Editing Mygalomorphae (section)

===Evolution===
[[Image:Sphodros rufines.JPG|thumb|''[[Sphodros rufipes]]'', an [[Atypidae|atypical mygalomorph]]]]

''[[Megarachne servinei]]'' was thought to be a giant mygalomorph from the [[Upper Carboniferous]] (about 350&nbsp;million years ago), but was later found to be a [[eurypterid]].<ref name=SeldCorrHuni05/> The oldest known mygalomorph is ''[[Rosamygale grauvogeli]]'' , an avicularoid from the [[Triassic]] of northeastern France. No mygalomorphs from the [[Jurassic]] have yet been found.<ref name=SeldDacoVian05/>

The number of families and their relationships have both been undergoing substantial changes since a cladogram showing family relationships was published in 2005,<ref name=Codd05/> with two significant studies in 2018.<ref name=HediDerkRamiVink18/><ref name=GodwOpatGarrHami18/> The division of Mygalomorphae into two superfamilies, [[Atypoidea]] and [[Avicularioidea]], has been established in many studies. The Atypoidea retain some vestiges of abdominal segmentation in the form of dorsal [[Tergum|tergite]]s; the Avicularioidea lack these. [[Molecular phylogeny|Molecular phylogenetic]] studies undertaken between 2012 and 2017 have found somewhat different relationships within the Avicularioidea. Some families appear not to be [[Monophyly|monophyletic]] and further changes are possible in the future.<ref name=WheeCoddCrowDimi16/> ''Rosamygale'' belongs to Avicularioidea, based on the absence of an abdominal [[Glossary of spider terms#S|scutum]] and well-separated posterior lateral spinnerets.<ref name=":0">{{cite journal |last1=Magalhaes |first1=Ivan L.F. |last2=Azevedo |first2=Guilherme H.F. |last3=Michalik |first3=Peter |last4=Ramírez |first4=Martín J. |year=2020 |title=The fossil record of spiders revisited: Implications for calibrating trees and evidence for a major faunal turnover since the Mesozoic |journal=Biological Reviews |volume=95 |issue=1 |pages=184–217 |doi=10.1111/brv.12559 |pmid=31713947 |s2cid=207937170 |issn=1464-7931 |language=en |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/brv.12559|url-access=subscription }}</ref>

Mygalomorphae tend to be highly morphologically conserved, which makes it difficult to find reliable morphological features to use for taxonomy. It has been hypothesized that because Mygalomorphae all tend to be [[fossorial]] and live in tubular webs, they are subjected to similar selective pressures, so most species should evolve in similar ways. Additionally, this may also mean that [[Homoplasy|homoplasies]] are more likely to occur, further complicating taxonomy based on morphology.<ref>{{cite journal |last1=Bond |first1=Jason E. |last2=Hedin |first2=Marshal |date=2006-10-01 |title=A total evidence assessment of the phylogeny of North American euctenizine trapdoor spiders (Araneae, Mygalomorphae, Cyrtaucheniidae) using Bayesian inference |journal=Molecular Phylogenetics and Evolution |volume=41 |issue=1 |pages=70–85 |doi=10.1016/j.ympev.2006.04.026 |issn=1055-7903 |pmid=16857391 |bibcode=2006MolPE..41...70B |language=en |url=http://www.sciencedirect.com/science/article/pii/S1055790306001722|url-access=subscription }}</ref>