Микроскорпионы-хлыстики: описание и распространение

Order of arachnids known as microwhip scorpions

Palpigradi is an order of very small arachnids commonly known as microwhip scorpion or palpigrades.

Palpigrades belong to the arachnid class. no more than in length, They have a thin, pale, segmented integument, and a segmented abdomen that terminates in a whip like flagellum. This is made up of 15 segment like parts, or "articles", and may make up as much as half the animal's length. But they do not swing in phase with the walking legs, and are mostly used as legs in rough terrain. Both the nine segmented pedipalps and the four pairs of legs end in three claws each. The first pair of legs are 11 segmented, the second and third pairs seven segmented and the fourth pair eight segmented. The family Prokoeneniidae have three pairs of lung sacs on the fourth, fifth and sixth abdominal segments, although these are not true book lungs as there is no trace of the characteristic leaflike lamellae which defines book lungs. Family Eukoeneniidae have no respiratory organs at all and breathe directly through the cuticle. Their Exoskeleton is very weakly sclerotized compared to other arachnids, which is the reason why fossils are so rare, and go no further back than 99 million years ago in Burmese Amber.

Species of Palpigradi live interstitially in wet tropical and subtropical soils. In Europe, they have been found in caves and underground spaces. They need a damp environment to survive, and they always hide from light, so they are commonly found in the moist earth under buried stones and rocks. They can be found on every continent, except in Arctic and Antarctic regions. Terrestrial Palpigradi have hydrophobic cuticles, but littoral (beach dwelling) species are able to pass through the water surface easily. Two fossil palpigrade species have been described. The first one is from the Onyx Marble of Arizona, which is probably of Pliocene age. Its familial position is uncertain. The second one (Electrokoenenia yaksha), belonging to the family Eukoeneniidae, is known from Cretaceous (Cenomanian) Burmese amber from northern Myanmar. Older publications refer to a fossil palpigrade (or palpigrade like animal) from the Jurassic of the Solnhofen limestone in Germany, but this has now been shown to be a misidentified fossil insect.