Mattox, de Souza, Toledo-Piza & Oliveira, 2021
A new species of miniature fish of the characid genus Priocharax is described from a small lake near the rio Ipixuna, rio Purus drainage, Amazonas State, Brazil. It is distinguished from all congeners except P. pygmaeus by the lower number of teeth on the maxilla and dentary. It differs from P. pygmaeus by the presence of two postcleithra and 22–27 branched anal-fin rays (vs absence and 19–22). The new species is further distinguished from other species of Priocharax by a combination of characters involving the number of pelvic-fin rays and branched anal-fin rays, the number of postcleithra, the shape of postcleithrum 3, and the absence of the claustrum. Molecular evidence based on COI sequences of all valid species of Priocharax also corroborates the validity of this new species.
Keywords: Biodiversity; Miniaturization; Ontogenetic truncation; Osteology; Taxonomy
Priocharax britzi, new species
Diagnosis: Priocharax britzi is distinguished from all congeners except P. pygmaeus by the lower number of teeth in the maxilla (21–30 vs 32–58) and dentary (26–29 vs 33–55). It differs from P. pygmaeus in the presence of two postcleithra (vs absence) and by having 22–27 (modes 25 and 26) branched anal-fin rays (vs 19–22, mode 19). The new species is further distinguished from P. nanus and P. varii by having i,5 pelvic-fin rays (vs i,6) and a slender and sinuous postcleithrum 3 (vs postcleithrum 3 relatively thick and straight), from P. ariel by the presence of 22–27 branched anal-fin rays (vs 16–22) and the presence of two postcleithra (vs absence). Priocharax britzi is further distinguished from P. varii by the absence of the adipose fin (vs presence) and from P. nanus by the absence of the claustrum (vs presence). Complementarily, Priocharax britzi has a shorter snout relative to the orbital diameter when compared to all congeners except P. nanus. This difference is reflected in the range of the proportion of snout length in relation to orbital diameter and its mean which is 45–59 (mean = 53.6; SD = 3.8) in P. britzi vs 60–76 (mean = 65.5; SD = 4.9) in P. pygmaeus, 54–81 (mean = 67.0; SD = 5.1) in P. varii and 54–84 (mean = 68.4; SD = 6.3) in P. ariel. The molecular analyses provide additional support towards the recognition of the new species.
Etymology. Priocharax britzi is named after Dr. Ralf Britz, noteworthy ichthyologist and a dear friend. Dr. Britz has mastered the world of small fishes and has described more than 20 miniature species, including two species of Priocharax. A noun in the genitive case.
|FIGURE 9: Small lake approximately 400 m from the rio Ipixuna, Canutama, Amazonas, Brazil, the type locality of Priocharax britzi.|
George Mendes Taliaferro Mattox, Camila da Silva de Souza, Mônica Toledo-Piza and Claudio Oliveira. 2021. A New Miniature Species of Priocharax (Characiformes: Characidae) from the upper rio Ipixuna, Purus Drainage, Brazil. Neotrop. ichthyol. 19(2); DOI: 10.1590/1982-0224-2021-0048