Arachnomorpha

{{Automatic taxobox

| image = Bellacartwrightia calliteles lateraloblique CRF.jpg

| image_caption = Fossil of Bellacartwrightia calliteles, a trilobite

| image2 = Lychas variatus 239300085.jpg

| image2_caption = Lychas variatus, a scorpion chelicerate

| fossil_range = {{fossil range|538.8|0|Cambrian - Recent}}

| taxon = Arachnomorpha

| authority = Lameere, 1890

| subdivision_ranks = Subgroups

| subdivision = *{{extinct}}Artiopoda

{{extinct}}Megacheira
?{{extinct}}Marrellomorpha
Chelicerata

| synonyms = *Arachnata Paulus, 1979

Palaeopoda Packard, 1903

}}

Arachnomorpha is a proposed subdivision or clade of Arthropoda, comprising the group formed by the trilobites and their close relatives (Artiopoda), Megacheira (which may be paraphyletic) and chelicerates. Under this proposed classification scheme, Arachnomorpha is considered the sister group to Mandibulata (including insects, crustaceans and myriapods).{{Cite journal |last=Aria |first=Cédric |date=2022-04-26 |title=The origin and early evolution of arthropods |journal=Biological Reviews |volume=97 |issue=5 |language=en |pages=1786–1809 |doi=10.1111/brv.12864 |pmid=35475316 |s2cid=243269510 |issn=1464-7931|url=http://paleorxiv.org/4zmey/ }}

The arachnomorph concept has been challenged by suggestions that the artiopods are more closely related to mandibulates, forming the clade Antennulata instead.{{cite book|author = Gerhard Scholtz|author2 = Gregory Edgecombe|name-list-style = amp| year = 2005| chapter = Heads, Hox and the phylogenetic position of trilobites| citeseerx = 10.1.1.130.2585| title = Crustacea and Arthropod Relationships| pages = 139–165| publisher = CRC Press}}

There is no consensus as to assigning Arachnomorpha a formal Linnean rank.

Classification

Arachnomorpha Lameere, 1890 [= Arachnata Paulus, 1979, = Palaeopoda Packard, 1903]

†Nettapezoura
†Dicranocaris
†Trilobita Walch, 1771
†Megacheira Hou & Bergstrom, 1997
†Strabopida Hou & Bergström, 1997
†Aglaspida Walcott, 1911
†Cheloniellida Broili, 1932
Chelicerata Heymons 1901
Family †Sanctacarididae Legg & Pates, 2017
Class Pycnogonida Latreille, 1810
Clade Euchelicerata Weygoldt & Paulus, 1979
Family †Offacolidae Sutton et al., 2002
Clade Prosomapoda Lamsdell, 2013

=Phylogeny=

Using fossil data, Bergström & Hou (2003) gave an outline of arthropod relationships emphasizing trilobitomorphs (a group that includes trilobites and trilobite-like animals).{{cite journal|author= Bergström, J.|author2= Hou, X. G.|name-list-style= amp|year= 2003|title= Arthropod origins|journal= Bulletin of Geosciences|volume= 78|issue= 4|pages= 323–334|url= http://mzp.cz/ris/ekodisk-new.nsf/1a76d1df1a0e29f0c1256e2800520b9d/9a21746463a798e9c125708f002d7766/$FILE/str.%20323-334.pdf|access-date= 2014-03-03|archive-url= https://web.archive.org/web/20160304023625/http://www.mzp.cz/ris/ekodisk-new.nsf/1a76d1df1a0e29f0c1256e2800520b9d/9a21746463a798e9c125708f002d7766/$FILE/str.%20323-334.pdf|archive-date= 2016-03-04|url-status= dead}}

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|1={{clade

|label1=Arthropods

|1={{clade

|label1=Arachnomorpha

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|1={{clade

|label1=Limulavida

|1=Sidneyia

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