Scorpions are predatory arachnids of the order Scorpiones. They have eight legs and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always ending with a stinger. The evolutionary history of scorpions goes back 435 million years. They mainly live in deserts but have adapted to a wide range of environmental conditions, and can be found on all continents except Antarctica. There are over 2,500 described species, with 22 extant (living) families recognized to date. Their taxonomy is being revised to account for 21st-century genomic studies.
Arachnids are arthropods in the class Arachnida of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons.
Amblypygi is an order of arachnids also known as whip spiders or tailless whip scorpions, not to be confused with whip scorpions or vinegaroons that belong to the related order Thelyphonida. The name "amblypygid" means "blunt tail", a reference to a lack of the flagellum that is otherwise seen in whip scorpions. Amblypygids possess no silk glands or venom. They rarely bite if threatened, but can grab fingers with their pedipalps, resulting in thorn-like puncture injuries.
Schizomida, also known as sprickets or short-tailed whip-scorpions, is an order of arachnids, generally less than 5 millimetres (0.20 in) in length. The order is not yet widely studied. E. O. Wilson has identified schizomids as among the "groups of organisms that desperately need experts to work on them."
Uropygi is an arachnid order comprising invertebrates commonly known as whip scorpions or vinegaroons. They are often called uropygids. The name "whip scorpion" refers to their resemblance to true scorpions and possession of a whiplike tail, and "vinegaroon" refers to their ability when attacked to discharge an offensive, vinegar-smelling liquid, which contains acetic acid. The order may also be called Thelyphonida. Both names, Uropygi and Thelyphonida, may be used either in a narrow sense for the order of whip scorpions, or in a broad sense which includes the order Schizomida.
Pedipalps are the secondary pair of forward appendages among chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicerae ("jaws") and anterior to the first pair of walking legs.
Solifugae is an order of animals in the class Arachnida known variously as camel spiders, wind scorpions, sun spiders, or solifuges. The order includes more than 1,000 described species in about 147 genera. Despite the common names, they are neither true scorpions nor true spiders. Most species of Solifugae live in dry climates and feed opportunistically on ground-dwelling arthropods and other small animals. The largest species grow to a length of 12–15 cm (5–6 in), including legs. A number of urban legends exaggerate the size and speed of the Solifugae, and their potential danger to humans, which is negligible.
Tetrapulmonata is a non-ranked supra-ordinal clade of arachnids. It is composed of the extant orders Uropygi, Schizomida, Amblypygi and Araneae (spiders). It is the only supra-ordinal group of arachnids that is strongly supported in molecular phylogenetic studies. Two extinct orders are also placed in this clade, Haptopoda and Uraraneida. In 2016, a newly described fossil arachnid, Idmonarachne, was also included in the Tetrapulmonata; as of March 2016 it has not been assigned to an order.
Mastigoproctus is a genus of whip scorpions. Native to the tropical forest regions of northern South America, these whip scorpions can reach a length of up to 9 centimetres (3.5 in) and can weigh over 30 grams (1.1 oz). Despite popular belief, they are not venomous as, like all other whip scorpions, they do not possess venom glands.
Mastigoproctus colombianus is a whip scorpion species found in Colombia, South America, near west deserts areas.
Afrozomus machadoi is a species of arachnid belonging to the family Hubbardiidae in the order Schizomida, which are commonly known as short-tailed whip scorpions. It is the only identified species in the genus Afrozomus.
Floridobolus is a genus of millipedes commonly known as Florida scrub millipedes containing three described species: Floridobolus penneri, F. orini, and F. floydi; the latter two described in 2014. All three species are endemic to Florida scrub habitat of peninsular Florida, and F. penneri is considered a critically imperiled species by NatureServe. Prior to the description of F. orini, the genus was considered the sole member of the family Floridobolidae, named by William T. Keeton in 1959, however studies in 2014 have argued that Floridobolus does not represent a distinct family but rather is a basal member of the family Spirobolidae, representing the subfamily Floridobolinae, and tribe Floridobolini.
Paraphrynus is a genus of whip spiders, also known as tailless whip scorpions, of the family Phrynidae. It is distributed from the southwestern United States to Central America, including several Caribbean islands. Most species are endemic to Mexico.
Typopeltis is an Asian genus of whip scorpions or 'vinegaroons' and currently the only member of subfamily Typopeltinae.
Tityus trivittatus, commonly known as the Brazilian red house scorpion, is a species of arachnid endemic to South America.
Etienneus is a monotypic genus of Thelyphonid whip scorpions, first described by Jacqueline Heurtault in 1984. Its single species, Etienneusafricanus is distributed in West Africa. It is the only uropygid found in Africa.
Sheylayongium is a monotypic genus of Thelyphonid whip scorpions, first described by Rolando Teruel in 2018. Its single species, Sheylayongium pelegrini is distributed in Cuba.
Geralinura is an extinct genus in the family Thelyphonidae, commonly known as whip scorpions. Fossil evidence found in the midwestern United States and the United Kingdom indicates that this genus lived during the mid-to-late Carboniferous period. Unlike the subchelate pedipalps of modern whip scorpions, the pedipalps of Geralinura are spiked and non-chelate, suggesting that the modern trait evolved at a later point in time.
