File:Opiliones sp.at Mechode Padur.jpg

English: Opiliones (/ˈoʊpɪliːˈoʊniːs/; formerly Phalangida) is an order of arachnids commonly known as harvestmen. As of December 2011, over 6,500 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 the recently named Tetrophthalmi.[3] With the exception of Dyspnoi (which is restricted to North America and Eurasia), representatives of each can be found on every continent 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, which look surprisingly modern, indicating that their basic body plan appeared very early on,[4] and, at least in some taxa, has changed little since that time. Their phylogenetic position within Arachnida is disputed: their closest relatives may be the mites (Acari) or the Novogenuata (the Scorpiones, Pseudoscorpiones and Solifugae).[5] Although superficially similar to and often confused with spiders (order Araneae), Opiliones is a distinct order that is not closely related to spiders within Arachnida. They can be easily distinguished from even long-legged spiders by their fused body regions and single pair of eyes in the middle of their cephalothorax (spiders have an 'abdomen' that is separated from the cephalothorax by a constriction, as well as three to four pairs of eyes, usually around the margins of their cephalothorax).