Genus Orthonychia Hall, 1843[3]
- Orthonychia acuta Roemer, 1856
- Orthonychia baldwini Rohr et al., 1981
- Orthonychia belli Clarke, 1908
- Orthonychia bowsheri Yochelson, 1956
- Orthonychia chesterense Meek & Worthen, 1866
- Orthonychia concavum Hall, 1860
- Orthonychia conicum Hall, 1860
- Orthonychia conoidea (Goldfuss, 1844)
- Orthonychia cornuforme (Winchell, 1863)
- Orthonychia costata (Barrois, 1889)
- Orthonychia daschi (Rohr & Smith, 1978)
- Orthonychia dentalium Hall, 1862
- Orthonychia enorme (Lindström, 1884)
- Orthonychia infabricatus Hyde, 1953
- Orthonychia marblecreekensis Talent & Philip, 1956
- Orthonychia obliquesulata Spitz, 1907
- Orthonychia pajerensis Chronic, 1949
- Orthonychia parva (Shumard & Swallow, 1858)
- Orthonychia parvulum Whiteaves, 1892
- Orthonychia pentalvea Talent & Philip, 1956
- Orthonychia perplexum (Hall, 1879)
- Orthonychia prosseri Clarke & Swartz, 1913
- Orthonychia protei (Oehlert, 1883)[1]
- Orthonychia puellaris (Whidborne, 1891)
- Orthonychia quadrangularis (Whidborne, 1891)
- Orthonychia rostratus (Trenkner, 1867)
- Orthonychia sciotoensis Hyde, 1953
- Orthonychia sileni (Oehlert, 1883)
- Orthonychia subrectum Hall, 1860 - type species
- Orthonychia steinbergensis Kegel, 1926
- Orthonychia talon Tolmachoff, 1930
- Orthonychia tortuosa (Hall, 1860)
- Orthonychia trirotundolobatum (Talent & Philip, 1956)
- Orthonychia unguiculata Clarke & Swartz, 1913
- Orthonychia variablis Tyler, 1965
- Orthonychia vishtytica Saladzius, 1966
- Orthonychia vomerium (Winchell, 1863)
- Orthonychia waverlyensis Hyde, 1953
- Orthonychia compressa / Platyceras (Orthonychia) compressum Girty 1910[4]
- Orthonychia ungula / Platyceras (Orthonychia) ungula (Weller, 1906)[5]
