Obliquaria (Quadrula) quadrula Rafinesque, 1820
Rafinesque, 1820. Ann. Gén. Sci. Phys. 5 (13): 307 [also as ‘Unio quadrula’].
Rafinesque, 1864. [in] Binney & Tryon, reprint: 51.
Type(s): NEOTYPE ANSP_20224 (by Johnson & Baker, 1973: 167), Salt River.

— Simpson (1900), Simpson (1914), de Gregorio (1914)
Quadrula quadrula — Utterback (1915), Vanatta (1915), Ortmann & Walker (1922), Ortmann (1924), Ortmann (1925), ... Dai et al. (2025), Freeman et al. (2025), Chen et al. (2025), FMCS (2025), Cummings et al. (2025)
Quadrula (s.s.) quadrula — Frierson (1927), F.C. Baker (1928), Haas (1969)
Quadrula (s.s.) gigantea [sic] — Haas (1930)
Quadrula (s.s.) quadrula quadrula — Haas (1969)
Obliquaria quadrula — Burch (1975)
Quadrula quedrula [sic] — Contreras-Arquieta (2000)
Quadrula quadrula quadrula — ITIS (2012)
Q. quadrula — Sheng et al. (2014)

Unio rugosus Barnes, 1823
Barnes, 1823. Amer. J. Sci. 6 (1-2): 126, pl. 8, fig. 9a-b.

— Simpson (1914)
Quadrula quadrula — Ortmann & Walker (1922), Burch (1975), R.I. Johnson (1980), Parmalee & Bogan (1998), Williams et al. (2008), Lopes-Lima et al. (2019)
Quadrula (s.s.) quadrula — Frierson (1927), F.C. Baker (1928)
Quadrula (s.s.) gigantea [sic] — Haas (1930)
Quadrula (s.s.) quadrula quadrula — Haas (1969)
Quadrula fragosa — Watters et al. (2009)

Unio lacrymosus Lea, 1828
Lea, 1828. Trans. Amer. Phil. Soc. 3 [O. 1]: 272 [14], pl. 6, fig. 8.
Type(s): HOLOTYPE USNM_84165, Cincinnati, Ohio.

Quadrula (sec. Theliderma) lachrymosa [sic] — Simpson (1900), Simpson (1914)
Unio (s.s.) lachrymosus [sic] — Call (1900)
Quadrula lachrymosus [sic] — Ortmann (1909)
Quadrula lachrymosa [sic] — Ortmann (1909), Ortmann (1910), Ortmann (1910), Ortmann (1912)
— de Gregorio (1914)
Quadrula quadrula — Utterback (1915), Vanatta (1915), Ortmann & Walker (1922), Burch (1975), R.I. Johnson (1980), ... Strayer & Jirka (1997), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009), Lopes-Lima et al. (2019)
Quadrula (s.s.) quadrula — Frierson (1927), F.C. Baker (1928)
Quadrula (s.s.) quadrula quadrula — Haas (1969)

Unio apiculatus Say, 1829
Say, 1829. New Harm. Dissem. 2(20): 309, sp. 8.
Say, 1834. Amer. Conch. 6: pl. 52.
Say, 1858. [in] Binney, Compl. Writings T. Say: 131, 207, 225.
Type(s): TYPE LOCALITY TYPE_LOCALITY_MP_016, Lake Ponchartrain, near N. Orleans.

Quadrula (sec. Theliderma) apiculata — Simpson (1900), Simpson (1914)
Quadrula apiculata — Ortmann (1910), R.I. Johnson (1980), Davis & Fuller (1981), Turgeon et al. (1988), Williams et al. (1993), ... Marshall et al. (2018), Pfeiffer et al. (2019), Pfeiffer et al. (2019), Inoue et al. (2020), Hauck et al. (2023)
— de Gregorio (1914)
Quadrula (s.s.) quadrula-apiculata — Frierson (1927)
Quadrula (s.s.) quadrula apiculata — Haas (1969)
Quadrula quadrula — Burch (1975), Lopes-Lima et al. (2019), Graf & Cummings (2021), FMCS (2021), Keogh et al. (2024), FMCS (2025), Cummings et al. (2025)

Unio asper Lea, 1831
Lea, 1831. Trans. Amer. Phil. Soc. 4 [O. 1]: 85 [95], pl. 9, fig. 15.
Type(s): UNKNOWN USNM_84212, Claiborne, Ala. R., Alabama.

