A redescription of deep-channel ghost knifefish, Sternarchogiton preto (Gymnotiformes: Apteronotidae), with assignment to a new genus

Abstract

From a study of morphological and molecular datasets we determine that a species originally described as Sternarchogiton preto does not form a monophyletic group with the other valid species of Sternarchogiton including the type species, S. nattereri. Previously-published phylogenetic analyses indicate that this species is sister to a diverse clade comprised of six described apteronotid genera. We therefore place it into a new genus diagnosed by the presence of three cranial fontanels, first and second infraorbital bones independent (not fused), the absence of an ascending process on the endopterygoid, and dark brown to black pigments over the body surface and fins membranes. We additionally provide a redescription of this enigmatic species with an emphasis on its osteology, and provide the first documentation of secondary sexual dimorphism in this species.

Sexual Dimorphism in the Electric Knifefish Sternarchogiton labiatus (Gymnotiformes: Apteronotidae) with a Hypermorphic Snout and Oral Jaws

“…The sexual dimorphism in Sternarchogiton labiatus and S. nattereri appears to be similar to that described by Bernt et al (2020: figs. 11, 13) in Tenebrosternarchus preto , a species initially assigned to the genus Sternarchogiton .…”

“…Sternarchogiton labiatus was described by de Santana and Crampton (2007) in a revision of the genus along with S. preto , which was subsequently transferred to a new genus, Tenebrosternarchus (Bernt et al, 2020). This transfer left three valid species of Sternarchogiton : S. labiatus , S. nattereri , and S. porcinum .…”

A new species of sexually dimorphic and rheophilic ghost knifefish (Apteronotidae: Gymnotiformes) from the Amazon basin

“…Meristic data for species in Apteronotus and other Gymnotiformes genera were taken by direct examination and/or from the literature (Albert, 2001;Bernt & Albert, 2017;Bernt et al, 2018Bernt et al, , 2020Campos-da-Paz, 1995, 1999Evans et al, 2017a;Fernández-Yépez, 1968;Hulen et al, 2005;Hilton et al, 2007;Hilton & Cox Fernandes, 2017;Lundberg et al, 2013;Mago-Leccia, 1994;Maldonado-Ocampo et al, 2011;de Santana, 2002de Santana, , 2003, 2005de Santana & Cox Fernandes, 2012;de Santana & Lehmann, 2006;de Santana & Crampton, 2007, 2010, 2011de Santana & Vari, 2009, 2010Schultz, 1949;Steindachner, 1881;Triques, 2011;.…”