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Representatives of the six gymnotiform families Apteronotidae (A), Sternopygidae (S), Gymnotidae (G), Electrophoridae (E), Hypopomidae (H), and Rhamphichthyidae (R). Top to bottom, and left to right, are: Rhamphichthys rostratus (R), Archolaemus janeae (S), Sternarchorhamphus muelleri (A), Eigenmannia magoi (S), Gymnotus carapo (G), Sternarchorhynchus sp. (A), Apteronotus galvisi (A), Orthosternarchus tamandua (A), “Apteronotus” (Genus B) cuchillejo (A), Apteronotus eschmeyeri (A), Apteronotus cf. albifrons (A), Gymnorhamphichthys sp. (R), Sternarchorhynchus marreroi (A), Sternopygus aequilabiatus (S), Adontosternarchus devenanzii (A), Steatogenys duidae (R), Brachyhypopomus occidentalis (H), Hypopomus artedi (H), and Electrophorus multivalvulus (E). in Janzen, Sabaj, Crampton et Lovejoy, 2026. Photos by M. Sabaj. |
Highlights:
• New 9 gene molecular tree for 202 species of Neotropical electric knifefishes (order Gymnotiformes)
• A new taxonomy is proposed, based on the most extensive phylogenetic analysis to date.
• Strong phylogenetic support for 6 families, including the Electrophoridae (electric eels)
• Two main groups of species defined by either pulse or wave-type electric signals.
• Two new suborders: Pulseoidei for pulse-type species and Sinusoidei for wave-type species.
Abstract
The order Gymnotiformes—Neotropical electric eels and knifefishes—comprise a distinctive lineage of freshwater fishes characterized by electrogenesis and electroreception. Despite their ecological, evolutionary, and neurobiological significance, phylogenetic relationships within the order remain incompletely resolved. We present the most taxonomically inclusive molecular phylogeny of Gymnotiformes to date, based on two mitochondrial and seven nuclear genes from 202 species representing 31 of 36 extant genera. Maximum likelihood and Bayesian inference analyses provide strong support for a concordant species-level phylogenetic arrangement that we use to propose a revised classification of Gymnotiformes, including new suprageneric names and reassignments of some taxa and species. We found support for six monophyletic families, including Electrophoridae (electric eels). We propose two new suborders corresponding to electric signal type: Pulseoidei (pulse-type) and Sinusoidei (wave-type), an arrangement that does not allow determination of whether a pulse or wave-type signal was ancestral. In Apteronotidae, the subfamilies Sternarchorhamphinae and Apteronotinae are supported; within Apteronotinae, we establish the tribe Steatogenini to include Porotergus, Sternarchella, and close relatives. We resolve the non-monophyly of Apteronotus with generic reassignments. For Sternopygidae, we support the monophyletic subfamilies Sternopyginae and Eigenmanniinae and resolve polyphyly in Rhabdolichops and Eigenmannia via generic reassignments. Within Gymnotus, we support six species groups. We confirm the sister-group relationship between Hypopomidae and Rhamphichthyidae and clarify their internal structure, including support for six species groups within the diverse genus Brachyhypopomus. Our study provides a robust phylogenetic framework for Gymnotiformes and establishes a foundation for future work on systematics, biogeography, trait evolution, and comparative neurobiology.
Keywords: Neotropical, Systematics, Electric eel, Knifefish, Electric organ discharges
Sinusoidei subord. nov. changed from “Sinusoidea” of Albert 2001
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Representatives of the six gymnotiform families Apteronotidae (A), Sternopygidae (S), Gymnotidae (G), Electrophoridae (E), Hypopomidae (H), and Rhamphichthyidae (R). Top to bottom, and left to right, are: Rhamphichthys rostratus (R), Archolaemus janeae (S), Sternarchorhamphus muelleri (A), Eigenmannia magoi (S), Gymnotus carapo (G), Sternarchorhynchus sp. (A), Apteronotus galvisi (A), Orthosternarchus tamandua (A), “Apteronotus” (Genus B) cuchillejo (A), Apteronotus eschmeyeri (A), Apteronotus cf. albifrons (A), Gymnorhamphichthys sp. (R), Sternarchorhynchus marreroi (A), Sternopygus aequilabiatus (S), Adontosternarchus devenanzii (A), Steatogenys duidae (R), Brachyhypopomus occidentalis (H), Hypopomus artedi (H), and Electrophorus multivalvulus (E). Photos by M. Sabaj. |
Francesco H. Janzen, Mark H. Sabaj, William G.R. Crampton, Nathan R. Lovejoy, 2026. Molecular Phylogenetics and A New Taxonomy of the Neotropical Electric Fishes (Actinopterygii: Otophysi: Gymnotiformes). Molecular Phylogenetics and Evolution. In Press, 108678. DOI: doi.org/10.1016/j.ympev.2026.108678 [10 July 2026]