Unio cuprinus Lea, 1831
Lea, 1831. Trans. Amer. Phil. Soc. 4 [O. 1]: 94, pl. 12, fig. 24.
Type(s): HOLOTYPE USNM_86121, Mexico.

Lampsilis (Proptera) metallicus — Simpson (1900)
Unio (Simonaias) cuprinus — Martens (1900)
Lampsilis (Proptera) metallica — Simpson (1914)
Elliptio (Popenaias) metallicus — Frierson (1927)
Nephronaias (Popenaias) metallica — Haas (1969)
— Inoue et al. (2020)

Unio metallicus Say, 1831
Say, 1831. New Harm. Dissem. 1(29): [no pagination].
Say, 1858. [in] Binney, Compl. Writings T. Say: 133.

Lampsilis (Proptera) metallicus — Simpson (1900)
Unio (Simonaias) cuprinus var. persulcatus — Martens (1900)
Lampsilis (Proptera) metallica — Simpson (1914)
Elliptio (Popenaias) metallicus — Frierson (1927)
Nephronaias (Popenaias) metallica — Haas (1969)
Popenaias metallica — Graf & Cummings (2007), Bogan (2010), Inoue et al. (2020), Graf & Cummings (2021), Czaja et al. (2023)

Unio aereus Reeve, 1865
Reeve, 1865. Conch. Icon. 16: pl. 30, sp. 160.

Lampsilis (Proptera) metallicus — Simpson (1900)
Lampsilis (Proptera) metallica — Simpson (1914)
Elliptio (Popenaias) metallicus — Frierson (1927)
Nephronaias (Popenaias) metallica — Haas (1969)

Unio (Simonaias) cuprinus subventralis Martens, 1900
Martens, 1900. Biol. Centr.-Amer., Moll.: 506, pl. 36, figs. 1-1b.
(intro'd as intra-sp. of Unio cuprinus Lea, 1831)
Type(s): TYPE ZMB_108852, Tabasco, Mexico.

Unio (Simonaias) cuprinus subventralis — Martens (1900)
Nephronaias calamitarum var. subventralis — Simpson (1914)
Elliptio (Nephronaias) subventralis — Frierson (1927)
Nephronaias (Popenaias) metallica — Haas (1969)

Unio cuprinus Sowerby, 1868
‘Lea’ Sowerby, 1868. Conch. Icon. 16: pl. 66, sp. 336.
(reference to Unio cuprinus Lea, 1831)

Unio (Simonaias) cuprinus var. nephritica [sic] — Martens (1900)
Lampsilis (Proptera) metallicus — Simpson (1900)
Lampsilis (Proptera) metallica — Simpson (1914)

Unio acreus Haas, 1969
‘Reeve’ Haas, 1969. Das Tierreich 88: 202.
(error for Unio aereus Reeve, 1865)