Key to the Species of Semotilus

1a. Dorsal fin origin on or only slightly behind vertical from origin of pelvic fin; lateral stripe narrow, narrower above pelvic fins than eye diameter; cuadal spot quadrate.
creek chub

Semotilus atromaculatus

1b. Dorsal fin origin well behind vertical from origin of pelvic fin; lateral stripe broad, deeper above pelvic fins than eye diameter; caudal spot triangular.
dixie chub

Semotilus thoreauianus