Schizomida

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Schizomida
Temporal range: Cenomanian–present
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Hubbardia pentapeltis female.jpg
Female Hubbardia pentapeltis
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Schizomida
Petrunkevitch, 1945
Families

Calcitronidae Petrunkevitch, 1945b
Hubbardiidae Cook, 1899
Protoschizomidae Rowland, 1975

Contents

Schizomida (common name shorttailed whipscorpion) [1] is an order of arachnids, generally less than 5 millimetres (0.20 in) 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). The Schizomida is sister to the order Uropygi, the two clades together forming the Thelyphonida [2] . Based on molecular clock dates, both orders likely originated in the late Carboniferous somewhere in the tropics of Pangea, and the Schizomida underwent substantial diversification starting in the Cretaceous [2] . The oldest known fossil is currently Mesozomus from the Mid-Cretaceous Burmese amber of Myanmar. [3]

Anatomy

Schizomids are relatively big, soft-bodied arachnids, somewhat similar in appearance to whip scorpions. The prosoma (cephalothorax) is divided into three regions, each covered by plates, the large protopeltidium and the smaller, paired, mesopeltidia and metapeltidia. The name means "split or cleaved middle", referring to the way the prosoma is divided into two separate plates. [4]

Modified flagellum of male Hubbardia pentapeltis Hubbardia pentapeltis male flagellum.jpg
Modified flagellum of male Hubbardia pentapeltis

The opisthosoma (abdomen) is a smooth oval of 12 recognizable segments. The first is reduced and forms the pedicel, while the last three are constricted, forming the pygidium. The last segment bears a short whip-like tail or flagellum, consisting of no more than four segments. The females generally have 3-4-segmented flagella, while in males it is single segmented. [5]

Like the related orders Thelyphonida and Amblypygi, and the more distantly related 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 pincer-like pedipalps just before the sensory legs. The hind legs are modified for jumping, as part of their escape response when threatened. [6] Schizomids have no actual eyes, but a few species have vestigial eyespots capable of telling light from dark. They breathe through a single pair of book lungs, as the other pair is lost. [7]

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 cave dwellers, and a few live in or near termite or ant colonies.

Subtaxa

Schizomids are grouped into three families:

Related Research Articles

Arachnid Class of arthropods

Arachnida is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Spiders are the largest order in the class, which also includes scorpions, ticks, mites, harvestmen, and solifuges. In 2019, a molecular phylogenetic study also placed horseshoe crabs in Arachnida.

Amblypygi order of arachnids

Amblypygi is an ancient order of arachnid chelicerate arthropods also known as whip spiders and tailless whip scorpions. The name "amblypygid" means "blunt tail", a reference to a lack of the flagellum that is otherwise seen in whip scorpions. They are harmless to humans. Amblypygids possess no silk glands or venomous fangs. They rarely bite if threatened, but can grab fingers with their pedipalps, resulting in thorn-like puncture injuries.

Opiliones Order of arachnids (harvestmen/daddy longlegs)

The Opiliones are an order of arachnids colloquially known as harvestmen, harvesters, or daddy longlegs. As of April 2017, over 6,650 species of harvestmen have been discovered worldwide, although the total number of extant species may exceed 10,000. The order Opiliones includes five suborders: Cyphophthalmi, Eupnoi, Dyspnoi, Laniatores, and Tetrophthalmi, which were named in 2014.

Palpigradi order of arachnids

Palpigrades, commonly known as microwhip scorpions, are arachnids belonging to the order Palpigradi.

Thelyphonida order of arachnids

Thelyphonida is an arachnid order comprising invertebrates commonly known as whip scorpions or vinegaroons. They are often called uropygids in the scientific community based on an alternative name for the order, Uropygi. The name "whip scorpion" refers to their resemblance to true scorpions and possession of a whiplike tail. "Vinegaroon" is based on their ability when attacked to discharge an offensive liquid which contains acetic acid, producing a vinegar-like smell.

Ricinulei order of arachnids

The order Ricinulei is a group of arachnids known as hooded tickspiders, though they are not true spiders. Like most arachnids, they are predatory, eating small arthropods. In older works they are sometimes referred to as Podogona.

Pedipalp Appendage on front of spider, crab, scorpion

Pedipalps are the second pair of appendages of 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.

