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Opiliones

For other arthropods called "daddy longlegs", and other uses, see Daddy longlegs (disambiguation). For the novel by Jean Webster, see Daddy-Long-Legs (novel).

Opiliones
Temporal range: Early Devonian – Holocene
Hadrobunus grandis showing its body structure and long legs: one pair of eyes and broadly joined body tagma differentiate it from similar-looking arachnids.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Opiliones
Sundevall, 1833
Suborders
Diversity
5 suborders, > 6,650 species

The Opiliones (formerly Phalangida) are an order of arachnids colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs. As of April 2017, over 6,650 species of harvestmen have been discovered worldwide,[1] although the total number of extant species may exceed 10,000.[2] The order Opiliones includes five suborders: Cyphophthalmi, Eupnoi, Dyspnoi, Laniatores, and Tetrophthalmi, which were named in 2014.[3]

Representatives of each extant suborder can be found on all continents except Antarctica.

Well-preserved fossils have been found in the 400-million-year-old Rhynie cherts of Scotland, and 305-million-year-old rocks in France. These fossils look surprisingly modern, indicating that their basic body shape developed very early on,[4] and, at least in some taxa, has changed little since that time.

Their phylogenetic position within the Arachnida is disputed; their closest relatives may be camel spiders (Solifugae) or a larger clade comprising horseshoe crabs, Ricinulei, and Arachnopulmonata (scorpions, pseudoscorpions, and Tetrapulmonata).[5][6] Although superficially similar to and often misidentified as spiders (order Araneae), the Opiliones are a distinct order that is not closely related to spiders. They can be easily distinguished from long-legged spiders by their fused body regions and single pair of eyes in the middle of the cephalothorax. Spiders have a distinct abdomen that is separated from the cephalothorax by a constriction, and they have three to four pairs of eyes, usually around the margins of the cephalothorax.

English speakers may colloquially refer to species of Opiliones as "daddy longlegs" or "granddaddy longlegs", but this name is also used for two other distantly related groups of arthropods, the crane flies of the superfamily Tipuloidea, and the cellar spiders of the family Pholcidae, (commonly referred to as "daddy long-leg spiders") most likely because of their similar appearance. Harvestmen are also referred to as "shepherd spiders" in reference to how their unusually long legs reminded observers of the ways that some European shepherds used stilts to better observe their wandering flocks from a distance.[7]

  1. ^ Kury, Adriano B. "Classification of Opiliones". www.museunacional.ufrj.br. Retrieved 2017-11-29.
  2. ^ Glauco Machado, Ricardo Pinto-da-Rocha & Gonzalo Giribet (2007). "What are harvestmen?". In Ricardo Pinto-da-Rocha, Glauco Machado & Gonzalo Giribet (ed.). Harvestmen: the Biology of Opiliones. Harvard University Press. pp. 1–13. ISBN 978-0-674-02343-7.
  3. ^ Cite error: The named reference Tetro was invoked but never defined (see the help page).
  4. ^ Garwood, Russell J.; Dunlop, Jason A.; Giribet, Gonzalo; Sutton, Mark D. (2011). "Anatomically modern Carboniferous harvestmen demonstrate early cladogenesis and stasis in Opiliones". Nature Communications. 2: 444. Bibcode:2011NatCo...2..444G. doi:10.1038/ncomms1458. PMID 21863011.
  5. ^ Ballesteros, Jesús A; Sharma, Prashant P (2019-11-01). Halanych, Ken (ed.). "A Critical Appraisal of the Placement of Xiphosura (Chelicerata) with Account of Known Sources of Phylogenetic Error". Systematic Biology. 68 (6): 896–917. doi:10.1093/sysbio/syz011. ISSN 1063-5157. PMID 30917194.
  6. ^ Ballesteros, Jesús A; Santibáñez-López, Carlos E; Baker, Caitlin M; Benavides, Ligia R; Cunha, Tauana J; Gainett, Guilherme; Ontano, Andrew Z; Setton, Emily V W; Arango, Claudia P; Gavish-Regev, Efrat; Harvey, Mark S; Wheeler, Ward C; Hormiga, Gustavo; Giribet, Gonzalo; Sharma, Prashant P (2022-02-03). Teeling, Emma (ed.). "Comprehensive Species Sampling and Sophisticated Algorithmic Approaches Refute the Monophyly of Arachnida". Molecular Biology and Evolution. 39 (2). doi:10.1093/molbev/msac021. ISSN 0737-4038. PMC 8845124. PMID 35137183.
  7. ^ Joyce Tavolacci, ed. (2003), Insects and spiders of the world, vol. 5: Harvester ant to leaf-cutting ant, Marshall Cavendish, p. 263, ISBN 978-0-7614-7334-3
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