
Spider taxonomy is the part of
taxonomy
image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy
Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...
that is concerned with the science of naming, defining and classifying all
spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s, members of the Araneae
order of the
arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
class
Class, Classes, or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used d ...
Arachnida, which has more than 52,700 described
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
. However, there are likely many species that have escaped the human eye as well as
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.
Arachnologists
Arachnology is the science, scientific study of arachnids, which comprise spiders and related invertebrates such as scorpions, Pseudoscorpionida, pseudoscorpions, Opiliones, harvestmen, Tick, ticks, and mites. Those who study spiders and other a ...
divide
spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s into two
suborders with about 136
families .
Due to constant research, with new species being discovered every month and others being recognized as
synonyms
A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...
, the number of species in the families is bound to change and only reflects the present state of knowledge. Nevertheless, the species numbers given here are useful as a guideline – see the
table of families at the end of the article.
History
Spider taxonomy can be traced to the work of Swedish naturalist
Carl Alexander Clerck
Carl Alexander Clerck (1709 – 22 July 1765) was a Sweden, Swedish entomologist and arachnology, arachnologist.
Clerck came from a family in the petty Swedish nobility, nobility and entered the University of Uppsala in 1726. Little is known of hi ...
, who in 1757 published the first
binomial scientific names of some 67 spiders species in his ''
Svenska Spindlar'' ("Swedish Spiders"), one year before
Linnaeus
Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
named over 30 spiders in his
''Systema Naturae''. In the ensuing 250 years, thousands more species have been described by researchers around the world, yet only a dozen taxonomists are responsible for more than one-third of all species described. The most prolific authors include
Eugène Simon
Eugène Louis Simon (; 30 April 1848 – 17 November 1924) was a French naturalist who worked particularly on insects and spiders, but also on birds and plants. He is by far the most prolific spider Taxonomy (biology), taxonomist in history, ...
of France,
Norman Platnick and
Herbert Walter Levi of the United States,
Embrik Strand
Embrik Strand (2 June 1876 – 3 November 1947) was an entomologist and arachnologist who classified many insect and spider species, including the greenbottle blue tarantula.
Life and career
Strand was born in Ål, Norway. He studied at t ...
of Norway, and
Tamerlan Thorell
Tord Tamerlan Teodor Thorell (3 May 1830 – 22 December 1901) was a Sweden, Swedish arachnologist.
Thorell studied spiders with Giacomo Doria at the Museo Civico di Storia Naturale de Genoa. He corresponded with other arachnologists, such as Oc ...
of Sweden, each having described well over 1,000 species.
Overview of phylogeny
At the very top level, there is broad agreement on the
phylogeny
A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...
and hence classification of spiders, which is summarized in the
cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
below. The three main
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s into which spiders are divided are shown in bold; , they are usually treated as one suborder,
Mesothelae, and two infraorders,
Mygalomorphae and
Araneomorphae
The Araneomorphae (also called the Labidognatha or "true spiders") are an infraorder of spiders. They are distinguishable by chelicerae (fangs) that point diagonally forward and cross in a pinching action, in contrast to the Mygalomorphae (taran ...
, grouped into the suborder
Opisthothelae. The Mesothelae, with about 194 species in 8 genera , make up a very small proportion of the total of around 52,750 known species. Mygalomorphae species comprise around 7% of the total, the remaining 93% being in the Araneomorphae.
[Species counts from , family classification from .]
The Araneomorphae are divided into two main groups: the
Haplogynae and the
Entelegynae. The Haplogynae make up about 10% of the total number of spider species, the Entelegynae about 83%.
[ The phylogenetic relationships of the Haplogynae, Entelegynae and the two smaller groups Hypochiloidea and Austrochiloidea remain uncertain . Some analyses place both Hypochiloidea and Austrochiloidea outside Haplogynae; others place the Austrochiloidea between the Haplogynae and the Entelegynae; the Hypochiloidea have also been grouped with the Haplogynae. Earlier analyses regarded the Hypochiloidea as the sole representatives of a group called the Paleocribellatae, with all other araneomorphs placed in the Neocribellatae.
The Haplogynae are a group of araneomorph spiders with simpler male and female reproductive anatomy than the Entelegynae. Like the mesotheles and mygalomorphs, females have only a single genital opening ( gonopore), used both for copulation and egg-laying; males have less complex palpal bulbs than those of the Entelegynae. Although some studies based on both morphology and DNA suggest that the Haplogynae form a ]monophyletic
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:
# the grouping contains its own most recent co ...
group (i.e. they comprise all the descendants of a common ancestor), this hypothesis has been described as "weakly supported", with most of the distinguishing features of the group being inherited from ancestors shared with other groups of spiders, rather than being clearly indicative of a separate common origin (i.e. being synapomorphies). One phylogenetic hypothesis based on molecular data shows the Haplogynae as a paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
group leading to the Austrochilidae and Entelegynae.
