Utiaritichthysesguiceroi is described from the upper portion of the rio Juruena, rio Tapajós drainage, Mato Grosso State, Central Brazil. The new species distinguished from its two congeners, U. sennaebragai Miranda Ribeiro and U. longidorsalis Jégu, Tito de Morais & Santos, by having 99 to 101 perforated scales on lateral line (vs. 69 to 83), presence of 17 to19 prepelvic spines (vs. 9-13 in U. sennaebragai and 28-31 in U. longidorsalis), 20 to 21 postpelvic spines (vs. 15 to 19 in U. sennaebragai, and 14 in U. longidorsalis), and 23 to 25 circumpeduncular scales (vs. 30-48 in U. sennaebragai, and 33-35 in U. longidorsalis). Furthermore, the new species differs from U. longidorsalis by having larger interdorsal width, and adipose-fin base length (11.8-15.6 vs. 7.1-7.9% of SL, and 4.2-5.8 vs. 3.7-3.8% of SL, respectively).
Neotropical fish; Pacú borracha; Systematics; Taxonomy; Upper Juruena basin
