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Dario Faustino-Fuster (3)

Description: Phenacorhamdia suia differs from all congeners by having an atypical mottled coloured body (vs. uniformly counter-shaded, without mottled pattern; with a longitudinal dark brown stripe along the dorsal half of the body in P. unifasciata), and by having all fins with interradial membranes pigmented and mottled (vs. fins with interradial membranes hyaline). Additionally, P. suia differs from all congeners, except P. taphorni by having multicuspid teeth (vs. conical teeth). The new species differs from some of its congeners by maxillary barbel reaching pectoral-fin origin (vs. maxillary barbel reaching the end of adpressed pectoral fin in P. anisura, P. boliviana, P. nigrolineata, and P. tenebrosa; reaching half the length of pectoral fin in P. tenuis; surpassing pectoral fin in P. provenzanoi and P. taphorni; reaching pelvic-fin origin in P. macarenensis); lacking a short extension of the first pectoral-fin ray (vs. present in P. anisura, P. macarenensis, P. nigrolineata, P. provenzanoi, and P. taphorni), by caudal fin deeply forked with extremely elogated and pointed lobes (vs. moderately pointed in P. hoehnei; rounded in P. somnians); and by having 43-45 total vertebrae (vs. 39 in P. taphorni; 41 in P. hoehnei; 41-42 in P. tenebrosa; 46-47 P. unifasciata; 47-48 in P. provenzanoi; 53-55 in P. tenuis). Habitat: Phenacorhamdia suia is known from nine localities from the upper and lower Xingu River basins. The type-locality is Santa Luzia stream, Comandante Fontoura River basin. Other sites are Culuene, Coronel Vanick, Suiazinho, Turvo Rivers, Capim and Fonte Boa streams, and two unnamed streams. Colouration: Overall pigmentation mottled (with light brown background and irregular dark brown blotches formed by minutes and concentrated melanophores that overlap each other), becoming ventrally mostly unpigmented. Interradial membranes of all fins pigmented as the body. Etymology: The specific name “suia” refers to the Suias indigenous people who, since the 90’s, have stood out in the fight to protect the Suiá-Missu River environment and for recovery of their traditional lands outside the limits of Xingu park. A noun in apposition. Holotype: 81.8 mm SL.

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Heptapteridae

South America: Upper and lower Xingu River basins, Brazil. Type locality: Santa Luzia stream, Comandante Fontoura River basin.

0.8cm. (¾ins)

24-26°C (75-79°F)

6.0-7.0.

Silva, Gabriel S. C., Ochoa, Luz E. and Castro, Íthalo S. New species of Phenacorhamdia (Siluriformes: Heptapteridae) from the Xingu River basin. Neotropical Ichthyology [online]. 2022.