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Opiliones
| Opiliones | |
|---|---|
| |
| 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 
| |
| 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 (see § Etymology below). As of July 2024[update], over 6,650 species of harvestmen have been discovered worldwide,[1][2][3] although the total number of extant species may exceed 10,000.[4] The order Opiliones includes five suborders: Cyphophthalmi, Eupnoi, Dyspnoi, Laniatores, and Tetrophthalmi, which were named in 2014.[5]
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,[6] 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).[7][8] 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.
- ^ Cite error: The named reference
WCO-litewas invoked but never defined (see the help page). - ^ Kury, Adriano B. "Classification of Opiliones". www.museunacional.ufrj.br. Retrieved 2017-11-29.
- ^ Cite error: The named reference
Hallanwas invoked but never defined (see the help page). - ^ 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.
- ^ Cite error: The named reference
Tetrowas invoked but never defined (see the help page). - ^ 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.
- ^ 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.
- ^ 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.
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