Unio tetralasmus Say, 1831
Say, 1831. Amer. Conch. 3: pl. 23.
Type(s): TYPE LOST XXX_UNKNOWN, Bayou St. John, near New Orleans.

Unio (sec. Uniomerus) tetralasmus — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Uniomerus tetralasmus — Ortmann (1912), Utterback (1915), Murray & Leonard (1962), Haas (1969), Haas (1969), ... Dai et al. (2025), Chen et al. (2025), FMCS (2025), Cummings et al. (2025), Campbell & Lydeard (2026)
Elliptio (Uniomerus) tetralasmus — Frierson (1927), Haas (1929)
Elliptio (sec. Uniomerus) tetralasmus — Thiele (1934)
Uniomerus tretalasmus [sic] — Contreras-Arquieta (2000)
U. tetralasmus — Marshall et al. (2018)

Unio camptodon Say, 1832
Say, 1832. Amer. Conch. 5: pl. 42.
Type(s): TOPOTYPE USNM_85354, New Orleans, La.

Unio (sec. Uniomerus) tetralasmus var. camptodon — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Uniomerus tetralasmus comptodon [sic] — Utterback (1915)
Elliptio (Uniomerus) tetralasmus-camptodon — Frierson (1927)
Uniomerus tetralasmus — Murray & Leonard (1962), Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), R.I. Johnson (1980), Oesch (1984), Vidrine (1993), Howells et al. (1996), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio sayanus Conrad, 1838
‘Ward’ of Authors.
Conrad, 1838. Monogr. Fam. Unionidae 2(11): 102, pl. 56, fig. 2.
B.H. Wright, 1888. Check List N. Amer. Unionidae etc.: [5].
(error for Unio sayii Tappan, 1839)

Unio (sec. Uniomerus) tetralasmus var. sayi — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Elliptio (Uniomerus) tetralasmus-sayi — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), Parmalee & Bogan (1998), Williams et al. (2008)
Uniomerus declivis — Watters et al. (2009)

Unio sayii Tappan, 1839
Ward in Tappan, 1839. Amer. J. Sci. 35: 268, pl. 3, fig. 1.
Type(s): POSSIBLE SYNTYPE USNM_85356, Scioto R., Ohio.

Unio (sec. Uniomerus) tetralasmus var. sayi — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Uniomerus tetralasmus — Utterback (1915), Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), R.I. Johnson (1980), Oesch (1984), Howells et al. (1996), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)
Elliptio (Uniomerus) tetralasmus-sayi — Frierson (1927)
Uniomerus tetralasmus sayi — F.C. Baker (1928)

Unio parallelus Conrad, 1841
Conrad, 1841. Proc. Acad. Nat. Sci. 1: 20 [as ‘paralellus’].
Conrad, 1854. Jour. Acad. Nat. Sci. 2(4): 297 [as ‘parallelus’].
(renamed Unio porrectus Conrad, 1854; homonym of Unio parallelus Sowerby, 1840; correct name for Unio paralellus Conrad, 1841)

Unio (sec. Uniomerus) tetralasmus — Simpson (1900), Simpson (1914)
Elliptio (Uniomerus) tetralasmus — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio symmetricus Lea, 1845
Lea, 1845. Proc. Amer. Phil. Soc. 4: 164.
Lea, 1848. Trans. Amer. Phil. Soc. 10 [O. 4]: 73 [47], pl. 4, fig. 11.
Type(s): HOLOTYPE USNM_85604, Alexandria, La.

Unio (sec. Uniomerus) tetralasmus — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Elliptio (Uniomerus) tetralasmus — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Vidrine (1993), Howells et al. (1996), Parmalee & Bogan (1998), Williams et al. (2008)
Uniomerus declivis — Watters et al. (2009)

Unio rivularis Conrad, 1853
‘Say’ Conrad, 1836. Monogr. Fam. Unionidae 1(5): 45, pl. 23, fig. 1 [as ‘U. declivis’].
Conrad, 1853. Proc. Acad. Nat. Sci. 6: 257.
Conrad, 1854. Jour. Acad. Nat. Sci. 2(4): 296.
Type(s): HOLOTYPE ANSP_42852, small creek in Greene Co., Ala.

Unio (sec. Uniomerus) obesus — Simpson (1900), Simpson (1914)
Elliptio (Uniomerus) obesus — Frierson (1927)
Uniomerus obesus — Clench & Turner (1956), Haas (1969)
Uniomerus tetralasmus — R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio porrectus Conrad, 1854
Conrad, 1853. Proc. Acad. Nat. Sci. 6: 268. [nomen nudum]
Conrad, 1854. Jour. Acad. Nat. Sci. 2(4): 296, pl. 26, fig. 7.
(new name for Unio parallelus Conrad, 1841; homonym of Unio porrectus Sowerby, 1829)
Type(s): HOLOTYPE ANSP_42847, Jackson, Miss.

