Obliquaria (Quadrula) cyphya Rafinesque, 1820
Rafinesque, 1820. Ann. Gén. Sci. Phys. 5 (13): 305 [also as ‘U. cyphia’].
Rafinesque, 1864. [in] Binney & Tryon, reprint: 49.
(correct name for Unio cyphia Rafinesque, 1820)
Type(s): LECTOTYPE ANSP_20239, River Ohio.

— Simpson (1900), Simpson (1914)
Unio (s.s.) cyphyus — Call (1900)
Pleurobema cyphya — Vanatta (1915)
Plethobasus cyphyus — Ortmann (1918), Ortmann & Walker (1922), Ortmann (1924), Ortmann (1925), F.C. Baker (1928), ... Smith et al. (2020), Klymus et al. (2020), Graf & Cummings (2021), FMCS (2021), Hopper et al. (2023)
Pleurobema (Plethobasus) cyphyum — Frierson (1927)
Plethobasus cyphus [sic] — Campbell et al. (2005)

Unio cyphia Rafinesque, 1820
Rafinesque, 1820. Ann. Gén. Sci. Phys. 5 (13): 305.
(incorrect original spelling of Obliquaria (Quadrula) cyphya Rafinesque, 1820)

Pleurobema (sec. Plethobasus) aesopus — Simpson (1900), Simpson (1914)
Plethobasus aesopus — Utterback (1915)
Plethobasus cyphyus — Ortmann & Walker (1922), Oesch (1984), Watters et al. (2009)

Unio aesopus Green, 1827
Green, 1827. Contrib. Maclurian Lyceum 1: 46, fig. 3.

Pleurobema (sec. Plethobasus) aesopus — Simpson (1900), Simpson (1914)
Unio (s.s.) cyphyus — Call (1900)
Pleurobema aesopus — Ortmann (1909), Ortmann (1910)
Pleurobema æsopus — Ortmann (1909)
Plethobasus aesopus — Ortmann (1912), Utterback (1915), Thiele (1934)
— de Gregorio (1914)
Pleurobema cyphya — Vanatta (1915)
Plethobasus cyphyus — Ortmann & Walker (1922), F.C. Baker (1928), Murray & Leonard (1962), Haas (1969), Haas (1969), ... Graf & Cummings (2007), Williams et al. (2008), Watters et al. (2009), Campbell & Lydeard (2012), Graf & Cummings (2021)
Pleurobema (Plethobasus) cyphyum — Frierson (1927)

Unio compertus Frierson, 1911
Frierson, 1911. Nautilus 25(5): 53, pl. 3, middle & lower figs.
Type(s): LECTOTYPE UMMZ_80525 (by R.I. Johnson, 1972: 142), Holston River, Tennessee.

Pleurobema (sec. Plethobasus) compertum — Simpson (1914)
Plethobasus cyphyus compertus — Ortmann (1918), Ortmann (1924)
Pleurobema (Plethobasus) compertum — Frierson (1927)
Plethobasus compertus — Haas (1969)
Plethobasus cyphyus — R.I. Johnson (1980), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009)

Unio cicatricosus Conrad, 1834
‘Say’ Conrad, 1834. New Fresh-Water Shells: ??.
‘Say’ Conrad, 1840. Monogr. Fam. Unionidae 2(13): 115, pl. 64.
(misidentified reference to Unio cicatricosus Say, 1829)

Unio scyphius Küster, 1861
‘Rafinesque’ Küster, 1861. Conchyl. Cab. 9(2): 181.
(error for Obliquaria (Quadrula) cyphya Rafinesque, 1820)

Pleurobema (sec. Plethobasus) aesopus — Simpson (1900), Simpson (1914)
Pleurobema (Plethobasus) cyphyum — Frierson (1927)
Plethobasus cyphyus — Haas (1969), Parmalee & Bogan (1998), Watters et al. (2009)

Unio varicosus Lewis, 1871
‘Lea’ Lewis, 1871. Amer. J. Conch. 6: 219.
(misidentified reference to Unio varicosus Lea, 1831)

Plethobasus cyphyus compertus — Ortmann (1918)

Unio esopus de Gregorio, 1914
‘Green’ de Gregorio, 1914. Il Nat. Siciliano 2: 58.
(error for Unio aesopus Green, 1827)

Plethobasus cyphus Campbell et al., 2005
‘Rafinesque’ Campbell et al., 2005. Invert. Biol. 124(2): 154.
(error for Obliquaria (Quadrula) cyphya Rafinesque, 1820)