A new species of diminutive spiny driftwood catfish Spinipterus (Siluriformes: Auchenipteridae) from the Madeira River system, Amazon basin, Brazil

Abstract

Abstract The genus Spinipterus, a member of Auchenipterinae, was previously known from only two species: S. acsi, originally described from the Peruvian Amazon and later recorded from Juruá River in Brazil, and S. moijiri, described from the Purus River basin. In a 2020 expedition to the Madeira River basin during an intense drought that exposed lateritic rocks in the Guaporé River bed revealed a diminutive, previously undescribed species of Spinipterus. The new species differs from its congeners, S. acsi and S. moijiri, by the marbled body coloration, lower number of soft pectoral-fin rays, a longer head, a smaller interorbital distance, reduced maxillary barbels, and other osteological features. This new species, described herein, underscores the underestimated diversity within Spinipterus, likely due to its habitat specificity and rarity in ichthyological collections, highlighting the importance of exploring unusual microhabitats in revealing hidden components of Neotropical fish diversity. A key to identification of the species of Spinipterus is provided.