After Froese & Pauly, 2001 [“The Fishbase”]

<==o Catostomus Eoc. R. As. Mioc.-Plioc. Pleist. R. NA. [24]
   |-- C. ardens Jordan & Gilbert, 1881 (Utah sucker)
   |-- C. bernardini Girard, 1856 (Yaqui sucker)
   |-- C. cahita Siebert & Minckley, 1986 (Cahita sucker)
   |--o C. catostomus
   |  |-- C. c. catostomus (Forster, 1773) (Longnose sucker)
   |  `-- C. c. lacustris Bajkov, 1927 (Jasper longnose sucker)
   |-- C. clarkii Baird & Girard, 1854 (Desert sucker)
   |-- C. columbianus (Eigenmann & Eigenmann, 1893) (Bridgelip sucker)
   |-- C. commersoni (Lacépède, 1803) (White sucker)
   |-- C. conchos Meek, 1902
   |--o C. discobolus Cope, 1871 (Bluehead sucker)
   |  |-- C. d. discobolus Cope, 1871 (Bluehead sucker)
   |  `-- C. d. yarrowi (Cope, 1874) (Zuni bluehead sucker)
   |-- C. fumeiventris Miller, 1973 (Owens sucker)
   |-- C. insignis Baird & Girard, 1854 (Sonora sucker)
   |-- C. latipinnis Baird & Girard, 1853 (Flannelmouth sucker)
   |-- C. leopoldi Siebert & Minckley, 1986 (Bavispe sucker)
   |-- C. macrocheilus Girard, 1856 (Largescale sucker)
   |-- C. microps Rutter, 1908 (Modoc sucker)
   |--o C. occidentalis Ayres, 1854 (Sacramento sucker)
   |  |-- C. o. occidentalis Ayres, 1854 (Sacramento sucker)
   |  `-- C. o. lacusanserinus Fowler, 1913 (Goose lake sucker)
   |-- C. platyrhynchus (Cope, 1874) (Mountain sucker)
   |-- C. plebeius Baird & Girard, 1854 (Rio Grande sucker)
   |-- C. rimiculus Gilbert & Snyder, 1898 (Jenny creek sucker)
   |-- C. santaanae (Snyder, 1908) (Santa Ana sucker)
   |-- C. snyderi Gilbert, 1898 (Klamath largescale sucker)
   |-- C. tahoensis Gill & Jordan, 1878 (Tahoe sucker)
   |-- C. warnerensis Snyder, 1908 (Warner sucker)
   |-- C. wigginsi Herre & Brock, 1936 (Opata sucker)
   |-- (Catostomus) Eoc. R. As. Mioc.-Plioc. Pleist. R. NA.
   `-- (Pantosteus) Plioc. R. NA. 

Reference(s):