N.B.: For a diagnosis and discussions of subfamilies, limits, and relationships, see Forster, Platnick & Coddington, 1990. With exception of Synotaxus, all other genera transferred from Synotaxidae to Physoglenidae by Dimitrov et al., 2017: 24.

Transferred to other families:
Calcarsynotaxus Wunderlich, 1995 -- see Physoglenidae
Chileotaxus Platnick, 1990 -- see Physoglenidae
Mangua Forster, 1990 -- see Physoglenidae
Meringa Forster, 1990 -- see Physoglenidae
Microsynotaxus Wunderlich, 2008 -- see Physoglenidae
Nomaua Forster, 1990 -- see Physoglenidae
Pahora Forster, 1990 -- see Physoglenidae
Pahoroides Forster, 1990 -- see Physoglenidae
Paratupua Platnick, 1990 -- see Physoglenidae
Physoglenes Simon, 1904 -- see Physoglenidae
Runga Forster, 1990 -- see Physoglenidae
Tupua Platnick, 1990 -- see Physoglenidae
Zeatupua Fitzgerald & Sirvid, 2009 -- see Physoglenidae

N.B.: transferred here from the Theridiidae by Forster, Platnick & Coddington, 1990: 96.

In synonymy:
Synotaxus anomalus (Chamberlin & Ivie, 1936) = Synotaxus turbinatus Simon, 1895 (Exline & Levi, 1965: 179).
Synotaxus pupularum Exline & Levi, 1965 = Synotaxus monoceros (Caporiacco, 1947) (Agnarsson, 2003: 726).
Synotaxus uncatus Simon, 1894 = Synotaxus longicaudatus (Keyserling, 1891) (Exline & Levi, 1965: 181).
Synotaxus wallsi Exline, 1950 = Synotaxus turbinatus Simon, 1895 (Exline & Levi, 1965: 179).

Synotaxus bonaldoi Santos & Rheims, 2005: 5, f. 2, 7-10 (Dmf).

Synotaxus brescoviti Santos & Rheims, 2005: 2, f. 1, 3-6 (Dmf).

Synotaxus ecuadorensis Exline, 1950a: 120, 3, 13 (Dm).
Synotaxus ecuadorensis Exline & Levi, 1965: 182, f. 22-27 (m, Df).

Synotaxus itabaiana Santos & Rheims, 2005: 9, f. 15-18 (Dmf).

Synotaxus jaraguari Souza, Brescovit & Araujo, 2017: 141, f. 1, 2A-F, 3A-D, 4A-D (Dmf).

Synotaxus leticia Exline & Levi, 1965: 183, f. 33-34 (Dm).

Argyrodes longicaudatus Keyserling, 1891: 209, pl. 8, f. 150 (Dmf).
Synotaxus uncatus Simon, 1894a: 495, f. 495-497 (nomen nudum).
Synotaxus uncatus Simon, 1895g: 131 (Dmf).
Synotaxus longicaudatus Exline & Levi, 1965: 181, f. 16-21 (mf, S).

Argyrodina monoceros Caporiacco, 1947a: 24 (Dm).
Conopistha monoceros Caporiacco, 1948a: 649, f. 57-59 (Tm from Argyrodina=Argyrodes).
Synotaxus pupularum Exline & Levi, 1965: 183, f. 28-29 (Df).
Synotaxus monoceros Exline & Levi, 1965: 184, f. 30-32 (Tm from Conopistha=Argyrodes).
Synotaxus monoceros Agnarsson, 2003: 726, f. 2A-F, 3A-I, 5F, 6B, D (m, Sf).
Synotaxus monoceros Agnarsson, 2004: 516, f. 1A-B, 89C (m).
Synotaxus monoceros Jocqué & Dippenaar-Schoeman, 2006: 242, f. 98f-g (m).
Synotaxus monoceros Agnarsson, Coddington & Knoflach, 2007: 384, f. 189-190, 197 (m).

Synotaxus siolii Santos & Rheims, 2005: 7, f. 11-14 (Dmf).

Synotaxus turbinatus Simon, 1894a: 495 (nomen nudum).
Synotaxus turbinatus Simon, 1895g: 131 (Dm).
Rhomphaea anomala Chamberlin & Ivie, 1936a: 41, pl. 10, f. 80 (Df).
Synotaxus anomalus Exline, 1950a: 111 (Tf from Rhomphaea=Argyrodes).
Synotaxus wallsi Exline, 1950a: 121, 2, 9-12 (Dmf).
Synotaxus turbinatus Exline & Levi, 1965: 179, f. 1-15 (mf, S).
Synotaxus turbinatus Forster, Platnick & Coddington, 1990: 96, f. 333-335, 378 (m).
Synotaxus turbinatus Coddington, 1990: 18, f. 89 (m).
Synotaxus turbinatus Griswold et al., 1998: 70, f. 19C (m).

Synotaxus waiwai Agnarsson, 2003: 731, f. 2G-M, 4A-I, 5A-E, G-H, 6A, C (Dmf).
Synotaxus waiwai Agnarsson, 2004: 516, f. 1C-D (m).
Synotaxus waiwai Agnarsson, Coddington & Knoflach, 2007: 384, f. 191 (m).