|align= right
|caption=Best-supported position of Pycnogonida
|cladogram=
{{clade| style=width:30em;font-size:100%;line-height:100%
|1={{clade
  |label1=[[Chelicerata]]|1={{clade
    |1='''Pycnogonida'''
    |label2=Euchelicerata|2=[[Xiphosura]] and [[Arachnida]]
}}
    |label2=[[Mandibulata]]|2={{clade
      |1=[[Myriapoda]]
      |label2=[[Pancrustacea]]|2=[[Crustacea]] and [[Hexapoda]]
}} }} }} }}
{{cladogram
|title=
|align= right
|caption=Cormogonida hypothesis
|cladogram=
{{clade| style=width:30em;font-size:100%;line-height:100%
|1={{clade
  |1='''Pycnogonida'''
  |label2=Cormogonida |2={{clade
    |label1=Euchelicerata|1=[[Xiphosura]] and [[Arachnida]]
      |2=[[Myriapoda]]
      |label3=[[Pancrustacea]]|3=[[Crustacea]] and [[Hexapoda]]
}} }} }} }}
Sea spiders had been interpreted as some kind of [[arachnid]]s or [[crustacean]]s in historical studies.<ref name=":10" /> However, after the concept of [[Chelicerata]] being established in 20th century, sea spiders have long been considered part of the subphylum, alongside euchelicerate taxa such as [[Xiphosura]] (horseshoe crabs) and Arachnida ([[spider]]s, [[scorpion]]s, [[mite]]s, [[tick]]s, [[harvestmen]] and other lesser-known orders).<ref name="Margulis & Schwartz">{{Cite book |last1=Margulis |first1=Lynn |author-link=Lynn Margulis |last2=Schwartz |first2=Karlene |title=Five Kingdoms, An Illustrated Guide to the Phyla of Life on Earth |publisher=W.H. Freeman and Company |year=1998 |edition=third |isbn=978-0-7167-3027-9 |url-access=registration |url=https://archive.org/details/fivekingdomsillu00marg_0 }}{{page needed|date=March 2015}}</ref>

A competing hypothesis around 2000s proposes that Pycnogonida belong to their own lineage, [[sister group|sister]] to the lineage lead to other extant arthropods (i.e. euchelicerates, [[myriapod]]s, crustaceans and [[Hexapoda|hexapod]]s, collectively known as Cormogonida). This Cormogonida hypothesis was first indicated by early phylogenomic analysis aroud that time,<ref name=":7" /> followed by another study suggest that the sea spider's chelifores are not positionally [[Homology (biology)|homologous]] to the chelicerae of euchelicerates (originated from the deutocerebral segment/somite 1), as was previously supposed. Instead, the chelifore nerves were thought to be innervated by the [[protocerebrum]], the first segment of the [[arthropod brain]] which corresponded to the ocular somite, bearing the [[Arthropod eye|eyes]] and [[Labrum (arthropod mouthpart)|labrum]]. This condition of having paired protocerebral appendages is not found anywhere else among arthropods, except in other [[panarthropod]]s such as [[onychophora]]n (primary antennae) and contestably<ref>{{Cite journal |last1=Moysiuk |first1=Joseph |last2=Caron |first2=Jean-Bernard |date=2022-08-08 |title=A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation |url=https://www.sciencedirect.com/science/article/pii/S0960982222009861 |journal=Current Biology |volume=32 |issue=15 |pages=3302–3316.e2 |doi=10.1016/j.cub.2022.06.027 |pmid=35809569 |bibcode=2022CBio...32E3302M |issn=0960-9822}}</ref> in [[Cambrian]] stem-group arthropods like [[radiodont]]s (frontal appendages), which was taken as evidence that Pycnogonida may be basal than all other living arthropods, since the protocerebral appendages were thought to be reduced and fused into a labrum in the last common ancestor of crown-group arthropods, and pycnogonids did not have a labrum coexist with the chelifores. If that's true, it would have meant the sea spiders are the last surviving (and highly modified) members of an ancient, basal arthropods that originated in Cambrian oceans.