1. Species Orthoceras albersi S. A. Miller, 1894 †
2. Species Orthoceras regulare (Schlotheim, 1820) †
3. Subgenus Orthoceras (Campyloceras) M'Coy, 1844 † accepted as Campyloceras McCoy, 1844 † (unaccepted > superseded rank)
4. Subgenus Orthoceras (Trigonoceras) M'Coy, 1844 † accepted as Trigonoceras M'Coy, 1844 † (unaccepted > superseded rank)
5. Species Orthoceras adamsi Butts, 1926 † accepted as Buttsoceras adamsi (Butts, 1926) † (unaccepted > superseded combination)
6. Species Orthoceras attavus Brøgger, 1882 † accepted as Slemmestadoceras attavus (Brøgger, 1882) † (unaccepted > superseded combination)
7. Species Orthoceras atticus Billings, 1865 † accepted as Oxfordoceras atticus (Billings, 1865) † (unaccepted > superseded combination)
8. Species Orthoceras avelinii Salter, 1854 † accepted as Michelinoceras avelinii (Salter, 1854) † (unaccepted > superseded combination)
9. Species Orthoceras brainerdi Whitfield, 1886 † accepted as Proterocameroceras brainerdi (Whitfield, 1886) † (unaccepted > superseded combination)
10. Species Orthoceras caereesiense Hicks, 1875 † accepted as Michelinoceras avelinii (Salter, 1854) † (unaccepted > junior subjective synonym)
11. Species Orthoceras cataline Billings, 1865 † accepted as Ectocycloceras cataline (Billings, 1865) † (unaccepted > superseded combination)
12. Species Orthoceras chinianense Thoral, 1935 † accepted as Saloceras chinianense (Thoral, 1935) † (unaccepted > superseded combination)
13. Species Orthoceras clathratoannulatum Roemer, 1861 † accepted as Gorbyoceras clathratoannulatum (Roemer, 1861) † (unaccepted > superseded combination)
14. Species Orthoceras conicum J. De C. Sowerby, 1839 † accepted as Armenoceras subconicum (A. d'Orbigny, 1850) † (unaccepted > junior homonym, invalid: junior homonym of Orthoceratites conicus Hisinger, 1837; Orthoceratites subconicus is a replacement name)
15. Species Orthoceras coreanicum Kobayashi, 1928 † accepted as Holmiceras coreanicum (Kobayashi, 1928) † (unaccepted > superseded combination)
16. Species Orthoceras cornuoryx Whitfield, 1886 † accepted as Rudolfoceras cornuoryx (Whitfield, 1886) † (unaccepted > superseded combination)
17. Species Orthoceras elegans Münster, 1841 † accepted as Trematoceras elegans (Münster, 1841) † (unaccepted > superseded combination)
18. Species Orthoceras escandei Thoral, 1935 † accepted as Rioceras escandei (Thoral, 1935) † (unaccepted > superseded combination)
19. Species Orthoceras estivali Thoral, 1935 † accepted as Saloceras chinianense (Thoral, 1935) † (unaccepted > junior subjective synonym)
20. Species Orthoceras explorator Billings, 1865 † accepted as Cyptendocerina explorator (Billings, 1865) † (unaccepted > superseded combination)
21. Species Orthoceras festinans Blake, 1882 † accepted as Dideroceras festinans (Blake, 1882) † (unaccepted > superseded combination, original combination)
22. Species Orthoceras formosum Billings, 1857 † accepted as Ephippiorthoceras formosum (Billings, 1857) † (unaccepted > superseded combination)
23. Species Orthoceras gorbyi S. A. Miller, 1894 † accepted as Gorbyoceras gorbyi (S. A. Miller, 1894) † (unaccepted > superseded combination)
24. Species Orthoceras knoxense McChesney, 1859 † accepted as Pseudorthoceras knoxense (McChesney, 1859) † (unaccepted > superseded combination)
25. Species Orthoceras lamarcki Billings, 1859 † accepted as Protocycloceras lamarcki (Billings, 1859) † (unaccepted > superseded combination)
