Mygalomorphae

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Mygalomorphae
Temporal range: Triassic to present
Mouse spider.jpg
Missulena bradleyi, a mouse spider
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Suborder: Opisthothelae
Infraorder: Mygalomorphae
Pocock, 1892 [1]
Families

See text

Diversity
About 20 families

The Mygalomorphae, or mygalomorphs, are an infraorder of spiders. The name is derived from the Greek mygalē, meaning "shrew", plus morphē meaning form or shape. [2] An older name for the group is Orthognatha, derived from the orientation of the fangs which point straight down and do not cross each other (as they do in the araneomorphs). In 1802, Charles Athanase Walckenaer separated mygalomorph spiders into a separate genus, Mygale, leaving all other spiders in Aranea.

Contents

Description

This group of spiders comprises mostly heavy-bodied, stout-legged spiders including tarantulas, Australian funnel-web spiders, mouse spiders, and various families of spiders commonly called trapdoor spiders.

Like the "primitive" suborder of spiders Mesothelae, they have two pairs of book lungs, and downward-pointing chelicerae. Because of this, the two groups were once believed to be closely related. Later it was realized that the common ancestors of all spiders had these features (a state known as symplesiomorphy). Following the branching into the suborders of Mesothelae and Opisthothelae, the mygalomorphs retained them, while their fellow Opisthothelae members, the araneomorphs, evolved new "modern" features, including a cribellum and cross-acting fangs. [3] Mesotheles retain the external abdominal segmentation of ancestral arachnids and have at least vestiges of four pairs of spinnerets, whereas mygalomorphs lack abdominal segmentation (like other opistotheles) and have a reduced number of spinnerets, often only two pairs. [4]

Like spiders in general, most species of Mygalomorphae have eight eyes, one pair of principal and three pairs of secondary eyes.

Chelicerae of a black wishbone spider (Nemesiidae) Black Wishbone.jpg
Chelicerae of a black wishbone spider (Nemesiidae)

Their chelicerae and fangs are large and powerful and have ample venom glands that lie entirely within their chelicerae. These weapons, combined with their size and strength, make Mygalomorph spiders powerful predators. Many of these spiders are well adapted to killing other large arthropods and will also sometimes kill small mammals, birds, and reptiles. Despite their fearsome appearance and reputation, most mygalomorph spiders are not harmful to humans, with the exception of the Australian funnel-web spiders, especially those of the genus Atrax .[ citation needed ]

While the world's biggest spiders are mygalomorphs— Theraphosa blondi has a body length of 10 cm (3.9 in) and a leg span of 28 cm (11 in)—some species are less than one millimeter (0.039 in) long. Mygalomorphs are capable of spinning at least slightly adhesive silk, and some build elaborate capture webs that approach a meter in diameter. [3]

Unlike Araneomorphae, which die after about a year, Mygalomorphae can live for up to 25 years, and some do not reach maturity until they are about six years old. [5] Some flies in the family Acroceridae that are endoparasites of mygalomorphs may remain dormant in their book lungs for as long as 20 years before beginning their development and consuming the spider.[ citation needed ]

One female trapdoor spider, first recorded in a survey in 1974 in Western Australia, is known to have lived for 43 years. [6]

Taxonomy

Evolution

Sphodros rufipes, an atypical mygyalomorph Sphodros rufines.JPG
Sphodros rufipes , an atypical mygyalomorph

Megarachne servinei was thought to be a giant mygalomorph from the Upper Carboniferous (about 350 million years ago), but was later found to be a eurypterid. [7] The oldest known mygalomorph is Rosamygale grauvogeli (Hexathelidae) from the Triassic of northeastern France. No mygalomorphs from the Jurassic have yet been found. [8]

The number of families and their relationships have both been undergoing substantial changes since a cladogram showing family relationships was published in 2005, [9] with two significant studies in 2018. [10] [11] The division of Mygalomorphae into two superfamilies, Atypoidea and Avicularioidea, has been established in many studies. The Atypoidea retain some vestiges of abdominal segmentation in the form of dorsal tergites; the Avicularioidea lack these. Molecular phylogenetic studies undertaken between 2012 and 2017 have found somewhat different relationships within the Avicularioidea. Some families appear not to be monophyletic and further changes are possible in the future. [4]

