The Mesothelae are a suborder of spiders that includes a single extant family, Liphistiidae, and a number of extinct families. This suborder is thought to form the sister group to all other living spiders, and to retain ancestral characters, such as a segmented abdomen with spinnerets in the middle and two pairs of book lungs. Members of Liphistiidae are medium to large spiders with eight eyes grouped on a tubercle. They are found only in China, Japan, and southeast Asia. The oldest known Mesothelae spiders are known from the Carboniferous, over 300 million years ago.
Leptonetidae is a family of small spiders adapted to live in dark and moist places such as caves. The family is relatively primitive having diverged around the Middle Jurassic period. They were first described by Eugène Simon in 1890.
Pimoidae is a small family of araneomorph spiders first described by J. Wunderlich in 1986. As re-circumscribed in 2021, it is monophyletic, and contained 85 species in two genera. It is closely related to the Linyphiidae, and is sometimes treated as synonymous with that family.
Pimoa is a genus of spiders in the family Pimoidae. Its sister genus is Nanoa.
Austrochilidae is a small spider family with nine species in two genera. Austrochilus and Thaida are endemic to the Andean forest of central and southern Chile and adjacent Argentina.
The Dionycha are a clade of spiders (Araneomorphae:Entelegynae), characterized by the possession of two tarsal claws with tufts of hairs (setae) beside them, which produce strong adhesion, enabling some species to climb glass. The circumscription of the group has varied widely; a 2021 analysis resulted in about 20 families, including Salticidae, Gnaphosidae, and Clubionidae.
The Agelenoidea or agelenoids are a superfamily or informal group of entelegyne araneomorph spiders. Phylogenetic studies since 2000 have not consistently recovered such a group, with more recent studies rejecting it.
Opisthothelae is a suborder of spiders within the order Araneae, containing Mygalomorphae and Araneomorphae, but excluding Mesothelae. The Opisthothelae are sometimes presented as an unranked clade and sometimes as a suborder of Araneae. In the latter case, Mygalomorphae and Araneomorphae are treated as infraorders.
Phrurolithidae is a family of araneomorph spiders, known as guardstone spiders. The family was first described by Nathan Banks in 1892. First included in the Corinnidae as the subfamily Phrurolithinae, later phylogenetic studies justified a separate family.
Hypochilus thorelli is a species of spider in the family Hypochilidae. Unlike almost all other araneomorph or "true" spiders, members of the family have four book lungs. They are often called "lampshade spiders" because of the shape of their webs which are usually built underneath ledges or projections. H. thorelli is found in the southern Appalachian Mountains of the eastern United States.
Hypochilus is a genus of North American lampshade spiders that was first described by George Marx in 1888.
Ectatosticta is a genus of East Asian lampshade spiders that was first described by Eugène Louis Simon in 1892.
Scopoides is a genus of ground spiders that was first described by Norman I. Platnick in 1989.
Phrurotimpus is a genus of araneomorph spiders first described by R. V. Chamberlin and Wilton Ivie in 1935. The name is a compound adjective meaning "guarding the stone". Originally added to the Liocranidae, it was moved to the Corinnidae in 2002, then to the Phrurolithidae in 2014. They have red egg sacs that look like flattened discs, often found on the underside of stones.
Phonotimpus is a genus of North American araneomorph spiders in the family Phrurolithidae. It was first described by Willis J. Gertsch and Louie Irby Davis in 1940, and placed with the Liocranidae. It was transferred to Corinnidae in 2002, then to the Phrurolithidae in 2014.
Xilithus is a genus of araneomorph spiders in the family Phrurolithidae. It was first described by Liu & Li in 2023 as a replacement name for Acrolithus.
