Petulanos is a genus of headstanders (family Anostomidae) from the Guiana Shield of northern South America, with the three atlas species - P. intermedius, the plicatus headstander (P. plicatus), and the toothed headstander (P. spiloclistron) - recorded from Guyana and Suriname. Anostomids are characiforms named for their distinctive head-down, oblique swimming posture, used to graze algae, biofilm, and small invertebrates from submerged wood and leaf litter in the clearwater and blackwater rivers of the region. Atlas species run 3.5–8 in, and the toothed headstander's common name points to the genus's diagnostic dentition, one of the traits used to separate it from the larger, more familiar genus Leporinus.
Headstanders in general are a long-established part of the community-cichlid aquarium hobby, kept for their unusual feeding posture and their appetite for algae on driftwood and hardscape, though Petulanos species specifically are seen far less often in the trade than their Leporinus and Anostomus relatives and should be expected mainly through specialist South American fish importers rather than general retail. Two of the three atlas species are assessed as Least Concern; the third - data sparse beyond that - carries an IUCN status of Endangered, a reminder that even Guiana Shield rivers with relatively low human pressure can host range-restricted fish of conservation concern.