26. Species Orthoceras laqueatum Hall, 1847 † accepted as Kionoceras laqueatum (Hall, 1847) † (unaccepted > superseded combination)
27. Species Orthoceras luhai Stumbur, 1956 † accepted as Isorthoceras luhai (Stumbur, 1956) † (unaccepted > superseded combination)
28. Species Orthoceras makkolense Kobayashi, 1928 † accepted as Sactorthoceras makkolense (Kobayashi, 1928) † (unaccepted > superseded combination)
29. Species Orthoceras martyi Thoral, 1935 † accepted as Annbactroceras martyi (Thoral, 1935) † (unaccepted > superseded combination)
30. Species Orthoceras mendax Salter, 1859 † accepted as Protocycloceras mendax (Salter, 1859) † (unaccepted > superseded combination)
31. Species Orthoceras michelini Barrande, 1866 † accepted as Michelinoceras michelini (Barrande, 1866) † (unaccepted > superseded combination, original combination)
32. Species Orthoceras montrealense Billings, 1859 † accepted as Clitendoceras montrealense (Billings, 1859) † (unaccepted > superseded combination)
33. Species Orthoceras mourguesi Thoral, 1935 † accepted as Bactroceras mourguesi (Thoral, 1935) † (unaccepted > superseded combination)
34. Species Orthoceras nummularium J. De C. Sowerby, 1839 † accepted as Armenoceras nummularium (J. De C. Sowerby, 1839) † (unaccepted > superseded combination)
35. Species Orthoceras perseus Billings, 1865 † accepted as Bassleroceras perseus (Billings, 1865) † (unaccepted > superseded combination)
36. Species Orthoceras pradense Thoral, 1935 † accepted as Saloceras pradense (Thoral, 1935) † (unaccepted > superseded combination)
37. Species Orthoceras repens Billings, 1865 † accepted as Protocycloceras repens (Billings, 1865) † (unaccepted > superseded combination)
38. Species Orthoceras reticulatum Hauer, 1847 † accepted as Dictyoconites doylei Riegraf, 1998 † (unaccepted > junior homonym, invalid: not Phillips, 1836; D. doylei is a replacement name)
39. Species Orthoceras rudis J. Hall, 1859 † accepted as Anastomoceras rudis (J. Hall, 1859) † (unaccepted > superseded combination)
40. Species Orthoceras sayi Billings, 1865 † accepted as Pachendoceras sayi (Billings, 1865) † (unaccepted > superseded combination)
41. Species Orthoceras sceptrum Hall, 1888 † accepted as Sceptrites sceptrum (Hall, 1888) † (unaccepted > superseded combination)
42. Species Orthoceras sericeum Salter, 1866 † accepted as Saloceras sericeum (Salter, 1866) † (original combination)
43. Species Orthoceras spissum Hall, 1879 † accepted as Adnatoceras spissum (Hall, 1879) † (unaccepted > superseded combination)
44. Species Orthoceras subcampanile Kiparisova, 1954 † accepted as Trematoceras subcampanile (Kiparisova, 1954) † (unaccepted > superseded combination)
45. Species Orthoceras textumaraneum Roemer, 1861 † accepted as Gorbyoceras textumaraneum (Roemer, 1861) † (unaccepted > superseded combination)
46. Species Orthoceras thyestes Hall, 1879 † accepted as Petryoceras thyestes (Hall, 1879) † (unaccepted > superseded combination)
47. Species Orthoceras tricamerae H. J. Smith, 1938 † accepted as Arbuckleoceras tricamerae (H. J. Smith, 1938) † (unaccepted > superseded combination)
48. Species Orthoceras tyronense Foerste, 1912 † accepted as Centroonoceras tyronense (Foerste, 1912) † (unaccepted > superseded combination)
