Spider taxonomy

The most prolific authors include Eugène Simon of France, Norman Platnick and Herbert Walter Levi of the United States, Embrik Strand of Norway, and Tamerlan Thorell of Sweden, each having described well over 1,000 species.

[note 1] The phylogenetic relationships of the Haplogynae, Entelegynae and the two smaller groups Hypochiloidea and Austrochiloidea remain uncertain as of 2015[update].

[10] Earlier analyses regarded the Hypochiloidea as the sole representatives of a group called the Paleocribellatae, with all other araneomorphs placed in the Neocribellatae.

Like the mesotheles and mygalomorphs, females have only a single genital opening (gonopore), used both for copulation and egg-laying;[12] males have less complex palpal bulbs than those of the Entelegynae.

[15] One phylogenetic hypothesis based on molecular data shows the Haplogynae as a paraphyletic group leading to the Austrochilidae and Entelegynae.

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.

An alternative hypothesis, supported by some molecular phylogenetic studies, is that the Orbiculariae are paraphyletic, with the phylogeny of the Entelegynae being as shown below.

[18] Future advances in technology, including comparative genomics studies,[2] 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".

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.

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, were applied to spider classification, it became clear that most of the major groupings used in the 20th century were not supported.