<ref name="Maxmen">{{cite journal |doi=10.1038/nature03984 |pmid=16237442 |title=Neuroanatomy of sea spiders implies an appendicular origin of the protocerebral segment |journal=Nature |volume=437 |issue=7062 |pages=1144–8 |year=2005 |last1=Maxmen |first1=Amy |last2=Browne |first2=William E. |last3=Martindale |first3=Mark Q. |last4=Giribet |first4=Gonzalo |bibcode=2005Natur.437.1144M |s2cid=4400419 }}</ref> However, the basis of this hypothesis was immediately refuted by subsequent studies using [[Hox gene]] expression patterns, demonstrated the developmental homology between chelicerae and chelifores, with chelifore nerves innervated by a deuterocerebrum that has been rotated forwards, which was misinterpreted as protocerebrum by the aforementioned study.<ref name="Jager">{{cite journal |doi=10.1038/nature04591 |pmid=16724066 |title=Homology of arthropod anterior appendages revealed by Hox gene expression in a sea spider |journal=Nature |volume=441 |issue=7092 |pages=506–8 |year=2006 |last1=Jager |first1=Muriel |last2=Murienne |first2=Jérôme |last3=Clabaut |first3=Céline |last4=Deutsch |first4=Jean |last5=Guyader |first5=Hervé Le |last6=Manuel |first6=Michaël |bibcode=2006Natur.441..506J |s2cid=4307398 }}</ref><ref name="PZ Myers">{{Cite web|title=Chelifores, chelicerae, and invertebrate evolution &#124; ScienceBlogs|url=https://scienceblogs.com/pharyngula/2006/05/26/chelifores-chelicerae-and-inve|access-date=2022-01-10|website=scienceblogs.com}}</ref><ref name=":6">{{Cite journal |last1=Brenneis |first1=Georg |last2=Ungerer |first2=Petra |last3=Scholtz |first3=Gerhard |date=2008-10-27 |title=The chelifores of sea spiders (Arthropoda, Pycnogonida) are the appendages of the deutocerebral segment: Chelifores of sea spiders |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1525-142X.2008.00285.x |journal=Evolution & Development |language=en |volume=10 |issue=6 |pages=717–724 |doi=10.1111/j.1525-142X.2008.00285.x|pmid=19021742 |s2cid=6048195 |url-access=subscription }}</ref>

[[File:20191107 Panarthropoda head segments appendages extant en.png|thumb|600px|Alignment of anterior somites and appendages of extant panarthropods, with chelifores (Chf) indicated as deutocerebral (D, yellow) somite 1 appendages. Dark grey indicating head somites.]]
Since 2010s, the chelicerate affinity of Pycnogonida regain wide support as the sister group of Euchelicerata. Under the basis of phylogenomics, this is one of the only stable topology of chelicerate interrelationships in contrast to the uncertain relationship of many euchelicerate taxa (e.g. poorly resolved position of arachnid orders other than [[tetrapulmonate]]s and [[scorpion]]s; non-monophyly of Arachnida in respect to Xiphosura).<ref name="Regieretal2010">{{cite journal |last1=Regier |first1=Jerome C. |last2=Shultz |first2=Jeffrey W. |last3=Zwick |first3=Andreas |last4=Hussey |first4=April |last5=Ball |first5=Bernard |last6=Wetzer |first6=Regina |last7=Martin |first7=Joel W. |last8=Cunningham |first8=Clifford W. |year=2010 |title=Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences |journal=Nature |volume=463 |issue=7284 |pages=1079–83 |bibcode=2010Natur.463.1079R |doi=10.1038/nature08742 |pmid=20147900 |s2cid=4427443}}</ref><ref>{{Cite journal |last1=Sharma |first1=Prashant P. |last2=Kaluziak |first2=Stefan T. |last3=Pérez-Porro |first3=Alicia R. |last4=González |first4=Vanessa L. |last5=Hormiga |first5=Gustavo |last6=Wheeler |first6=Ward C. |last7=Giribet |first7=Gonzalo |date=November 2014 |title=Phylogenomic Interrogation of Arachnida Reveals Systemic Conflicts in Phylogenetic Signal |url=https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msu235 |journal=Molecular Biology and Evolution |language=en |volume=31 |issue=11 |pages=2963–2984 |doi=10.1093/molbev/msu235 |pmid=25107551 |issn=1537-1719|doi-access=free }}</ref><ref>{{Cite journal |last1=Ballesteros |first1=Jesús A |last2=Sharma |first2=Prashant P |date=2019-11-01 |editor-last=Halanych |editor-first=Ken |title=A Critical Appraisal of the Placement of Xiphosura (Chelicerata) with Account of Known Sources of Phylogenetic Error |url=https://academic.oup.com/sysbio/article/68/6/896/5319972 |journal=Systematic Biology |language=en |volume=68 |issue=6 |pages=896–917 |doi=10.1093/sysbio/syz011 |pmid=30917194 |issn=1063-5157|doi-access=free }}</ref><ref>{{Cite journal |last1=Ballesteros |first1=Jesús A. |last2=Santibáñez López |first2=Carlos E. |last3=Kováč |first3=Ľubomír |last4=Gavish-Regev |first4=Efrat |last5=Sharma |first5=Prashant P. |date=2019-12-18 |title=Ordered phylogenomic subsampling enables diagnosis of systematic errors in the placement of the enigmatic arachnid order Palpigradi |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=286 |issue=1917 |pages=20192426 |doi=10.1098/rspb.2019.2426 |issn=0962-8452 |pmc=6939912 |pmid=31847768}}</ref><ref>{{Cite journal |last1=Ballesteros |first1=Jesús A |last2=Santibáñez-López |first2=Carlos E |last3=Baker |first3=Caitlin M |last4=Benavides |first4=Ligia R |last5=Cunha |first5=Tauana J |last6=Gainett |first6=Guilherme |last7=Ontano |first7=Andrew Z |last8=Setton |first8=Emily V W |last9=Arango |first9=Claudia P |last10=Gavish-Regev |first10=Efrat |last11=Harvey |first11=Mark S |last12=Wheeler |first12=Ward C |last13=Hormiga |first13=Gustavo |last14=Giribet |first14=Gonzalo |last15=Sharma |first15=Prashant P |date=2022-02-03 |editor-last=Teeling |editor-first=Emma |title=Comprehensive Species Sampling and Sophisticated Algorithmic Approaches Refute the Monophyly of Arachnida |url=https://academic.oup.com/mbe/article/doi/10.1093/molbev/msac021/6522129 |journal=Molecular Biology and Evolution |language=en |volume=39 |issue=2 |pages=msac021 |doi=10.1093/molbev/msac021 |issn=0737-4038 |pmc=8845124 |pmid=35137183}}</ref> This is consistent with the chelifore-chelicera homology, as well as other morphological similarities and differences between pycnogonids and euchelicerates.<ref name=":10">{{cite journal |doi=10.1111/j.1439-0469.2004.00284.x |title=Pycnogonid affinities: A review |journal=Journal of Zoological Systematics and Evolutionary Research |volume=43 |pages=8–21 |year=2005 |last1=Dunlop |first1=J. A. |last2=Arango |first2=C. P. |citeseerx=10.1.1.714.8297 }}</ref> However, due to pycnogonid's highly modified anatomy and lack of intermediate fossils, their evolutional origin and relationship with the basal fossil chelicerates (such as [[Habeliida|habeliids]] and ''[[Mollisonia]]'') are still difficult to compare and interpret.<ref>{{Cite journal |last1=Aria |first1=Cédric |last2=Caron |first2=Jean-Bernard |date=2019 |title=A middle Cambrian arthropod with chelicerae and proto-book gills |url=https://www.nature.com/articles/s41586-019-1525-4 |journal=Nature |language=en |volume=573 |issue=7775 |pages=586–589 |doi=10.1038/s41586-019-1525-4 |pmid=31511691 |bibcode=2019Natur.573..586A |issn=1476-4687|url-access=subscription }}</ref>

===Interrelationship===
{{cladogram
|title=
|align= right
|caption= Internal phylogeny of Pycnogonida.<ref name=":0" /><ref name=":14" />
|cladogram=
{{clade| style=width:35em;font-size:90%;line-height:100%
|1={{clade
|state1=double|label1=?|1=stem-groups (e.g. ''[[Palaeoisopus]]'',  ''[[Flagellopantopus]]'', ''[[Palaeopantopus]]'')
|label2=Pantopoda|2={{clade
 |label1=Stiripasterida|1=[[Austrodecidae]]
 |label2=Eupantopodida|2={{clade
  |1={{clade
  |label1=Colossendeoidea|1={{clade
  |1=[[Colossendeidae]]
  |2={{clade
   |1=[[Rhynchothoracidae]] 
   |2=[[Pycnogonidae]]
}} }} }}
   |2={{clade
    |1={{clade
     |label1=Phoxichilidioidea|1={{clade
      |1=[[Endeidae]] 
      |2=[[Phoxichilidiidae]]
}}
     |label2=Ammotheoidea|2={{clade
      |1=[[Pallenopsidae]]
      |2=[[Ammotheidae]]
}} }}
    |label2=?|2=[[Ascorhynchidae]]<br>(including ''[[Nymphonella]]''?)