49. Species Orthoceras unicamera H. J. Smith, 1938 † accepted as Smithorthoceras unicamera (H. J. Smith, 1938) † (unaccepted > superseded combination)
50. Species Orthoceras veterator Billings, 1865 † accepted as Cyptendoceras veterator (Billings, 1865) † (unaccepted > superseded combination)
51. Species Orthoceras xerxes Billings, 1865 † accepted as Protocycloceras xerxes (Billings, 1865) † (unaccepted > superseded combination)
52. Subgenus Orthoceras (Loxoceras) M'Coy, 1844 † (uncertain > unassessed)
    1. Species Orthoceras (Loxoceras) distans M'Coy, 1844 † (uncertain > unassessed)
    2. Species Orthoceras (Loxoceras) incomitatum M'Coy, 1844 † (uncertain > unassessed)
53. Species Orthoceras annulocostatum Meek & Worthen, 1861 † (uncertain > unassessed)
54. Species Orthoceras arenosum J. Hall, 1859 † (uncertain > unassessed)
55. Species Orthoceras austriacum Mojsisovics, 1873 † (uncertain > unassessed)
56. Species Orthoceras beauportense Whiteaves, 1898 † (uncertain > unassessed)
57. Species Orthoceras berendtii Dewitz, 1880 † (uncertain > unassessed)
58. Species Orthoceras celticum Mojsisovics, 1873 † (uncertain > unassessed)
59. Species Orthoceras clavatum J. Hall, 1859 † (uncertain > unassessed)
60. Species Orthoceras heidelbergiae J. Hall, 1859 † (uncertain > unassessed)
61. Species Orthoceras indianum H. J. Smith, 1938 † (uncertain > unassessed)
62. Species Orthoceras isogramma Meek, 1871 † (uncertain > unassessed)
63. Species Orthoceras kinnekullense Foord, 1887 † (uncertain > unassessed)
64. Species Orthoceras latiseptatum Hauer, 1846 † (uncertain > unassessed)
65. Species Orthoceras liaotungense Endo, 1932 † (uncertain > unassessed)
66. Species Orthoceras longicameratum J. Hall, 1859 † (uncertain > unassessed)
67. Species Orthoceras ludlowense S. A. Miller & C. L. Faber, 1894 † (uncertain > unassessed)
68. Species Orthoceras magnichinense Endo, 1932 † (uncertain > unassessed)
69. Species Orthoceras menelaus Billings, 1862 † (uncertain > unassessed)
70. Species Orthoceras mucronatum M'Coy, 1844 † (uncertain > unassessed)
71. Species Orthoceras multilabiatum Hauer, 1888 † (uncertain > unassessed)
72. Species Orthoceras ortoni Meek, 1872 † (uncertain > unassessed)
73. Species Orthoceras pauciseptum J. Hall, 1859 † (uncertain > unassessed)
74. Species Orthoceras perparvum Billings, 1862 † (uncertain > unassessed)
75. Species Orthoceras perstriatum J. Hall, 1859 † (uncertain > unassessed)
76. Species Orthoceras politum McCoy, 1851 † (uncertain > unassessed)
77. Species Orthoceras rectiseptatum Endo, 1932 † (uncertain > unassessed)
78. Species Orthoceras revalense Foord, 1887 † (uncertain > unassessed)
79. Species Orthoceras rigidum J. Hall, 1859 † (uncertain > unassessed)
80. Species Orthoceras salinarium Hauer, 1846 † (uncertain > unassessed)
81. Species Orthoceras sandlingense Mojsisovics, 1873 † (uncertain > unassessed)
82. Species Orthoceras styriacum Mojsisovics, 1873 † (uncertain > unassessed)
83. Species Orthoceras subtextile J. Hall, 1859 † (uncertain > unassessed)
84. Species Orthoceras sulcatulum M'Coy, 1844 † (uncertain > unassessed)
85. Species Orthoceras tenuiannulatum J. Hall, 1859 † (uncertain > unassessed)
86. Species Orthoceras toyamai Endo, 1932 † (uncertain > unassessed)
87. Species Orthoceras triadicum Mojsisovics, 1873 † (uncertain > unassessed)
88. Species Orthoceras westoni Whiteaves, 1898 † (uncertain > unassessed)

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