Quadrula (sec. Theliderma) asper — Simpson (1900)
Quadrula aspera — Ortmann (1912), Utterback (1915)
Quadrula (sec. Theliderma) aspera — Simpson (1914)
— de Gregorio (1914)
Quadrula (s.s.) quadrula-aspera — Frierson (1927)
Quadrula (s.s.) quadrula aspera — Haas (1969)
Quadrula quadrula — Burch (1975), R.I. Johnson (1980), Vidrine (1993), Lopes-Lima et al. (2019)
Quadrula apiculata — Williams et al. (2008)

Unio asperrimus Lea, 1831
Lea, 1831. Trans. Amer. Phil. Soc. 4 [O. 1]: 71 [81], pl. 5, fig. 3.
Type(s): HOLOTYPE USNM_84174, Cincinnati, Ohio.

Quadrula (sec. Theliderma) lachrymosa [sic] — Simpson (1900), Simpson (1914)
Unio (s.s.) lachrymosus [sic] — Call (1900)
Unio asperrimus — de Gregorio (1914)
Quadrula quadrula — Utterback (1915), Ortmann & Walker (1922), 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), Lopes-Lima et al. (2019)
Quadrula (s.s.) quadrula — Frierson (1927), F.C. Baker (1928)
Quadrula (s.s.) quadrula quadrula — Haas (1969)

Unio quadrulus Say, 1834
‘Rafinesque’ of Authors.
Say, 1834. Amer. Conch. 6: pl. 53.
Conrad, 1840. Monogr. Fam. Unionidae 2(13): 112, pl. 62.

Quadrula (sec. Theliderma) lachrymosa [sic] — Simpson (1900), Simpson (1914)
Quadrula quadrula — Utterback (1915), Watters et al. (2009)

Quadrula lachrymosa Swainson, 1840
‘Lea’ of Authors.
Swainson, 1840. Treat. Malacol.: 378.
Hanley, 1843. Illustr. Descr. Cat. Rec. Bivalve Shells: 177.
Conrad, 1853. Proc. Acad. Nat. Sci. 6: 256.
Adams & Adams, 1857. Gen. Rec. Moll. 2(31-32): 497.
Reeve, 1864. Conch. Icon. 16: pl. 9, sp. 33.
Call, 1895. Trans. Acad. Sci. St. Louis 7: 21.
F.C. Baker, 1898. Bull. Chicago Acad. Sci. 3(1): 83, pl. 25, fig. 1; pl. 12, fig. 2.
Simpson, 1900. Proc. U.S. Nat. Mus. 22: 776.
Call, 1900. Ind. Dept. Geol. Nat. Res. (1899): 489.
Ortmann, 1909. Nautilus 22(10): 100.
Ortmann, 1909. Ann. Carnegie Mus. 5: 199.
Ortmann, 1910. Nautilus 23(11): 140.
Ortmann, 1910. Nautilus 23: 116.
Ortmann, 1912. Ann. Carnegie Mus. 8: 253.
Simpson, 1914. Descr. Cat. Naiades: 839, 841.
Vanatta, 1915. Proc. Acad. Nat. Sci. 67: 556.
Ortmann & Walker, 1922. Occ. Pap. Mus. Zool. Univ. Mich. (112): 14, 16.
Frierson, 1927. Check List N. Amer. Naiades: 47.
F.C. Baker, 1928. Bull. Wisconsin Geol. Nat. Hist. Survey 70(2): 84.
R.I. Johnson, 1980. Bull. MCZ 149(2): 90.
Vidrine, 1993. Histr. Distr. Freshw. Mussels LA: 53.
Strayer & Jirka, 1997. Pearly Mussels NY (26): 98.