Mygalomorphae tend to be very morphologically conserved, which makes it difficult to find reliable morphological features to use in taxonomy. It has been hypothesized that because Mygalomorphae tend to be fossorial and live in tubular webs, they are subjected to similar selective pressures, so most species should evolve in similar ways. Additionally, this may also mean that homoplasies are more likely to occur, further complicating taxonomy based on morphology. [12]

Phylogeny

The relationships of taxa in the Mygalomorphae were restructured based on a comprehensive phylogenetic study by Opatova et al. (2020) [13] The generic composition of the families Ctenizidae, Cyrtaucheniidae, Dipluridae, and Nemesiidae were relimited. Five subfamilies were raised to the rank of family: Anamidae, Euagridae, Ischnothelidae, Pycnothelidae, and Bemmeridae. Three new families were created: Entypesidae, Microhexuridae, and Stasimopidae. Lastly, a new subfamily, Australothelinae, was generated and placed in the family Euagridae.

The preferred cladogram from Optova et al. (2020) is: [13]

Mygalomorphae
Atypoidea

Hexurellidae

Mecicobothriidae

Atypidae

Megahexuridae

Antrodiaetidae

Avicularioidea

Ischnothelidae

Microhexuridae

Hexathelidae

Euagridae

Porrhothelidae

Macrothelidae

Bipectina

Paratropididae

Stasimopidae

Venom Clade

Atracidae

Actinopodidae

Domiothelina

Halonoproctidae

Migidae

Idiopidae

Ctenizidae

Euctenizidae

Crassitarsae
Theraphosoidina

Bemmeridae

Barychelidae

Theraphosidae

"Nemesioidina"

Nemesiidae

Pycnothelidae

Dipluridae

Cyrtaucheniidae

Anamidae

Entypesidae

Microstigmatidae

Families

Key
Genera1≥2≥10≥100
Species1–9≥10≥100≥1000
Mygalomorphae families [note 1]
FamilyGeneraSpeciesCommon nameExample
Atypoidea: [4]
Antrodiaetidae 437folding trapdoor spiders Atypoides riversi
Atypidae 354atypical tarantulas or purseweb spiders Sphodros rufipes (red legged purseweb spider)
Hexurellidae 14 Hexurella pinea
Mecicobothriidae 12dwarf tarantulas or sheet funnel-web spiders Mecicobothrium thorelli
Megahexuridae 11 Megahexura fulva
Avicularioidea: [4]
Actinopodidae 373 Missulena bradleyi (Eastern mouse spider)
Anamidae 985 Aname atra
Atracidae 335Australian funnel-web spidersAtrax robustus (Sydney funnel-web spider)
Barychelidae 42294Brushed trapdoor spiders Sason sundaicum
Bemmeridae 235 Spiroctenus personatus
Ctenizidae 25cork-lid trapdoor spiders Cteniza sauvagesi
Cyrtaucheniidae 8107wafer trapdoor spiders Fufius lucasae
Dipluridae 893Curtain-web spiders Diplura lineata
Entypesidae 337 Entypesa andohahela
Euagridae 1281 Euagrus formosanus
Euctenizidae 776 Aptostichus simus
Halonoproctidae 693 Bothriocyrtum californicum (California trapdoor spider)
Hexathelidae 745(Australian) funnel-web spiders Hexathele hochstetteri
Idiopidae 22407armored trapdoor spiders Idiosoma nigrum (black rugose trapdoor spider)
Ischnothelidae 526 Ischnothele caudata
Macrothelidae 135 Macrothele calpeiana (Spanish funnel-web spider)
Microhexuridae 12Microhexura montivaga (Spruce-fir moss spider)
Microstigmatidae 1241 Envia garciai
Migidae 11102tree trapdoor spiders Calathotarsus simoni
Nemesiidae 24195 Amblyocarenum nuragicus
Paratropididae 517baldlegged spiders Paratropis tuxtlensis
Porrhothelidae 15 Porrhothele antipodiana (black tunnelweb spider)
Pycnothelidae 681 Stanwellia hoggi
Stasimopidae 147 Stasimopus mandelai
Theraphosidae 147991tarantulasTheraphosa blondi (Goliath birdeater)