      |3={{clade|label1=Nymphonoidea|1={{clade
       |state1=double|1=[[Callipallenidae]]<br>([[paraphyletic]])
       |2=[[Nymphonidae]]
}} }} }} }} }} }} }} }}
The class Pycnogonida comprises over 1,300 [[species]], which are split into over 80 [[Genus|genera]]. All extant genera are considered part of the single [[Order (biology)|order]] Pantopoda, which was subdivided into 11 [[family (biology)|families]]. Historically there are only 9 families, with species of nowadays Ascorhynchidae placed under Ammotheidae and Pallenopsidae under Callipallenidae. Both were eventually separated after they are considered distinct from the once-belonged families.<ref name=":8" />

Phylogenomic analysis of extant sea spiders was able to establish a backbone tree for Pantopoda, revealing some consistent relationship such as the basal position of [[Austrodecidae]], [[monophyly]] of some major branches (later redefined as superfamilies<ref name=":14">{{Cite journal |last1=Sabroux |first1=Romain |last2=Corbari |first2=Laure |last3=Hassanin |first3=Alexandre |date=2023-05-01 |title=Phylogeny of sea spiders (Arthropoda: Pycnogonida) inferred from mitochondrial genome and 18S ribosomal RNA gene sequences |url=https://www.sciencedirect.com/science/article/abs/pii/S105579032300026X |journal=Molecular Phylogenetics and Evolution |volume=182 |pages=107726 |doi=10.1016/j.ympev.2023.107726 |bibcode=2023MolPE.18207726S |issn=1055-7903}}</ref>) and the [[paraphyly]] of [[Callipallenidae]] in respect to [[Nymphonidae]].<ref name=":8" /><ref>{{Cite journal |last=Hassanin |first=Alexandre |date=2010-01-01 |title=Studying Sources of Incongruence In Arthropod Molecular Phylogenies: Sea Spiders (Pycnogonida) As a Case Study |url=https://www.academia.edu/458876 |journal=Comptes Rendus Biologies}}</ref><ref name=":0">{{Cite journal |last1=Ballesteros |first1=Jesús A |last2=Setton |first2=Emily V W |last3=Santibáñez-López |first3=Carlos E |last4=Arango |first4=Claudia P |last5=Brenneis |first5=Georg |last6=Brix |first6=Saskia |last7=Corbett |first7=Kevin F |last8=Cano-Sánchez |first8=Esperanza |last9=Dandouch |first9=Merai |last10=Dilly |first10=Geoffrey F |last11=Eleaume |first11=Marc P |last12=Gainett |first12=Guilherme |last13=Gallut |first13=Cyril |last14=McAtee |first14=Sean |last15=McIntyre |first15=Lauren |date=2021-01-23 |editor-last=Crandall |editor-first=Keith |title=Phylogenomic Resolution of Sea Spider Diversification through Integration of Multiple Data Classes |url=https://academic.oup.com/mbe/article/38/2/686/5904272 |journal=Molecular Biology and Evolution |language=en |volume=38 |issue=2 |pages=686–701 |doi=10.1093/molbev/msaa228 |issn=1537-1719 |pmc=7826184 |pmid=32915961}}</ref> The topology also suggest Pantopoda undergoing [[convergent evolution|multiple times]] of cephalic appendage reduction/reappearance and polymerous species acquisition, contray to previous hypothesis on pantopod evolution (cephalic appendages were thought to be progressively reduced along the branches, and polymerus condition were though to be ancestral).<ref name=":14" /> On the other hand, the position of [[Ascorhynchidae]] and ''[[Nymphonella]]'' are less certain across multiple results.<ref name=":0" /><ref name=":14" />

