Lycosoidea is a
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 ...
or
superfamily of
araneomorph 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. The traditional
circumscription
Circumscription may refer to:
* Circumscribed circle
* Circumscription (logic)
*Circumscription (taxonomy)
* Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthr ...
was based on a feature of the eyes. The tapetum is a reflective layer at the back of the eye, thought to increase sensitivity in low light levels. Lycosoids were then defined by having a "grate-shaped" tapetum. Research from the late 1990s onwards suggests that this feature has evolved more than once, possibly as many as five times, so that the original Lycosoidea is
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 ...
.
[ Studies published in 2014 and 2015 suggest that a smaller group of families does form a clade.
The reflective attributes of the tapeta vary significantly among lycosoid spiders.]
Phylogeny
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 ...
of the Lycosoidea and related groups has been studied using both morphological and molecular data. Comparing these studies is complicated by the redrawing of family boundaries. Thus potential lycosoid genera placed in the family Miturgidae
Miturgidae is a family of araneomorph spiders that includes nearly 170 species in 29 genera worldwide. First described by Eugène Simon in 1886, it has been substantially revised, and includes the previous family Zoridae as a synonym, and exclude ...
in 1993, such as '' Uliodon'',[ have since been placed in the Zoropsidae. The family Ctenidae, placed in the Lycosoidea in many analyses, has been reduced by moving some genera into the new family Viridasiidae.
The "classical" ]circumscription
Circumscription may refer to:
* Circumscribed circle
* Circumscription (logic)
*Circumscription (taxonomy)
* Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthr ...
of the Lycosoidea was based on the possession of a grate-shaped tapetum in some or all of the indirect eyes. In 1993, Griswold concluded that the Lycosoidea so defined was monophyletic, although some of the lycosoid families (as then circumscribed) were not.[ (See the table below for the families included in this and later studies.) Stiphidiidae was later excluded from the Lycosoidea.][ Later studies have recovered a version of Lycosoidea as 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, although with varying compositions and placements within clades. Ramírez, as part of a study primarily directed at dionychans, suggested that a reduced Lycosoidea, consisting of only five families, was monophyletic. Ctenidae and Zoropsidae were excluded from the lycosoid clade. (Trechaleidae was not included in the study.) An alternative hypothesis explored by Ramírez also placed Thomisidae in the Lycosoidea. Polotow et al. (2015) concluded that a seven-family Lycosoidea was monophyletic. Of the "classical" lycosoid families, they put back Ctenidae left out by Ramírez (although saying that the family is not monophyletic), but additionally excluded Senoculidae. They supported Ramírez' alternative of placing Thomisidae in Lycosoidea.
Lycosoid families are located within the large RTA clade of araneomorph spiders.
References
Bibliography
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{{Taxonbar, from=Q54901
Araneomorphae
Arachnid superfamilies