Historical classification

In 1985, Robert Raven published a monograph of the Mygalomorphae in which he proposed an internal classification for the Mygalomorphae, based on morphological features. In 2020, Opatova et. al. commented "In short, much of today’s classification scheme dates back to Raven (1985)". [13] Raven used various compound ranks, such as "gigapicoorder" and "hyperpicoorder". Ignoring these unusual rank names, his classification can be shown diagrammatically: [15]

Tuberculotae
Mecicobothrioidina

Mecicobothriidae

Microstigmatidae

Orthopalpae
Hexatheloidina

Hexathelidae

Quadrithelina
Dipluroida

Dipluridae

Crassitarsae
Nemesioida

Nemesiidae

Theraphosoidina
Superfamily Theraphosoidea

Theraphosidae

Paratropididae

Superfamily Barycheloidea

Barychelidae

Fornicephalae
Atypoidina

Atypidae

Antrodiaetidae

Rastelloidina
Cyrtaucheniina

Cyrtaucheniidae

Domiothelina
Idiopina

Idiopidae

Ctenizoidina
Superfamily Ctenizoidea

Ctenizidae

Superfamily Migoidea

Migidae

Actinopodidae

Subsequent research, largely based on molecular phylogenetic studies, has not upheld some of Raven's groupings. In particular his primary division between Tuberculotae and Fornicephalae has been replaced by a very different division between Atypoidea (expanded from Raven's Atypoidina) and Avicularioidea, which has no counterpart in his system. As another example, the families Mecicobothriidae and Microstigmatidae, which Raven placed in Mecicobothrioidina (a "gigapicoorder"), are now placed very far apart in the Atypoidea and Avicularioidea respectively. Other groups, such as Crassitarsae and Domiothelina, are more recognizable, allowing for some changes in family circumscriptions. [13]

Distribution

Most members of this infraorder occur in the tropics and subtropics, but their range can extend farther north, e.g. into the southern and western regions of the United States. Only a few occur in Europe: 12 species from the families Atypidae, Nemesiidae, Ctenizidae, Macrothelidae, Theraphosidae, and Cyrtaucheniidae.

Despite their limited range, currently, it is suggested that the Mygalomorphae were distributed worldwide before the breakup of Pangaea. [8]

Related Research Articles

Dipluridae Family of spiders

The family Dipluridae, known as curtain-web spiders are a group of spiders in the infraorder Mygalomorphae, that have two pairs of booklungs, and chelicerae (fangs) that move up and down in a stabbing motion. A number of genera, including that of the Sydney funnel-web spider (Atrax), used to be classified in this family but have now been moved to Hexathelidae.

Liphistiidae Family of spiders

The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the suborder Mesothelae. In Japan, the Kimura spider is well known.

Ctenizidae

Ctenizidae is a small family of medium-sized mygalomorph spiders that construct burrows with a cork-like trapdoor made of soil, vegetation and silk. They may be called trapdoor spiders, as are similar species, such as those of the families Liphistiidae, Barychelidae, Cyrtaucheniidae and some species in Idiopidae and Nemesiidae. In 2018, the family Halonoproctidae was split off from Ctenizidae, leaving only three genera.

Spider taxonomy

Spider taxonomy is that part of taxonomy that is concerned with the science of naming, defining and classifying all spiders, members of the Araneae order of the arthropod class Arachnida with about 46,000 described species. However, there are likely many species that have escaped the human eye to this day, and many specimens stored in collections waiting to be described and classified. It is estimated that only one third to one half of the total number of existing species have been described.

<i>Stanwellia</i> Genus of spiders

Stanwellia is a genus of South Pacific araneomorph spiders in the family Pycnothelidae. It was first described by W. J. Rainbow & R. H. Pulleine in 1918. Originally placed with the curtain-web spiders, it was transferred to the funnel-web trapdoor spiders in 1985, then to the Pycnothelidae in 2020. It is a senior synonym of Aparua.

Euctenizidae Family of spiders

The Euctenizidae are a family of mygalomorph spiders. They are now considered to be more closely related to Idiopidae.

<i>Entychides</i> Genus of spiders

Entychides is a genus of mygalomorph trapdoor spiders in the family Euctenizidae, and was first described by Eugène Simon in 1888. Originally placed with the Ctenizidae, it was moved to the wafer trapdoor spiders in 1985, then to the Euctenizidae in 2012.

Homostola is a genus of African araneomorph spiders in the family Bemmeridae. It was first described by Eugène Louis Simon in 1892. Originally placed with the Ctenizidae, it was transferred to the wafer trapdoor spiders in 1985, and to the Bemmeridae in 2020. It is a senior synonym of Stictogaster and Paromostola.