Unio (sec. Uniomerus) tetralasmus — Simpson (1900), Simpson (1914)
Elliptio (Uniomerus) tetralasmus — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio subcroceus Conrad, 1854
Conrad, 1853. Proc. Acad. Nat. Sci. 6: 268. [nomen nudum]
Conrad, 1854. Jour. Acad. Nat. Sci. 2(4): 297, pl. 27, fig. 1.
Type(s): HOLOTYPE ANSP_41406, Canadian Fork, Arkansas River.

Unio (sec. Uniomerus) tetralasmus — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Elliptio (Uniomerus) tetralasmus — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio manubius Gould, 1855
Gould, 1855. Proc. Boston Soc. Nat. Hist. 5: 229.
Type(s): LECTOTYPE MCZ_169447 (by R.I. Johnson, 1964: 108), Chihuahua, 60 mi from Camp Ringgold, Mexico.

Unio (sec. Uniomerus) tetralasmus var. manubius — Simpson (1900), Simpson (1914)
Unio (Uniomerus) manubius — Martens (1900)
Unio (s.s.) tetralasmus — Call (1900)
Elliptio (Uniomerus) tetralasmus-manubius — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Parmalee & Bogan (1998), R.I. Johnson (1999), Williams et al. (2008), Watters et al. (2009), Cummings et al. (2025)

Unio jamesianus Lea, 1857
Lea, 1857. Proc. Acad. Nat. Sci. 9: 84.
Lea, 1858. Jour. Acad. Nat. Sci. 4 [O. 6]: 52 [52], pl. 6, fig. 35.
Type(s): HOLOTYPE USNM_85365, Jackson, Miss.

Unio (sec. Uniomerus) tetralasmus — Simpson (1900), Simpson (1914)
Unio (s.s.) tetralasmus — Call (1900)
Elliptio (Uniomerus) tetralasmus — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Vidrine (1993), Howells et al. (1996), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio electrinus Reeve, 1865
Reeve, 1865. Conch. Icon. 16: pl. 25, sp. 121.

Unio (sec. Uniomerus) tetralasmus var. sayi — Simpson (1900), Simpson (1914)
Elliptio (Uniomerus) tetralasmus-sayi — Frierson (1927)
Uniomerus tetralasmus — Haas (1969), R.I. Johnson (1970), R.I. Johnson (1972), Burch (1975), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio manubrius Paetel, 1890
‘Gould’ of Authors.
Paetel, 1890. Cat. Conch.-Samml. 3: 158.
Call, 1895. Trans. Acad. Sci. St. Louis 7: 53.
Call, 1900. Ind. Dept. Geol. Nat. Res. (1899): 518.
(error for Unio manubius Gould, 1855)

Unio (sec. Uniomerus) tetralasmus var. manubius — Simpson (1900), Simpson (1914)
Uniomerus tetralasmus — Parmalee & Bogan (1998), Watters et al. (2009)

Uniomerus tetralasma comptodon Utterback, 1915
Utterback, 1915. Amer. Midl. Nat. 4(3): 48.
Utterback, 1915. Amer. Midl. Nat. 4(6): 247.
(error for Unio camptodon Say, 1832)

Uniomerus tetralasmus — Parmalee & Bogan (1998), Watters et al. (2009)

Unio declivis Conrad, 1836
‘Say’ Conrad, 1836. Monogr. Fam. Unionidae 1(5): 45, pl. 23, fig. 1.
Conrad, 1838. Monogr. Fam. Unionidae 2(11): back cover correginda [as ‘U. sayanus Ward’].
(misidentified reference to Unio declivis Say, 1831)

Unio (sec. Uniomerus) obesus — Simpson (1900), Simpson (1914)
Uniomerus tetralasmus — Utterback (1915), R.I. Johnson (1970), R.I. Johnson (1972), Parmalee & Bogan (1998), Watters et al. (2009)
Elliptio (Uniomerus) tetralasmus — Frierson (1927)

Unio paralellus Conrad, 1841
Conrad, 1841. Proc. Acad. Nat. Sci. 1: 20.
(incorrect original spelling of Unio parallelus Conrad, 1841)

Unio rhomboidius Lea, 1852
‘Ward MSS’ Lea, 1852. Synopsis Fam. Naiades: 32. [nomen nudum]
(intro'd as syn of Unio camptodon Say, 1832)

Unio camptodon Stearns, 1891
Stearns, 1891. Proc. U.S. Nat. Mus. 14 (844): 105.
(reference to Unio camptodon Say, 1832)

Unio (sec. Uniomerus) tetralasmus var. camptodon — Simpson (1900)

Unio electricus Haas, 1969
‘Reeve’ Haas, 1969. Das Tierreich 88: 209.
(error for Unio electrinus Reeve, 1865)

Uniomerus tretalasmus Contreras-Arquieta, 2000
‘Say’ Contreras-Arquieta, 2000. Mexicoa 2(1): 45.
(error for Unio tetralasmus Say, 1831)