Anostomoides is a small genus of headstander characins in the family Anostomidae, the group whose members typically swim at a steep, nose-down angle while grazing over submerged wood and vegetation. The atlas covers 2 species, recorded from Brazil, Bolivia, Colombia, Guyana, Peru, and Venezuela - a broad Amazon-basin distribution. Atlas species run 12 in, on the larger side for a headstander, with the elongated body and small, downturned mouth typical of the family, adapted for picking at algae, detritus, and plant material from submerged surfaces.
The spotted headstander (A. atrianalis) is the better-known of the two in the hobby, occasionally available to specialist keepers of larger South American community tanks; its dark-spotted flanks and distinctive head-down posture make it a conversation piece rather than a mainstream aquarium fish. A. passionis is scarcely documented outside ichthyological literature. Conservation status is mixed - one atlas species is Least Concern, the other Data Deficient, reflecting how little targeted survey work has reached this genus.