The cosmotropical spider family Theridiosomatidae is revised at the generic level to contain 9 genera: Theridiosoma O. Pickard-Cambridge, 1879, Ogulnius O. Pickard-Cambridge, 1882, Wendilgarda Keyserling, 1886, Epeirotypus O. Pickard-Cambridge, 1894, Baalzebub, new genus (type-species B. baubo, new species), Epilineutes, new genus (type-species Theridiosoma globosum O. Pickard-Cambridge), Plato, new genus (type-species P. troglodita, new species), Naatlo, new genus (type-species N. sutila, new species), and Chthonos, new name. Of the 22 genera historically associated with the family, 17 have been rejected, transferred, or synonymized. Theridilella Chamberlin and Ivie, 1936 (damaged specimen), and Allototua Bryant, 1945 (unique specimen lost), are considered unrecognizable nomina dubia; Haliger Mello-Leitão lacks the defining features of theridiosomatids and is considered incertae sedis. Diotherisoma di Caporiacco, 1947, is transferred to the Araneidae and Totua Keyserling, 1891, to the Linyphiidae. The previous transfers of Colphepeira Archer, 1941, to the Araneidae, Billima Simon, 1908, Helvidia Thorell, 1890, and Spheropistha Yaginuma, 1957, to the Theridiidae, Cyatholipulus Petrunkevitch, 1930, to the Symphytognathidae, Cyatholipus Simon, 1894, and Tekella Urquhart, 1894, to the Cyatholipinae (Tetragnathidae), and Parogulnius Archer, 1953, and Phricotelus Simon, 1895, to the Mysmenidae are not contested. The genus Andasta Simon, 1895, is synonymized with Theridiosoma, and Enthorodera Simon, 1907, and Cyathidea Simon, 1907, with Wendilgarda. Theridiosoma argentatum Keyserling, 1886, and T. radiosum (McCook, 1881) are synonymized with T. gemmosum (L. Koch, 1878), and Wendilgarda panamica Archer, 1953, W. hassleri Archer, 1953, and W. theridionina Simon, 1895, with W. clara Keyserling, 1886. Tecmessa tetrabuna Archer, 1958, and Epeirotypus gloriae Petrunkevitch, 1930, are transferred to Ogulnius. Maymena bruneti Gertsch, 1960, and Wendilgarda guacharo Brignoli, 1972, W. miranda Brignoli, 1972, and W. bicolor Keyserling, 1886, are transferred to Plato. Theridiosoma fauna Simon, 1897, T. splendidum (Taczanowski, 1873), and T. sylvicola Hingston, 1932, are transferred to Naatlo. Theridiosoma albinotatum Petrunkevitch, 1930, and T. brauni Wunderlich, 1976, are transferred to Baalzebub. Theridiosoma nigrum (Keyserling, 1886) is returned to Wendilgarda. The genus Tecmessa O. Pickard-Cambridge, 1882, is valid but the name is preoccupied (Tecmessa Burmeister, 1878: Lepidoptera); the new name Chthonos replaces it. The new genera Baalzebub, Epilineutes, Naatlo, and Plato, and the new species Baalzebub baubo, Plato troglodita, Naatlo sutila, and Epeirotypus chavarria are described. The sister taxon of the Theridiosomatidae is the Mysmenidae-Symphytognathidae-Anapidae clade. A cladogram for theridiosomatid genera is presented.
