This species is distinguished from other Astyanax species in central-northern Mexico by the following characters: A 19-23, mode 20 (21-25, mode 23, in A. mexicanus, 18-20, mode 18, in A. rioverde); modally 7 scale-rows between lateral line and dorsal-fin origin (modally 8 in A. mexicanus, A. acatlanensis); nuptial spines or tubercles, just on anal-fin rays, all simple (just on pelvic fins in A. rioverde, and at least some bifid in A. mexicanus, A. acatlanensis); body more slender than A. mexicanus, A. rioverde, mean 34% SL (vs mean 37% SL); anterior fontanel, sharp-tipped (blunt in A. mexicanus); infraorbital IV, rectangular, with no projections (square, with projections in A. acatlanensis, A. mexicanus, A. tehuacanensis); ventral side of ceratohyal, straight (vs undulate). Posterior edge of interopercle, without a spine (with a spine in A. mexicanus, A. tehuacanensis); postcleithrum caudad process concave-sided (straight in A. mexicanus); largest hypuric plate, rostral border straight (concave in A. mexicanus) (Ref. 118583).