In synonymy:
Caseola Emerton, 1909 = Maso Simon, 1884 (Bishop & Crosby, 1935c: 234)

type Erigone sundevalli Westring, 1851; gender masculine

N.B.: considered a senior synonym of Caseola Emerton, 1909: 186 [urn:lsid:nmbe.ch:spidergen:06058] (type C. herbicola Emerton, 1909 = Maso sundevalli (Westring, 1851)) by Bishop & Crosby, 1935c: 234; not a senior synonym of Satilatlas Keyserling, 1886 (Millidge, 1981c: 243, rejected Strand, 1906a: 448 and Chamberlin & Ivie, 1947b: 46).

Transferred to other genera:
Maso alticeps (Emerton, 1909) -- see Metopobactrus
Maso marxi matanuskae Chamberlin, 1949 -- see Satilatlas
Maso nivalis Schenkel, 1919 -- see Scotinotylus
Maso perplexus Chamberlin & Ivie, 1939 -- see Diplocentria
Maso sarcocuon (Crosby & Bishop, 1927) -- see Blestia
Maso serratipes Simon, 1918 -- see Satilatlas
Maso spinipes Wiehle, 1967 -- see Pocadicnemis

In synonymy:
Maso columbiensis (Crosby, 1903, T from Acartauchenius) = Maso politus Banks, 1896 (Ivie, 1967: 129).
Maso frontatus (Banks, 1892) = Maso sundevalli (Westring, 1851) (Bishop & Crosby, 1935c: 234).
Maso herbicola (Emerton, 1909, T from Caseola) = Maso sundevalli (Westring, 1851) (Bishop & Crosby, 1935c: 234).
Maso westringi (Simon, 1882) = Maso sundevalli (Westring, 1851) (Chyzer & Kulczyński, 1894: 133).

Maso douro Bosmans & Cardoso, in Bosmans, Cardoso & Crespo, 2010: 28, f. 47-49 (Dm).

Maso sundevalli Simon, 1884a: 802, f. 798-799 (mf; misidentified per Simon, 1894a: 641).
Maso gallica Simon, 1894a: 640, f. 744-746 (Dm).
Maso gallica Lessert, 1910b: 208 (Df).
Maso gallica Simon, 1926: 328, 478, f. 544-547 (mf).
Maso gallica Locket & Millidge, 1953: 233, f. 133B, D-E (mf).
Maso gallica Wiehle, 1960a: 16, f. 1-8 (mf).
Maso gallica Millidge, 1977: 19, f. 64 (m).
Maso gallicus Millidge, 1984b: 250, f. 112 (f).
Maso gallicus Roberts, 1987: 54, f. 20b (mf).
Maso gallicus Tanasevitch, 1990: 108, f. 22.34, 24.45 (mf).
Maso gallicus Heimer & Nentwig, 1991: 208, f. 558 (mf).
Maso gallicus Bosmans, 2007: 131, f. 91-95 (mf).
Maso gallicus Seropian et al., 2023: 250, f. 41, S2 (mf).

Maso krakatauensis Bristowe, 1931c: 1398, f. 10-12 (Df).

Maso navajo Chamberlin, 1949: 535, f. 162 (Df).

Maso polita Banks, 1896e: 67 (Dmf).
Acartauchenius columbiensis Crosby, 1905a: 329, pl. 28, f. 11, pl. 29, f. 9 (Dm) [urn:lsid:nmbe.ch:spidersp:058563].
Maso polita Bishop & Crosby, 1935c: 232, pl. 19, f. 33-34 (m).
Maso polita Ivie, 1967: 128 (S of Acartauchenius columbiensis).

Erigone sundevallii Westring, 1851: 44 (Df).
Erigone sundevalli Westring, 1861: 291 (Dm).
Microneta sundevalli Menge, 1869: 232, pl. 45, f. 131 (Dmf).
Neriene sundevalli O. Pickard-Cambridge, 1871a: 450.
Erigone westringi Simon, 1882d: 256 (Dm) [urn:lsid:nmbe.ch:spidersp:058551].
Maso westringi Simon, 1884a: 864, f. 800 (m, Df).
Phylloeca sundevalli Dahl, 1886: 101.
Ceratinopsis frontatus Banks, 1892a: 33, pl. 5, f. 63 (Df) [urn:lsid:nmbe.ch:spidersp:058565].
Maso sundevalli Chyzer & Kulczyński, 1894: 133, pl. 5, f. 15 (mf, S of Maso westringi).
Maso sundevalli Simon, 1894a: 641, 670 (S of Maso westringi).
Maso sundevalli Becker, 1896: 174, pl. 12, f. 21 (mf).
Maso frontatus Banks, 1896e: 67 (T from Ceratinopsis).
Maso sundevalli Bösenberg, 1902: 154, pl. 13, f. 207 (mf).
Caseola herbicola Emerton, 1909: 186, pl. 2, f. 1 (Dmf) [urn:lsid:nmbe.ch:spidersp:058566].
Maso frontata Banks, 1911: 447, pl. 35, f. 17.
Minicia sundevalli Dahl, 1912b: 604.
Maso sundevalli Simon, 1926: 330, 478, f. 548-549 (mf).
Maso sundevalli Bishop & Crosby, 1935c: 233, pl. 19, f. 35-37 (mf, S of Caseola herbicola and Maso frontatus).
Maso sundevalli Miller, 1947: 37, pl. VI, f. 5 (f).
Maso sundevalli Kaston, 1948: 145, f. 346-350 (mf).
Maso sundevalli Locket & Millidge, 1953: 232, f. 133A, C, F (mf).
Maso sundevalli Brændegaard, 1958: 46, f. 37 (f).
Maso sundevalli Wiehle, 1960a: 20, f. 9-14 (mf).
Maso sundevalli Merrett, 1963b: 413, f. 89A-E (m).
Maso sundevalli Miller, 1971: 260, pl. LIII, f. 5-6 (mf).
Maso sundevalli Palmgren, 1976: 77, f. 3.4-6 (mf).
Maso sundevalli Millidge, 1977: 19, f. 63 (m).
Maso sundevalli Saito, 1979: 81, f. 2, 11, 15 (mf).
Maso sundevalli Matsuda, 1986: 88, f. 8 (f).
Maso sundevalli Roberts, 1987: 54, f. 20a (mf).
Maso sundevalli Tanasevitch, 1990: 108, f. 22.35, 24.46, 28.30 (mf).
Maso sundevalli Heimer & Nentwig, 1991: 208, f. 559 (mf).
Maso sundevalli Sha, Gao & Zhu, 1994: 17, f. 13-16 (mf).
Maso sundevalli Agnarsson, 1996: 88, f. 79A-B (mf).
Maso sundevalli Song, Zhu & Chen, 1999: 186, f. 104K-N (mf).
Maso sundevalli Paquin & Dupérré, 2003: 114, f. 1170-1172 (mf).
Maso sundevalli Ono, Matsuda & Saito, 2009: 260, f. 5-9 (mf).
Maso sundevalli Marusik & Kunt, 2009b: 85, f. 3-4 (f).
Maso sundevalli Zhu & Zhang, 2011: 131, f. 83A-D (mf).
Maso sundevalli Seo, 2011b: 144, f. 3A-G (mf).
Maso sundevalli Yin et al., 2012: 510, f. 238a-b (f).
Maso sundevalli Tilly & Tilly, 2019: 11, f. 10A-B (f).

Maso marxi matanuskae Chamberlin, 1949: 534 (Df).
Maso sundevallii matanuskae Buckle et al., 2001: 131.