Priocharax nanus Toledo-Piza, Mattox & Britz 2014

Priocharax nanus can be distinguished from its congeners (P. ariel and P. pygmaeus) by having i,6 pelvic-fin rays (vs. i,5), a claustrum (vs. claustrum absent) and two postcleithra (vs. postcleithra absent). It can be further diagnosed from P. ariel by having 9-10 gill rakers on the lower limb of the first branchial arch (vs. 11-13), caudal peduncle length 13.5-16.8 % SL (vs. 18.1- 23.7 % SL); and 21-26 branched anal-fin rays (vs. 16-21) (Ref. 96862).Description: dorsal-fin rays ii.8-9; anal-fin rays iv-v, 21-26; pelvic-fin rays i,6. Pectoral fin withlarval structure; and pectoral-fin rays absent (Ref. 96862).

Dorsal soft rays (total): 1011; Vertebrae: 32 - 34

Collected in the black acidic waters of the Rio Negro basin around the submerged vegetation at depths of about 1 m or less and from an area exposed to the sun in warm, shallow water, approximately 50 cm deep (Ref. 96862).

Priocharax nanus is a minute species of fish native to the Rio Negro, Brazil. The species, which has a skeleton of cartilage, is almost completely transparent. It grows to a maximum length of 15.6 millimeters.