A relict from the water: a new species from the río Magdalena basin (Colombia) of the mostly cis-Andean diversified genus Knodus (Characiformes: Stevardiidae)

A new stevardiid species from the río Magdalena basin (Colombia) is identified as belonging to the mostly cis-Andean genus Knodus, based on a comprehensive multilocus phylogenetic analysis of Stevardiidae. The new species represents the only known record of the genus from the Magdalena basin and is recovered as sister to a strictly Amazonian clade. The new species is diagnosed by a unique combination of meristic, morphometric, external, and osteological characters. Furthermore, a detailed osteological description of the new species is presented. Based on an assessment of the taxonomic distribution of putative synapomorphies of Knodus in Colombian species, Bryconamericus motatanensis is proposed to be reallocated to Knodus. The restricted distribution of the new species in a single tributary of the middle basin of the río Magdalena, suggests its relict presence in the Magdalena basin.