Hassar Eigenmann & Eigenmann, 1888: 158 [type species: Oxydoras orestis Steindachner 1875, by subsequent designation by Eigenmann 1910: 394]. Gender masculine. Originally proposed as a subgenus of Hemidoras.

Diagnosis. Hassar is diagnosed by a single exclusive character: basioccipital with a ventral ring-like arch surrounding aorta (Fig. 1); and by the combination of the following non-exclusive characters: 1) dark blotch in the middle to distal region of anterior branched rays of dorsal fin; 2) anteriormost postinfranuchal scutes reduced in size; 3) pores beneath the posterior cleithral process numerous; 4) maxillary barbels with 7 to 16 secondary barbels, and fleshy papillae restricted to anteriormost secondary barbels; 5) elongated mesethmoid, with lanceolate anterior tip and straight to slightly convex dorsal profile; 6) posterior cranial fontanel relatively large, extending posteriorly into the parietosupraoccipital; 7) first infraorbital long and slender, with dilated anterior extremity, articulating with the lateral border of mesethmoid; 8) ossified and extremely well-developed epioccipital process, sutured to the posterior nuchal plate; 9) less than 10 premaxillary teeth; 10) less than 20 dentary teeth; 11) well-developed nuchal foramina; 12) reduced anterior nuchal plate, enclosed by the posterior margin of the parietosupraoccipital and anterior margin of the middle nuchal plate; 13) 30 to 34 midlateral scutes on each side of body. See Discussion for additional notes on the aforementioned diagnostic features.

Etymology. Eigenmann & Eigenmann (1888) did not specify the origin of Hassar, but it possibly refers to the name commonly applied to certain catfishes in Guyana, such as Hoplosternum littorale or Hypostomus watawata (Eigenmann, 1912).