[3] Eurycheilichthys together with Pseudotocinclus, Microlepidogaster, Schizolecis, Otothyris and Pseudotothyris form a clade whose sister group is Epactionotus.

The head and body plates are covered with odontodes; these are larger on the ventral face of pelvic and pectoral fin spines.

[1][3] E. limulus shares with E. pantherinus a single synapomorphy: the derived presence of seven branched pectoral fin rays.

E. limulus is distinguished from E. pantherinus by a more narrow body, head and dorsal trunk with series of longitudinal light stripes (versus scattered dark blotches), and presence of an accessory ceratobranchial flange and filamentous gill rakers (versus absence of those features in E.

[1] The habitat at the type locality of E. limulus is a small river about 3–5 metres wide with moderate water current, bottom comprising some rocks but mostly sand and a large amount of marginal vegetation.