Arachnida

Fossil specimens of Sternarthron zitteli, from Delclòs et al. (2008).


Belongs within: Euarthropoda.
Contains: Pseudoscorpiones, Scorpiones, Phalangiotarbida, Opiliones, Ricinulei, Parasitiformes, Solifugae, Acariformes, Trigonotarbida, Tetrapulmonata, Eukoeneniidae.

The Arachnida are a diverse group of mostly terrestrial arthropods, including spiders, mites, scorpions and related taxa. The monophyly of the group relative to other chelicerates has been subject to some debate, with some authors suggesting that 'arachnid' characters may represent convergent adaptations to terrestriality. Relationships within the Arachnida are similarly contentious with a wide array of arrangements having been proposed at one time or another, few of them strongly supported. A relationship between the Tetrapulmonata (including spiders and whip scorpions) and the fossil Trigonotarbida is supported by features including cheliceral structure, presence of a megoperculum, and booklungs on the genital and first post-genital somites (Shultz 2007). A relationship between Pseudoscorpiones and Solifugae (forming a clade 'Haplocnemata') has been suggested on the basis of cheliceral morphology (Shultz 2007) but has been refuted by recent analyses.

Particularly hard to place are the Palpigradi, a group of minute, segmented arachnids with with an elongate abdomen terminating in a whip-like, seta-bearing flagellum. Palpigrades inhabit damp habitats such as soil or leaf litter with members of the genus Leptokoenenia inhabiting interstitial habitats along shorelines. The Jurassic fossil Sternarthron zitteli has been assigned to the Palpigradi but is considerably larger than any living species and may be misplaced (Harvey 2002).

The mites are a diverse assemblage of mostly very small arachnids commonly treated as a formal group Acari or Acarina. Mites have been divided between two major lineages: the Acariformes have birefringent setae with a core of actinopilin whereas the Parasitiformes (or Anactinotrichida) lack such setae. Whether the mites as a whole represent a monophyletic group remains a contested issue. Mite larvae have only six walking legs when they first emerge, with the fourth pair developing in later instars. This feature is shared with the Ricinulei, leading some authors to suggest a relationship between mites and ricinuleids, but other analyses have placed the groups separately. Some recent analyses (e.g. Garwood & Dunlop 2014) have supported a relationship between Acariformes and the Solifugae (camel spiders); potential shared characters of these two groups include the presence of a sejugal furrow between the second and third coxae.

Synapomorphies (from Shultz 2007): Carapacal pleural doublure absent; cardiac lobe absent; coxal gnathobases absent; coxae lacking moveable endites; aerial respiration; mouth directed anteroventrally.

Arachnida (see below for synonymy)
    |--+--+--+--Pseudoscorpiones GD16
    |  |  |  `--Scorpiones GD16
    |  |  `--+--Phalangiotarbida GD16
    |  |     `--Opiliones GD16
    |  `--+--+--Ricinulei GD16
    |     |  `--+--Parasitiformes GD16
    |     |     `--Poecilophysidea GD14
    |     |          |--Solifugae SF15
    |     |          `--Acariformes GD14
    |     `--Pantetrapulmonata GD14
    |          |  i. s.: Ecchosis pulchribothrium Selden & Shear 1991 S93
    |          |--Trigonotarbida GD16
    |          |--Tetrapulmonata GD16
    |          `--Mesotarbus LSE13
    |               |--M. angustus (Pocock 1911) S93
    |               |--M. eggintoni (Pocock 1911) S93
    |               |--M. hindi S93
    |               `--M. intermedius Petrunkevitch 1949 S93
    `--Palpigradi [Microteliphonida] GD14
         |  i. s.: Triadokoenenia HST06
         |         Allokoenenia afra Silvestri 1913 HST06
         |         Leptokoenenia M86
         |           |--L. gerlachi Condé 1965 M86
         |           `--L. scurra Monniot 1966 M86
         |         Koeneniodes HST06
         |           |--K. berndi Condé 1988 HST06
         |           |--K. deharvengi HST06
         |           |--K. frondiger Rémy 1950 HST06
         |           |--K. leclerci HST06
         |           |--K. madecassus Rémy 1950 HST06
         |           |--K. malagasorum Rémy 1960 HST06
         |           |--K. notabilis HST06
         |           `--K. spiniger HST06
         |--Prokoenenia [Prokoeneniidae] HST06
         |    `--P. wheeleri GE02
         |--Sternarthron Haase 1890 H02 [Sternarthronidae S93]
         |    `--*S. zitteli Haase 1890 H02
         `--Eukoeneniidae S93

Arachnida incertae sedis:
  Enyo E12
    |--E. algirica Lucas 1846 E12
    `--E. amaranthina Lucas 1846 E12
  Cyrtocephalus Lucas 1846 E12
    |--C. terricola Lucas 1846 E12
    `--C. walckenaerii Lucas 1846 E12
  Monastes Lucas 1846 E12
    |--M. lapidarius Lucas 1846 E12
    `--M. paradoxus Lucas 1846 E12
  Hemialges F54
  Falculifera echinopus F54
  Hygrochoreutes krameri BK91
  Panisopsis thori (Walter 1907) GS91
  Tenuipalponychus citri G91
  Beerella depicta W99
  Sonotetranychus albiflorae W99
  Pachylichus Canestrini 1894 [=Pachylicus (l. c.) non Roewer 1923] KA-Z11
  Fonsecia ptyasi Rao & Hiregander 1959 S69
  Hoshikadania Sasa & Asanuma 1951 S94
  Trichadenus Rondani 1870 CF77
  Crocidurobia michaeli GHG91
  Tapinattus melanognathus (see below for synonymy) S99
  Melanophora S99
    |--M. flavens S99
    |--M. pacifica Simon 1899 S99
    `--M. rustica S99