<i>Plesiosiro</i> extinct arachnid order

Plesiosiro is an extinct arachnid genus known exclusively from only nine specimens from the Upper Carboniferous of Coseley, Staffordshire, United Kingdom. The genus is monotypic, represented only by the species Plesiosiro madeleyi described by Reginald Innes Pocock in his important 1911 monograph on British Carboniferous arachnids. It is the only known member of the order Haptopoda. The original locality from which these fossils originate is no longer available thus it is unclear whether any further examples will be found.

Tetrapulmonata

Tetrapulmonata is a non-ranked supra-ordinal clade of arachnids. It is composed of the extant orders Thelyphonida, 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.

Draculoides is a genus of troglobite arachnid endemic to North West Australia. Often mistaken for a spider, D. bramstokeri is a schizomid — a small, soil-dwelling invertebrate that walks on six legs and uses two modified front legs as feelers. It uses large fang-like pedipalps, or pincers, to grasp invertebrate prey and crunch it into pieces before sucking out the juices.

Hubbardiidae family of arachnids

Hubbardiidae is a family of arachnids, superficially resembling spiders. It is the larger of the two extant families of the order, Schizomida, and is divided into two subfamilies. The family is based on the description published by Orator F. Cook in 1899, and was previously named as Schizomidae. The American Arachnological Society assigns the common name hubbardiid shorttailed whipscorpion to members of this family

Pacal is a genus of arachnid, belonging to the family Hubbardiidae in the order Schizomida. The genus contains three identified species, all endemic to Mexico.

The family Calcitronidae is an extinct group of arachnids. Its two monotypic genera are only known from Pliocene deposits of calcite in Arizona. The family has been placed in the order Schizomida, but a review of the order concluded that "the fossil taxa ... are so poorly known that final placement must await further study and possibly new material", and they are not listed in the order in a 2016 catalog of fossil arachnids.

Afrozomus machadoi is a species of arachnid, belonging to the family Hubbardiidae in the order Schizomida. It is the only identified species in the genus Afrozomus.

Phrynidae is a family of amblypygid arachnida arthropods also known as whip spiders and tailless whip scorpions. Phrynidae species are found in tropical and subtropical regions in North and South America. Some species are subterranean; all are nocturnal. At least some species of Phrynidae hold territories that they defend from other individuals.

Stenochrus portoricensis is a species of short-tailed whipscorpion in the family Hubbardiidae.

Stenochrus is a genus of short-tailed whipscorpions in the family Hubbardiidae. There are more than 20 described species in Stenochrus.

<i>Hubbardia pentapeltis</i> species of arachnid

Hubbardia pentapeltis is a species of short-tailed whipscorpion in the family Hubbardiidae.

Hubbardia belkini is a species of short-tailed whipscorpion in the family Hubbardiidae.

References

  1. The American Arachnological Society Committee on Common Names of Arachnids (2003). R.G. Breene (chair) (ed.). Common Names of Arachnids 2003 (PDF) (5th ed.). Carlsbad, NM: American Tarantula Society. p. 42. ISBN   1-929427-11-5. Archived from the original (PDF online publication) on 2006-09-27.
  2. 1 2 Clouse, Ronald M.; Branstetter, Michael G.; Buenavente, Perry; Crowley, Louise M.; Czekanski‐Moir, Jesse; General, David Emmanuel M.; Giribet, Gonzalo; Harvey, Mark S.; Janies, Daniel A. (2017). "First global molecular phylogeny and biogeographical analysis of two arachnid orders (Schizomida and Uropygi) supports a tropical Pangean origin and mid-Cretaceous diversification". Journal of Biogeography. 44 (11): 2660–2672. doi:10.1111/jbi.13076. ISSN   1365-2699.
  3. Sandro P. Müller; Jason A. Dunlop; Ulrich Kotthoff; Jörg U. Hammel; Danilo Harms (2019). "The oldest short-tailed whipscorpion (Schizomida): a new genus and species from the Upper Cretaceous amber of northern Myanmar". Cretaceous Research. in press: Article 104227. doi:10.1016/j.cretres.2019.104227.
  4. Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 615–617. ISBN   0-03-056747-5.
  5. Coddington J.A. et al. "Arachnida", p. 306, in: J. Cracraft (ed.) Assembling the Tree of Life, pp. 296-318
  6. Humphreys, W.F., et al. (1989) The biology of Schizomus vinei (Chelicerata: Schizomida) in the caves of Cape Range, Western Australia. J. ZOol. Lond. 217: 177-201.
  7. Geological history and phylogeny of Chelicerata

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