Genera
Genus Orthonychia Hall, 1843 • 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) • 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 • Orthonychia ungula / Platyceras (Orthonychia) ungula (Weller, 1906) ==References==