Arachnida [Acari, Acarida, Acarina, Acarinomorpha, Acaromorpha, Actinochaeta, Actinoderma, Apatellata, Apulmonata, Arachnopulmonata, Arthrogastra, Chelodonta, Cryptognomae, Cryptoperculata, Dromopoda, Epimerata, Galeodides, Haplocnemata, Holotracheata, Lipoctena, Meridogastra, Micrura, Neosternata, Novogenuata, Obisides, Pedipalpata, Phalangiata, Riciniae, Rostrosomata, Scorpionides, Solenostoma, Solpugae, Sternocoxata, Stomothecata]

Tapinattus melanognathus [=Attus melanognathus; incl. Salticus convergens Doleschall 1859, Marpissa dissimilis Koch 1846, M. incerta Koch 1846, Attus muscivorus Vinson 1864, Salticus nigrolimbatus Cambr. 1869] S99

*Type species of generic name indicated

REFERENCES

[BK91] Biesiadka, E., & W. Kowalik. 1991. Water mites (Hydracarina) as indicators of trophy and pollution in lakes. In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 1 pp. 475–481. SPB Academic Publishing: The Hague.

[CF77] Canestrini, G., & F. Fanzago. 1877. Intorno agli Acari Italiani. Atti del Reale Istituto Veneto di Scienze, Lettere ed Arti, Serie 5, 4: 69–208, pls 2–7.

[E12] Evenhuis, N. L. 2012. Publication and dating of the Exploration Scientifique de l'Algérie: Histoire Naturelle des Animaux Articulés (1846–1849) by Pierre Hippolyte Lucas. Zootaxa 3448: 1–61.

[F54] Forster, R. R. 1954. The New Zealand harvestmen (sub-order Laniatores). Canterbury Museum Bulletin 2: 1–329.

[GHG91] Gállego, M., E. Hidalgo & J. Ginés. 1991. Mites of the house mouse, Mus musculus L., in the north-eastern part of the Iberian Peninsula in Spain. In: Schuster, R., & P. W. Murphy (eds) The Acari: Reproduction, development and life-history strategies pp. 453–454. Chapman & Hall: London.

[GD14] Garwood, R. J., & J. Dunlop. 2014. Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders. PeerJ 2: e641.

[GD16] Garwood, R. J., J. A. Dunlop, P. A. Selden, A. R. T. Spencer, R. C. Atwood, N. T. Vo & M. Drakopoulos. 2016. Almost a spider: a 305-million-year-old fossil arachnid and spider origins. Proceedings of the Royal Society of London Series B—Biological Sciences 283: 20160125.

[GS91] Gerecke, R., & J. Schwoerbel. 1991. Water quality and water mites (Acari, Actinedida) in the Upper Danube region, 1959–1984. In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 1 pp. 483–491. SPB Academic Publishing: The Hague.

[GE02] Giribet, G., G. D. Edgecombe, W. C. Wheeler & C. Babbitt. 2002. Phylogeny and systematic position of Opiliones: a combined analysis of chelicerate relationships using morphological and molecular data. Cladistics 18: 5–70.

[G91] Gupta, S. K. 1991. The mites of agricultural importance in India with remarks on their economic status. In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 1 pp. 509–522. SPB Academic Publishing: The Hague.

[H02] Harvey, M. S. 2002. The neglected cousins: what do we know about the smaller arachnid orders? Journal of Arachnology 30 (2): 357–372.

[HST06] Harvey, M. S., F. Štáhlavský & P. D. Theron. 2006. The distribution of Eukoenenia mirabilis (Palpigradi: Eukoeneniidae): a widespread tramp. Records of the Western Australian Museum 23 (2): 199–203.

[KA-Z11] Kury, A. B., & M. A. Alonso-Zarazaga. 2011. Addenda and corrigenda to the "Annotated catalogue of the Laniatores of the New World (Arachnida, Opiliones)". Zootaxa 3034: 47–68.

[LSE13] Legg, D. A., M. D. Sutton & G. D. Edgecombe. 2013. Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature Communications 4: 2485.

[M86] Monniot, F. 1986. Palpigradi. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) p. 697. E. J. Brill/Dr W. Backhuys: Leiden.

[S93] Selden, P. A. 1993. Arthropoda (Aglaspidida, Pycnogonida and Chelicerata). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 297–320. Chapman & Hall: London.

[SF15] Sharma, P. P., R. Fernández, L. A. Esposito, E. González-Santillán & L. Monod. 2015. Phylogenomic resolution of scorpions reveals multilevel discordance with morphological phylogenetic signal. Proceedings of the Royal Society of London Series B—Biological Sciences 282: 20142953.

Shultz, J. W. 2007. A phylogenetic analysis of the arachnid orders based on morphological characters. Zoological Journal of the Linnean Society 150 (2): 221–265.

[S99] Simon, E. 1899. Ergebnisse einer Reise nach dem Pacific (Schauinsland 1896–1897. Zoologische Jahrbücher, Abteilung für Systematik, Geographie un Biologie der Thiere 12 (4): 411–437.

[S94] Southcott, R. V. 1994. Revision of the larvae of the Microtrombidiinae (Acarina, Microtrombidiidae), with notes on life histories. Zoologica 48 (2): 1–155.

[S69] Steyskal, G. C. 1969. The mistreatment of the Latin genitive case in forming names of parasites. Systematic Zoology 18 (3): 339–342.

[W99] Walter, D. E. 1999. Cryptic inhabitants of a noxious weed: mites (Arachnida: Acari) on Lantana camara L. invading forests in Queensland. Australian Journal of Entomology 38: 197–200.

Last updated: 21 May 2019.

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