Quadrula quadrula — Utterback (1915), Murray & Leonard (1962), Oesch (1984), Vidrine (1993), Parmalee & Bogan (1998), Watters et al. (2009)

Unio rumphianus Lea, 1852
Lea, 1852. Trans. Amer. Phil. Soc. 10 [O. 5]: 276 [32], pl. 22, fig. 34.
Lea, 1852. Proc. Amer. Phil. Soc. 5: 252. [nomen nudum]
Type(s): HOLOTYPE USNM_84189, West Georgia.

Quadrula (sec. Theliderma) rumphiana — Simpson (1900), Simpson (1914)
Quadrula (s.s.) quadrula-rumphiana — Frierson (1927)
Quadrula (s.s.) quadrula rumphiana — Haas (1969)
Quadrula quadrula — Burch (1975), Lopes-Lima et al. (2019), Graf & Cummings (2021), FMCS (2021), FMCS (2025)
Quadrula rumphiana — Turgeon et al. (1988), Williams et al. (1993), Turgeon et al. (1998), Lydeard et al. (1999), Serb et al. (2003), ... Haag (2012), Williams et al. (2017), Inoue et al. (2018), Burlakova et al. (2019), Hauck et al. (2023)
Quadrula quadrula rumphiana — Keogh et al. (2024)

Unio blandianus Lea, 1857
Lea, 1857. Proc. Acad. Nat. Sci. 8: 263.
Lea, 1857. Proc. Acad. Nat. Sci. 9: 31.
Lea, 1858. Jour. Acad. Nat. Sci. 4 [O. 6]: 65, pl. 11, fig. 47.
Type(s): HOLOTYPE USNM_84190, Othcaloosa Cr., Ga.

Quadrula (sec. Theliderma) rumphiana — Simpson (1900), Simpson (1914)
Quadrula (s.s.) quadrula-rumphiana — Frierson (1927)
Quadrula (s.s.) quadrula rumphiana — Haas (1969)
Quadrula quadrula — Burch (1975), Lopes-Lima et al. (2019)
Quadrula rumphiana — Williams et al. (2008)

Unio forsheyi Lea, 1859
Lea, 1859. Proc. Acad. Nat. Sci. 11: 155.
Lea, 1860. Jour. Acad. Nat. Sci. 4 [O. 8]: 357 [39], pl. 60, fig. 182.
Type(s): LECTOTYPE [AS HOLOTYPE] USNM_84169 (by R.I. Johnson, 1974: 59), Texas.

Quadrula (sec. Theliderma) forsheyi — Simpson (1900), Simpson (1914)
Quadrula forsheyi — Ortmann (1910)
Quadrula (s.s.) quadrula-forsheyi — Frierson (1927)
Quadrula (s.s.) quadrula forsheyi — Haas (1969)
Quadrula quadrula — Burch (1975), Howells et al. (1996), Lopes-Lima et al. (2019), Cummings et al. (2025)
Quadrula apiculata — Williams et al. (2008)

Unio speciosus Lea, 1862
Lea, 1862. Proc. Acad. Nat. Sci. 14: 168.
Lea, 1862. Jour. Acad. Nat. Sci. 5 [O. 9]: 207 [29], pl. 31, fig. 276.
Type(s): LECTOTYPE [AS HOLOTYPE] USNM_84172 (by R.I. Johnson, 1974: 134), Leon Co., Texas.

Quadrula (sec. Theliderma) speciosa — Simpson (1900), Simpson (1914)
Quadrula speciosa — Ortmann (1910)
— de Gregorio (1914)
Quadrula (s.s.) quadrula-speciosa — Frierson (1927)
Quadrula (s.s.) quadrula speciosa — Haas (1969)
Quadrula quadrula — Burch (1975), Cummings et al. (2025)
Quadrula apiculata — R.I. Johnson (1999)

Unio quadratus Reeve, 1864
‘Rafinesque’ Reeve, 1864. Conch. Icon. 16: pl. 6, sp. 24.

