A new species of Parotocinclus (Loricariidae: Hypoptopomatinae) from the rio Pardo basin, Bahia State, Brazil, with comments on the sexually dimorphic traits of the nares and olfactory lamellae.

A new species of Parotocinclus is described from lower rio Pardo basin, Bahia, Brazil. The new species differs from the majority of its congeners by the presence of a rudimentary or vestigial adipose fin, restricted to one to three small unpaired plates on the typical location of the fin. The new species differs from congeners that lack a well-developed adipose fin, and also from various other congeners, by a series of features including the absence of unicuspid accessory teeth and abdomen completely covered by plates similar in size. Additionally, mature males of the new species possess hypertrophied and a higher number of olfactory lamellae, when compared to similar-sized or even larger females. Hypertrophied and higher number of olfactory lamellae in males is shared with the congeners from the north-eastern Mata Atlântica freshwater ecoregion examined to the feature.