The Entelegynae have a more complex reproductive anatomy: females have two "copulatory pores" in addition to the single genital pore of other groups of spiders; males have complex palpal bulbs, matching the female genital structures ( epigynes). The monophyly of the group is well supported in both morphological and molecular studies. The internal phylogeny of the Entelegynae has been the subject of much research. Two groups within this clade contain the only spiders that make vertical orb webs: the Deinopoidea are cribellate – the adhesive properties of their webs are created by packets of thousands of extremely fine loops of dry silk; the Araneoidea are ecribellate – the adhesive properties of their webs are created by fine droplets of "glue". In spite of these differences, the webs of the two groups are similar in their overall geometry. The evolutionary history of the Entelegynae is thus intimately connected with the evolutionary history of orb webs. One hypothesis is that there is a single clade, Orbiculariae, uniting the orb web makers, in whose ancestors orb webs evolved. A review in 2014 concluded that there is strong evidence that orb webs evolved only once, although only weak support for the monophyly of the Orbiculariae. One possible phylogeny is shown below; the type of web made is shown for each terminal node in order of the frequency of occurrence.
If this is correct, the earliest members of the Entelegynae made webs defined by the substrate on which they were placed (e.g. the ground) rather than suspended orb webs. True orb webs evolved once, in the ancestors of the Orbiculariae, but were then modified or lost in some descendants.
An alternative hypothesis, supported by some molecular phylogenetic studies, is that the Orbiculariae are paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
, with the phylogeny of the Entelegynae being as shown below.
On this view, orb webs evolved earlier, being present in the early members of the Entelegynae, and were then lost in more groups, making web evolution more convoluted, with different kinds of web having evolved separately more than once. Future advances in technology, including comparative genomics studies, and whole-genome sampling should lead to "a clearer image of the evolutionary chronicle and the underlying diversity patterns that have resulted in one of the most extraordinary radiations of animals".
Suborder Mesothelae
Mesothelae resemble the Solifugae
Solifugae is an Order (biology), order of Arachnid, arachnids known variously as solifuges, sun spiders, camel spiders, and wind scorpions. The order includes more than 1,000 described species in about 147 genus, genera. Despite the common names, ...
("wind scorpions" or "sun scorpions") in having segmented plates on their abdomens that create the appearance of the segmented abdomens of these other arachnids. They are both few in number and also limited in geographical range.
*† Arthrolycosidae (primitive spiders, extinct)
*† Arthromygalidae (primitive spiders, extinct)
* Liphistiidae (primitive burrowing spiders)
* Heptathelidae (primitive burrowing spiders)
Suborder Opisthothelae
Suborder Opisthothelae contains the spiders that have no plates on their abdomens. Opisthothelae is divided into two infraorders, Mygalomorphae and Araneomorphae, which can be distinguished by the orientation of their fangs. It can be somewhat difficult on casual inspection to determine whether the fang orientation would classify a spider as a mygalomorph or araneomorph. The spiders that are called " tarantulas" in English are so large and hairy that inspection of their fangs is hardly necessary to categorize one of them as a mygalomorph. Other, smaller, members of this suborder, however, look little different from the araneomorphs. (See the picture of '' Sphodros rufipes'' below.) Many araneomorphs are immediately identifiable as such since they are found on webs designed for the capture of prey or exhibit other habitat choices that eliminate the possibility that they could be mygalomorphs.
Infraorder Mygalomorphae
Spiders in infraorder Mygalomorphae are characterized by the vertical orientation of their fangs and the possession of four book lungs.
Infraorder Araneomorphae
Most, if not all, of the spiders one is likely to encounter in everyday life belong to infraorder Araneomorphae
The Araneomorphae (also called the Labidognatha or "true spiders") are an infraorder of spiders. They are distinguishable by chelicerae (fangs) that point diagonally forward and cross in a pinching action, in contrast to the Mygalomorphae (taran ...
. It includes a wide range of spider families, including the orb-weaver spiders that weave their distinctive webs in gardens, the cobweb spiders that frequent window frames and the corners of rooms, the crab spiders that lurk on flowers waiting for nectar- and pollen-gathering insects, the jumping spiders that patrol the outside walls of buildings, and so on. They are characterized by having fangs whose tips approach each other as they bite, and (usually) having one pair of book lungs.
Classification above families
Spiders were long classified into families that were then grouped into superfamilies, some of which were in turn placed into a number of higher taxa below the level of infraorder. When more rigorous approaches, such as cladistics
Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...
, were applied to spider classification, it became clear that most of the major groupings used in the 20th century were not supported. Many were based on shared characteristics inherited from the ancestors of multiple clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s ( plesiomorphies), rather than being distinct characteristics originating in the ancestors of that clade only ( apomorphies). According to Jonathan A. Coddington in 2005, "books and overviews published prior to the last two decades have been superseded". Listings of spiders, such as the World Spider Catalog, currently ignore classification above the family level.
At the higher level, the phylogeny of spiders is now often discussed using informal clade names, such as the " RTA clade", the "Oval Calmistrum" clade or the "Divided Cribellum" clade. Older names previously used formally are used as clade names, e.g. Entelegynae and Orbiculariae.
Table of families
Notes
References
Bibliography
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External links
Abbreviations for Insect and Spider Collections of the World
International Commission on Zoological Nomenclature
European and Australian spiders - info and identification
Spiders of Europe and Greenland
Information about the largest spider
{{Taxonomy of...
Taxonomy
image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy
Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...