Quadrula (sec. Theliderma) lachrymosa [sic] — Simpson (1900), Simpson (1914)
Quadrula (s.s.) quadrula — Frierson (1927)
Quadrula (s.s.) quadrula quadrula — Haas (1969)
Quadrula quadrula — Parmalee & Bogan (1998), Watters et al. (2009)

Unio turgidus Reeve, 1864
‘Lea’ Reeve, 1864. Conch. Icon. 16: pl. 3, sp. 10.

Quadrula (sec. Theliderma) asper — Simpson (1900)
Quadrula (sec. Theliderma) aspera — Simpson (1914)

Unio lunulatus Pratt, 1876
Pratt, 1876. Proc. Davenport Acad. Nat. Sci. 1: 168, pl. 31, fig. 1a-b [as ‘unul atus’; corrected in Errata].

Quadrula (sec. Theliderma) lachrymosa [sic] var. lunulata — Simpson (1900)
Tritogonia nobilis — Simpson (1914)
Quadrula (s.s.) quadrula — Frierson (1927)
Quadrula (s.s.) quadrula quadrula — Haas (1969)
Quadrula quadrula — Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009), Lopes-Lima et al. (2019)

Quadrula quadrula contraryensis Utterback, 1915
Utterback, 1915. Amer. Midl. Nat. 4(4): 138, pl. 18, figs. 47a-b.
Type(s): NEOTYPE CM_61.6892 (by Parodiz & Tripp, 1988: 118), Lake Contrary, St. Joseph, Buchanan Co., Missouri.

Quadrula quadrula contraryensis — Utterback (1915)
Quadrula quadrula — Burch (1975), R.I. Johnson (1980), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009), Lopes-Lima et al. (2019)

Quadrula (Quadrula) quadrula bullocki F.C. Baker, 1928
F.C. Baker, 1928. Bull. Wisconsin Geol. Nat. Hist. Survey 70(2): 87, pl. 46, figs. 1-3.
Type(s): HOLOTYPE (ORIG. DESIG.) UMMZ_209203, Fox River, nr. De Pere, Wisc.

Quadrula (s.s.) quadrula bullocki — F.C. Baker (1928)
Quadrula quadrula — Clarke (1973), Burch (1975), R.I. Johnson (1980), Parmalee & Bogan (1998), Williams et al. (2008), Watters et al. (2009), Lopes-Lima et al. (2019)

Unio dombeyanus Barnes, 1828
Barnes, 1828. Amer. J. Sci. 13(2): 360.

Quadrula (s.s.) quadrula — Frierson (1927)

Unio asperimus Ravenel, 1834
‘Lea’ Ravenel, 1834. Cat. Rec. Shells: 5.

Unio asper Jay, 1839
‘Lea’ Jay, 1839. Cat. Rec. Shells: 55.

Unio nobilis Conrad, 1854
Conrad, 1854. Jour. Acad. Nat. Sci. 2(4): 297, pl. 27, figs. 2. [in part]

Quadrula (sec. Theliderma) apiculata — Simpson (1900), Simpson (1914)
— de Gregorio (1914)
Quadrula nobilis — Utterback (1915)
Quadrula quadrula — Burch (1975), R.I. Johnson (1980), Howells et al. (1996)
Quadrula apiculata — Vidrine (1993), Parmalee & Bogan (1998)

Unio unul atus Pratt, 1876
Pratt, 1876. Proc. Davenport Acad. Nat. Sci. 1: 168.

Quadrula quadrula — Lopes-Lima et al. (2019)

Quadrula (s.s.) gigantea Haas, 1930
‘Raf.’ Haas, 1930. Senckenbergiana 12(6): 327.

Quadrula contrayensis R.I. Johnson, 1969
‘Utterback’ R.I. Johnson, 1969. Nautilus 82(4): 132.

Quadrula quadrula — Parmalee & Bogan (1998)

Quadrula quedrula Contreras-Arquieta, 2000
‘Rafinesque’ Contreras-Arquieta, 2000. Mexicoa 2(1): 44.