Hemibrycon
sanjuanensis, new species, is described from the upper San Juan River drainage, Pacific versant, Colombia. It is distinguished from Hemibrycon
boquiae, Hemibrycon
brevispini, Hemibrycon
cairoense, Hemibrycon
colombianus, Hemibrycon
mikrostiktos, Hemibrycon
metae, Hemibrycon
palomae, Hemibrycon
rafaelense and Hemibrycon
tridens by the presence of a circular or oblong humeral spot that is located two scales posterior to the opercle (vs. 3–4 scales in Hemibrycon
palomae, Hemibrycon
rafaelense, Hemibrycon
brevispini and Hemibrycon
cairoense, and 0–1 scales, in Hemibrycon
metae and Hemibrycon
boquiae). It further differs from Hemibrycon
colombianus in having a round or oblong humeral spot (vs. rectangular). It differs from Hemibrycon
beni, Hemibrycon
dariensis, Hemibrycon
divisorensis, Hemibrycon
helleri, Hemibrycon
huambonicus, Hemibrycon
inambari, Hemibrycon
jabonero, Hemibrycon
jelskii, Hemibrycon
mikrostiktos, Hemibrycon
polyodon, Hemibrycon
quindos, Hemibrycon
raqueliae, Hemibrycon
santamartae, Hemibrycon
surinamensis, Hemibrycon
taeniurus, Hemibrycon
tridens, and Hemibrycon
yacopiae in having melanophores on the posterior margins of the scales along the sides of body (vs. lacking melanophores on margins of scales along entire length of the sides of body). The new species differs from all congeners mentioned above in having, among other features, six teeth in the outer premaxillary row arranged in a straight line (vs. five or fewer teeth not arranged in straight line except Hemibrycon
cairoense with two to six teeth in the outer premaxillary row).