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Uraraneida is an extinct order of
arachnid Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegar ...
s, known from fossils of
Middle Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...
,
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...
and possibly
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
age. Two genera of fossils have been definitively placed in this order: ''
Attercopus ''Attercopus'' is an extinct genus of arachnids, containing one species ''Attercopus fimbriunguis'', known from flattened cuticle fossils from the Panther Mountain Formation in Upstate New York. It is placed in the extinct order Uraraneida, sp ...
'' from the Devonian of
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
and '' Permarachne'' from the Permian of
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...
. In 2018, a third genus ''
Chimerarachne ''Chimerarachne'' is a genus of extinct arachnids, sometimes considered as spider itself,Dunlop, J. A., Penney, D. & Jekel, D. 2020A summary list of fossil spiders and their relatives In World Spider Catalog. Natural History Museum Bern, online ...
'', from the Cretaceous of
Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
was proposed to belong to this group, but this placement is disputed. When the first fossils were found, they were identified as
spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...
s, but now constitute the Uraraneida, a separate but closely related group.


Characteristics

The first fossil now placed in the order was found in
Gilboa, New York Gilboa is a town in Schoharie County, New York, United States. The population was 1,215 at the 2000 census. The Town of Gilboa is in the southern part of the county and is southwest of Albany. History The town was first settled around 1760 ...
. In 1987, it was initially tentatively placed in the extinct order
Trigonotarbida The order Trigonotarbida is a group of extinct arachnids whose fossil record extends from the late Silurian to the early Permian ( Pridoli to Sakmarian).Dunlop, J. A., Penney, D. & Jekel, D. 2020A summary list of fossil spiders and their relative ...
and named ''Gelasinotarbus''? ''fimbriunguis''. Later, partly on the basis of a supposed
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
, it was identified as a spider and named ''Attercopus fimbriunguis''. Further specimens of this species were found, and when examined in detail, along with those assigned to the genus ''Permarachne'', features inconsistent with their placement as spiders were revealed. Silk producing spigots are present, but are borne along the rear edges of ventral plates, not on appendage-like spinnerets, as in spiders. The specimens also have a long, jointed "tail" or flagellum at the end of the abdomen, after the
anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, ...
, a feature lacking in spiders but present in some other arachnids, such as uropygids.


Phylogeny and classification

A 2014 study placed the Uraraneida in the
Tetrapulmonata Tetrapulmonata is a non-ranked supra-ordinal clade of arachnids. It is composed of the extant orders Thelyphonida (whip scorpions), Schizomida (short-tailed whip scorpions), Amblypygi (tail-less whip scorpions) and Araneae (spiders). It is th ...
, a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
of arachnids defined by the
apomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...
(derived feature) of two pairs of book lungs. The Tetrapulmonata divide into two main clades, one of which, Serikodiastida (Greek for "silk workers"), unites Uraraneida and Araneae (spiders), groups that share the ability to produce and use silk. An alternative classification suggested by Wunderlich in 2015, based on the same phylogeny, makes Uraraneida a suborder of Araneae, with "true spiders" treated as suborder
Araneida Araneida is a subgroup of Tetrapulmonata. It was originally defined by Jörg Wunderlich in 2015 as a subgroup of Araneae, including all true spiders, with Wunderlich also including Uraraneida within Araneae., cited in Araneida was redefined by Wu ...
. In 2016, a fossil arachnid from the Pennsylvanian ("Late
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
") age was described under the name '' Idmonarachne brasieri''. It resembles uraraneids in lacking spinnerets, but unlike them resembles spiders in lacking a flagellum. The Late Carboniferous appears to be a time when there was a greater diversity of tetrapulmonate arachnids, of which the uraraneids were just one group. In 2018, two groups simultaneously published a new taxon, ''Chimerarachne'', which was considered either closely related to the Uraraneida, or a member of it.


Genera and species

Dunlop et al. (2015) accepted two species: * ''
Attercopus ''Attercopus'' is an extinct genus of arachnids, containing one species ''Attercopus fimbriunguis'', known from flattened cuticle fossils from the Panther Mountain Formation in Upstate New York. It is placed in the extinct order Uraraneida, sp ...
'' Selden & Shear, 1991 ** ''Attercopus fimbriunguis'' (Shear, Selden & Rolfe, 1987) – Devonian;
Gilboa, New York Gilboa is a town in Schoharie County, New York, United States. The population was 1,215 at the 2000 census. The Town of Gilboa is in the southern part of the county and is southwest of Albany. History The town was first settled around 1760 ...
* '' Permarachne'' Eskov & Selden, 2005 ** ''Permarachne novokshonovi'' Eskov & Selden, 2005 – Permian; Matveyevka,
Perm Krai Perm Krai (russian: Пе́рмский край, r=Permsky kray, p=ˈpʲɛrmskʲɪj ˈkraj, ''Permsky krai'', , ''Perem lador'') is a federal subject of Russia (a krai) that came into existence on December 1, 2005 as a result of the 2004 re ...
, Russia Huang et al. (2018) placed another species in this order: * ''
Chimerarachne ''Chimerarachne'' is a genus of extinct arachnids, sometimes considered as spider itself,Dunlop, J. A., Penney, D. & Jekel, D. 2020A summary list of fossil spiders and their relatives In World Spider Catalog. Natural History Museum Bern, online ...
'' ** ''Chimerarachne yingi'' – mid-
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
; Burmese amber


References

{{Taxonbar, from=Q3552134 Prehistoric arthropod orders Devonian arachnids Carboniferous arachnids Permian arachnids Devonian arthropods of North America Carboniferous arthropods of North America Permian arthropods of North America