Pseudoscorpions, also known as false scorpions or book scorpions, are small, scorpion-like arachnids belonging to the order Pseudoscorpiones, also known as Pseudoscorpionida or Chelonethida.
Pseudoscorpion
Phoretic pseudoscorpion (Lamprochernes sp.) on a fly, Germany
A book scorpion (Chelifer cancroides) on top of an open book
Example of pseudoscorpions preserved in amber. (a) Progonatemnus succineus, (b) Roncus succineus, (c) Chelignathus kochii, (d) Neobisium exstinctum, (e) Electrochelifer balticus, (f) Cheiridium hartmanni, (g) Geogarypus macrodactylus, (h) Microcreagris koellneri
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.
"Arachnida" from Ernst Haeckel's Kunstformen der Natur, 1904
Courtship behavior of Thelyphonus sp.
Hubbardia pentapeltis (Schizomida)
Fossil Goniotarbus angulatus (Phalangiotarbida)