Harvestman phylogeny

In 1990, Shultz proposed grouping them with scorpions, pseudoscorpions and Solifugae ("camel spiders"); he named this clade Dromopoda.

Analyses of recent taxa suggested the harvestmen to be the sister group of the three others, collectively called Novogenuata.

[3] Recent analyses have also recovered the Opiliones as sister-group to the extinct Phalangiotarbids,[4][5] although this has low support, or as sister group to a pseudoscorpion and scorpion clade.

[6][7] In 1796, Pierre André Latreille erected the family "Phalangida" [sic] for the then known harvestmen, but included the genus Galeodes (Solifugae).

Opiliones' own divergence is dated to 414 million years ago, which arachnid are estimated to have originated during the late Cambrian to early Ordivician.

Garwood et al. also argue that Carboniferous harvestmen diversification is more consistent with changes observed in other terrestrial arthropods, which have been linked to high oxygen levels during that period.

[10] The Cyphophthalmi have been divided into two infraorders, Temperophthalmi (including the superfamily Sironoidea, with the families Sironidae, Troglosironidae and Pettalidae) and Tropicophthalmi (with the superfamilies Stylocelloidea and its single family Stylocellidae, and Ogoveoidea, including Ogoveidae and Neogoveidae); however, recent studies suggest that the Sironidae, Neogoveidae and Ogoveidae are not monophyletic, while the Pettalidae and Stylocellidae are.

The relationship of the superfamily Ischyropsalidoidea, comprising the families Ceratolasmatidae, Ischyropsalididae and Sabaconidae, has been investigated in detail.

It is not clear whether Ceratolasmatidae and Sabaconidae are each monophyletic, as the ceratolasmatid Hesperonemastoma groups with the sabaconid Taracus in molecular analyses.

Molecular analyses relying on nuclear ribosomal genes support monophyly of Gonyleptidae, Cosmetidae (both Gonyleptoidea), Stygnopsidae (currently Assamioidea) and Phalangodidae.

The families of the obsolete Assamioidea have been moved to other groups: Assamiidae and Stygnopsidae are now Gonyleptoidea, Epedanidae reside within their own superfamily Epedanoidea, and the "Pyramidopidae" are possibly related to Phalangodidae.