The position of Paleozoic pycnogonids are poorly examined, but most, if not, all of them most likely represent members of [[stem-group]] basal than Pantopoda ([[crown-group]] Pycnogonida), especially those with segmented abdomen, a feature that was most likely [[Plesiomorphy and symplesiomorphy|ancestral]] and reduce in the Pantopoda lineage.<ref name=":92">{{Cite journal |last1=Bergström |first1=Jan |last2=Stürmer |first2=Wilhelm |last3=Winter |first3=Gerhard |date=1980 |title=''Palaeoisopus'', ''Palaeopantopus'' and ''Palaeothea'', pycnogonid arthropods from the Lower Devonian Hunsriick Slate, West Germany |url=https://www.academia.edu/5146832 |journal=Paläontologische Zeitschrift |volume=54 |issue=1–2 |pages=7 |doi=10.1007/BF02985882 |bibcode=1980PalZ...54....7B |issn=0031-0220}}</ref><ref name=":19" /><ref>{{Cite journal |last1=Kühl |first1=Gabriele |last2=Poschmann |first2=Markus |last3=Rust |first3=Jes |date=2013 |title=A ten-legged sea spider (Arthropoda: Pycnogonida) from the Lower Devonian Hunsrück Slate (Germany) |url=https://www.cambridge.org/core/journals/geological-magazine/article/abs/tenlegged-sea-spider-arthropoda-pycnogonida-from-the-lower-devonian-hunsruck-slate-germany/49C52AA72ABDF4B6E8DF2F572C0D51AE |journal=Geological Magazine |language=en |volume=150 |issue=3 |pages=556–564 |doi=10.1017/S0016756812001033 |bibcode=2013GeoM..150..556K |issn=0016-7568|url-access=subscription }}</ref><ref name=":14" /><ref name=":1" /> While some phylogenetic analysis placing them within Pantopoda, this result is questionable as they have low support values and based on outdated interpretation of the fossil taxa.<ref name=":12" /><ref name=":20">{{Cite journal |last1=Siveter |first1=Derek J. |last2=Sabroux |first2=Romain |last3=Briggs |first3=Derek E. G. |last4=Siveter |first4=David J. |last5=Sutton |first5=Mark D. |date=2023 |title=Newly discovered morphology of the Silurian sea spider ''Haliestes'' and its implications |url=https://onlinelibrary.wiley.com/doi/10.1002/spp2.1528 |journal=Papers in Palaeontology |language=en |volume=9 |issue=5 |doi=10.1002/spp2.1528 |bibcode=2023PPal....9E1528S |issn=2056-2799|hdl=1983/267d44cb-bd22-4a1d-9d00-b3916c453784 |hdl-access=free }}</ref><ref name=":15">{{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>

According to the [[World Register of Marine Species]], the Class Pycnogonida is subdivided as follows<ref>{{Cite web |title=WoRMS - World Register of Marine Species - Pycnogonida |url=https://marinespecies.org/aphia.php?p=taxdetails&id=1302 |access-date=2024-12-15 |website=marinespecies.org}}</ref> (with subsequent updates on fossil taxa after Sabroux et al. (2023,<ref name=":13" /> 2024<ref name=":1" />)):

*Genus †''[[Cambropycnogon]]'' Waloszek & Dunlop, 2002<ref name=":18" />
*Genus †''[[Flagellopantopus]]'' Poschmann & Dunlop, 2005 (classified under Pantopoda ''incertae sedis'' by WoRMS<ref name=":23" />)
