Schizomida

Taxobox
name = Schizomida


image_caption = Schizomid dorsal scheme
regnum = Animalia
phylum = Arthropoda
subphylum = Chelicerata
classis = Arachnida
ordo = Schizomida
ordo_authority = Petrunkevitch, 1945b
subdivision_ranks = Families
subdivision =
Calcitronidae † Petrunkevitch, 1945b
Hubbardiidae Cook, 1899
Protoschizomidae Rowland, 1975

Schizomida is an order of arachnids, superficially resembling spiders and generally less than 5mm in length.

The order is not yet widely studied. As of 2005, more than 230 species of schizomids have been described worldwide, most belonging to the Hubbardiidae family. A systematic review including a full catalogue may be found in Reddell & Cokendolpher (1995).

Anatomy

In schizomids, the prosoma (cephalothorax) is covered by a large protopeltidium and smaller, paired, mesopeltidia and metapeltidia. The name means "split or cleaved middle", referring to the way the thorax is divided into two separate plates. There are no eyes.

The opisthosoma (abdomen) is a smooth oval of 12 recognizable somites. The first is reduced and forms the pedicel. The last three are much constricted, forming the pygidium. The last somite bears the whip-like tail or flagellum, which in this order is short and consists of not more than four segments.

Like the related orders Uropygi, Amblypygi, and Solifugae, the schizomids use only six legs for walking, having modified their first two legs to serve as sensory organs. They also have large well-developed pedipalps (pincers) just behind the sensory legs.

Habitat

Schizomids are generally tropical creatures, although some populations have been found in California and Arizona. They tend to live in the top layer of soil and in the cavities beneath logs and rocks, where they can avoid desiccation. They seek water and avoid light. Some species are troglobites (cave-dwellers), and a few live in or near termite or ant colonies.

ubtaxa

Schizomids are grouped into three families:
* Calcitronidae † (fossil)
* Hubbardiidae
* Protoschizomidae

References

* Reddell, J.R. & Cokendolpher, J.C. (1995). Catalogue, bibliography, and generic revision of the order Schizomida (Arachnida). Tex. Mem. Mus., Speleol. Monogr. 4: 1-170
* Savory, T., 1977. Arachnida. second edition. Academic Press inc. New York. 339pp.