Entypesa is a genus of African mygalomorph spiders in the family Entypesidae. It was first described by Eugène Louis Simon in 1902. Originally placed with the curtain-web spiders, it was transferred to the funnel-web trapdoor spiders in 1985, then to the Entypesidae in 2020. It is a senior synonym of Pseudohermacha.

Hermacha is a genus of araneomorph spiders in the family Entypesidae. It was first described by Eugène Louis Simon in 1889. Originally placed with the Ctenizidae, it was transferred to the funnel-web trapdoor spiders in 1985, then to the Entypesidae in 2020. It is a senior synonym of Damarchodes and Hermachola.

Pionothele is a genus of African mygalomorph spiders in the family Pycnothelidae. It was first described by William Frederick Purcell in 1902. As of June 2020 it contains three species, found in Namibia and South Africa: P. capensis, P. gobabeb, and P. straminea. Originally placed with the Ctenizidae, it was transferred to the funnel-web trapdoor spiders in 1985, then to the Pycnothelidae in 2020.

Spiroctenus is a genus of African araneomorph spiders in the family Bemmeridae. It was first described by Eugène Louis Simon in 1889. Originally placed with the Ctenizidae, it was transferred to the funnel-web trapdoor spiders in 1985, and to the Bemmeridae in 2020. It is a senior synonym of Bemmeris, Bessia, and Ctenonemus.

Avicularioidea

Avicularioidea is a clade of mygalomorph spiders, one of the two main clades into which mygalomorphs are divided. It has been treated at the rank of superfamily.

Pycnothelidae is a family of mygalomorph spiders first described in 1917. It was downgraded to a subfamily of the funnel-web trapdoor spiders in 1985, but returned to family status in 2020.

Euagridae is a family of mygalomorph spiders. The group was first described as a tribe in 1979 by Robert Raven, who in 1985 elevated it to a subfamily. In 2020, Optova et al. elevated it further to a family.

Bipectina

Bipectina is a clade of avicularioid mygalomorph spiders first proposed by Pablo A. Goloboff in 1993, based on a morphological cladistic analysis. The clade was marked by a number of morphological features, and in particular by the presence of two rows of teeth on the superior tarsal claws of the legs of both sexes, meaning that the claws were bipectinate. The clade was supported by some subsequent analyses, although not all. A major phylogenetic study in 2020 upheld the monophyly of the clade, which contained 19 of the 25 accepted families of the Avicularioidea.

Domiothelina

Domiothelina is a clade of avicularioid mygalomorph spiders first proposed by Robert J. Raven in 1985, based on a morphological cladistic analysis. Raven characterized the clade by a number of shared features, including the domed apical segment of the posterior lateral spinnerets. The clade has been supported to some degree by subsequent molecular analyses, although with a somewhat different composition.

Crassitarsae

Crassitarsae is a clade of avicularioid mygalomorph spiders first proposed by Robert J. Raven in 1985, based on a morphological cladistic analysis. Raven characterized the clade by a number of shared features, including the presence of some scopulae on the tarsi. The clade has been supported to some degree by subsequent molecular analyses, although with a somewhat different composition.

Theraphosoidina

Theraphosoidina is a clade of avicularioid mygalomorph spiders first proposed by Robert J. Raven in 1985, based on a morphological cladistic analysis. Raven included three families: Theraphosidae, Paratropididae and Barychelidae. Subsequent molecular phylogenetic studies upheld the relationship between the Theraphosidae and Barychelidae, but found that Paratropidae fell outside the clade.

Nemesioidina

Nemesioidina is a clade of avicularioid mygalomorph spiders proposed in 2020, based on a molecular phylogenetic analysis.