*Genus †''[[Haliestes]]'' Siveter et al., 2004 (previously classified under Order Nectopantpoda Bamber, 2007 and Family Haliestidae Bamber, 2007)
*Genus †''[[Palaeoisopus]]'' Broili, 1928 (Previously classified under Order Palaeoisopoda Hedgpeth, 1978 and Family Palaeoisopodidae Dubinin, 1957)
*Genus †''[[Palaeomarachne]]'' Rudkin et al., 2013
*Genus †''[[Palaeopantopus]]'' Broili, 1929 (Previously classified under Order Palaeopantopoda Broili, 1930 and Family Palaeopantopodidae Hedgpeth, 1955)
* Genus †''[[Palaeothea]]'' Bergstrom, Sturmer & Winter, 1980 (previously classified under Pantopoda, potential ''[[nomen dubium]]'')
* Genus †''[[Pentapantopus]]'' Kühl, Poschmann & Rust, 2013 (previously classified under Pantopoda)
*Order Pantopoda Gerstäcker, 1863<ref>{{Cite web |title=WoRMS - World Register of Marine Species - Pantopoda |url=https://marinespecies.org/aphia.php?p=taxdetails&id=1358 |access-date=2024-12-15 |website=marinespecies.org}}</ref>
**Suborder [[Eupantopodida]] Fry, 1978<ref>{{Cite web |title=WoRMS - World Register of Marine Species - Eupantopodida |url=https://marinespecies.org/aphia.php?p=taxdetails&id=379601 |access-date=2024-12-15 |website=marinespecies.org}}</ref>
***Superfamily [[Ammotheoidea]] Dohrn, 1881
****Family [[Ammotheidae]] Dohrn, 1881
****Family [[Pallenopsidae]] Fry, 1978
***Superfamily [[Ascorhynchoidea]] Pocock, 1904
****Family [[Ascorhynchidae]] Hoek, 1881 (=Eurycydidae Sars, 1891)
***Superfamily [[Colossendeoidea]] Hoek, 1881 (=Pycnogonoidea Pocock, 1904; Rhynchothoracoidea Fry, 1978)
****Family [[Colossendeidae]] Jarzynsky, 1870
****Family [[Pycnogonidae]] Wilson, 1878
****Family [[Rhynchothoracidae]] Thompson, 1909
***Superfamily [[Nymphonoidea]] Pocock, 1904
****Family [[Callipallenidae]] Hilton, 1942
****Family [[Nymphonidae]] Wilson, 1878
***Superfamily [[Phoxichilidioidea]] Sars, 1891
****Family [[Endeidae]] Norman, 1908
****Family [[Phoxichilidiidae]] Sars, 1891
**Suborder [[Stiripasterida]] Fry, 1978<ref>{{Cite web |title=WoRMS - World Register of Marine Species - Stiripasterida |url=https://marinespecies.org/aphia.php?p=taxdetails&id=379600 |access-date=2024-12-05 |website=marinespecies.org}}</ref>
***Family [[Austrodecidae]] Stock, 1954
**Suborder ''incertae sedis''<ref name=":23">{{Cite web |title=WoRMS - World Register of Marine Species - Pantopoda ''incertae sedis'' |url=https://marinespecies.org/aphia.php?p=taxdetails&id=150518 |access-date=2024-12-15 |website=marinespecies.org}}</ref>
*** Family †[[Palaeopycnogonididae]] Sabroux, Edgecombe, Pisani & Garwood, 2023
***Genus ''[[Alcynous]]'' Costa, 1861 (nomen dubium)
***Genus ''[[Foxichilus]]'' Costa, 1836 (nomen dubium)
***Genus ''[[Oiceobathys]]'' Hesse, 1867 (nomen dubium)
***Genus ''[[Oomerus]]'' Hesse, 1874 (nomen dubium)
***Genus ''[[Paritoca]]'' Philippi, 1842 (nomen dubium)
***Genus ''[[Pephredro]]'' Goodsir, 1842 (nomen dubium)
***Genus ''[[Phanodemus]]'' Costa, 1836 (nomen dubium)
***Genus ''[[Platychelus]]'' Costa, 1861 (nomen dubium)