Sternarchogiton zuanoni de Santana & Vari 2010

Sternarchogiton zuanoni is diagnosed from S. labiatus in the number of total anal-fin rays (129–153 versus 156–168, respectively), the interorbital width (28.8–39.4% of HL versus 19.5–24.6%, respectively), the body depth (13.3–17.3% of LEA versus 10.3–12.0%, respectively), the coloration of the anal fin (completely hyaline versus the presence of scattered brown speckling and a dark distal margin, respectively), the form of the lower lip (unelaborated versus the presence of a prominent tri-lobed structure, respectively), and the number of rows of conical teeth on the dentary (one versus two rows, respectively). Sternarchogiton zuanoni is distinguished from S. nattereri in the number of total anal-fin rays (129–153 versus 180–198, respectively), the interorbital width (28.8–39.4% of HL versus 19.9–27.6%, respectively), the length of the caudal appendage (22.4– 30.7% of LEA versus 14.6–20.4%, respectively), and the premaxillary dentition (teeth absent versus present in some sexually dimorphic males, respectively). Sternarchogiton zuanoni is diagnosable from S. porcinum in the number of total anal-fin rays (129–153 versus 182–216, respectively), the interorbital width (28.8–39.4% of HL versus 18.8–23.9%, respectively), the head width (46.2–57.3% of HL versus 39.1– 44.6%, respectively), the orbital diameter (9.3–14.1% of HL versus 4.5–7.7%, respectively), the coloration of the pectoral and anal fins (completely hyaline versus with black margins, respectively), and the dorsal profile of the head (distinctly convex versus straight or slightly convex, respectively). Sternarchogiton zuanoni is distinguished from S. preto in the number of total anal-fin rays (129–153 versus 189– 210, respectively), the interorbital width (28.8–39.4% of HL versus 17.8–25.9%, respectively), the orbital diameter (9.3– 14.1% of HL versus 2.9–8.3%, respectively), the coloration of the pectoral and anal fins (completely hyaline versus with black margins, respectively), and the premaxillary dentition (teeth absent versus present, respectively) (Ref. 83662).

Available specimens of Sternarchogiton zuanoniwere captured in Cachoeira de Kaituká at locations in rapids and in pools at the base of waterfalls. Sternarchogiton zuanoni is the sole species known to be associated with rapidlyflowing rivers with rocky beds, whereas the examined samples of other congeners originate from main channels of deep-water rivers, often in benthic settings (de Santana and Crampton, 2007). Three other species of the Apteronotidae, Megadontognathus kaitukaensis (Campos-da-Paz, 1999) and two undescribed species of Sternarchorhynchus (de Santana and Vari, in press), were also captured within Cachoeira de Kaituká (Ref. 83662).