References

  1. Dunlop, Jason A. & Penney, David (2011). "Order Araneae Clerck, 1757" (PDF). In Zhang, Z.-Q. (ed.). Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness. Zootaxa. Auckland, New Zealand: Magnolia Press. ISBN   978-1-86977-850-7 . Retrieved 2015-10-31.
  2. "mygalomorph". Oxford Dictionaries. Archived from the original on 2016-05-21. Retrieved 2016-02-02.
  3. 1 2 Coddington, Jonathan A. & Levi, Herbert W. (1991). "Systematics and evolution of spiders (Araneae)". Annual Review of Ecology and Systematics. 22: 565–592. doi:10.1146/annurev.es.22.110191.003025. JSTOR   2097274. S2CID   55647804.
  4. 1 2 3 4 Wheeler, Ward C.; Coddington, Jonathan A.; Crowley, Louise M.; Dimitrov, Dimitar; Goloboff, Pablo A.; Griswold, Charles E.; et al. (2016). "The spider tree of life: Phylogeny of Araneae based on target-gene analyses from an extensive taxon sampling". Cladistics. 33 (6): 574–616. doi:10.1111/cla.12182. S2CID   35535038.
  5. "About Spiders". CSIRO. Archived from the original on 2015-09-24. Retrieved 2017-02-18.
  6. World's oldest spider dies aged 43 in Western Australia Archived 2018-04-29 at the Wayback Machine ABC News, 28 April 2018. Retrieved 2018-04-29.
  7. Selden, P.A.; Corronca, J.A. & Hünicken, M.A. (2005). "The true identity of the supposed giant fossil spider Megarachne". Biology Letters. 1 (1): 44–48. doi:10.1098/rsbl.2004.0272. PMC   1629066 . PMID   17148124.
  8. 1 2 Selden, P.A.; da Costa Casado, F. & Vianna Mesquita, M. (2005). "Mygalomorph spiders (Araneae: Dipluridae) from the Lower Cretaceous Crato Lagerstätte, Araripe Basin, north-east Brazil". Palaeontology. 49 (4): 817–826. doi:10.1111/j.1475-4983.2006.00561.x. hdl: 1808/8355 .
  9. Coddington, Jonathan A. (2005). "Phylogeny and classification of spiders" (PDF). In Ubick, D.; Paquin, P.; Cushing, P.E. & Roth, V. (eds.). Spiders of North America: an identification manual. American Arachnological Society. pp. 18–24. Retrieved 2015-09-24.
  10. Hedin, Marshal; Derkarabetian, Shahan; Ramírez, Martín J.; Vink, Cor & Bond, Jason E. (2018). "Phylogenomic reclassification of the world's most venomous spiders (Mygalomorphae, Atracinae), with implications for venom evolution". Scientific Reports. 8 (1): 1636. doi:10.1038/s41598-018-19946-2. PMC   5785998 . PMID   29374214.
  11. Godwin, Rebecca L.; Opatova, Vera; Garrison, Nicole L.; Hamilton, Chris A. & Bond, Jason E. (2018). "Phylogeny of a cosmopolitan family of morphologically conserved trapdoor spiders (Mygalomorphae, Ctenizidae) using Anchored Hybrid Enrichment, with a description of the family, Halonoproctidae (Pocock, 1901)". Molecular Phylogenetics and Evolution. 126: 303–313. doi:10.1016/j.ympev.2018.04.008. ISSN   1055-7903. PMID   29656103.
  12. Bond, Jason E.; Hedin, Marshal (1 October 2006). "A total evidence assessment of the phylogeny of North American euctenizine trapdoor spiders (Araneae, Mygalomorphae, Cyrtaucheniidae) using Bayesian inference". Molecular Phylogenetics and Evolution. 41 (1): 70–85. doi:10.1016/j.ympev.2006.04.026. ISSN   1055-7903. PMID   16857391.
  13. 1 2 3 4 Opatova, Vera; Hamilton, Chris A.; Hedin, Marshal; Montes De Oca, Lauren; Král, Jiři; Bond, Jason E. (16 October 2019). "Phylogenetic Systematics and Evolution of the Spider Infraorder Mygalomorphae Using Genomic Scale Data". Systematic Biology. 69 (4): 671–707. doi:10.1093/sysbio/syz064. PMID   31841157.
  14. World Spider Catalog (2018), Currently valid spider genera and species.
  15. Raven, Robert J. (1985). "The spider infraorder Mygalomorphae (Araneae) : cladistics and systematics". Bulletin of the American Museum of Natural History. 182 (1): 1–180.

Notes

  1. Unless otherwise shown, currently accepted families and counts based on the World Spider Catalog version 19.0 as of 11 July 2018. [14] In the World Spider Catalog, "species" counts include subspecies. Assignment to sub- and infraorders based on Coddington (2005, p. 20) (when given there).

Bibliography