Abstract
A new characiform is herein described from the Eocene-Oligocene sediments exposed in the Aiuruoca basin, in southern Minas Gerais State, Brazil. Recently, two other characid species were described for this same fossil level: †Paleotetra aiuruoca and †Paleotetra entrecorregos. The holotype of this new characiform is represented by an articulated specimen preserved as part and counterpart, in which the most anterior part of the head is missing, including the jaws. Despite the lack of the diagnostic characters from the snout, a unique combination of characters allows its differentiation from other Neotropical characiforms, raising a new genus and species: †Bryconetes enigmaticus. Among these characters are: the presence of a supraorbital, dentary with inflated pentacuspidate teeth arranged in a single row, infraorbital 3 expanded and ornamented with punctuations and grooves, a large anal fin with iii+22-23 rays, and the caudal fin with 11 ventral procurrent rays of which the anteriormost are fused in laminar bones. A phylogenetic analysis using morphological data was performed and recovered †Bryconetes enigmaticus as a stem group to characiforms lacking a supraorbital. Based on the results of this analysis, a discussion of the potential relationships of the new taxon with other characiforms is presented.
Highlights
The order Characiformes is the largest Neotropical freshwater fish group and one of the most diverse groups of actinopterygians, with more than 2000 species (Eschmeyer & Fong, 2014)
Occurring in both sides of the Atlantic, the characiforms are much more diversified in the Neotropical region where 1830 species are registered, versus only 227 African species (Eschmeyer & Fong, 2014). Their modern distribution and fossils document the historical connection between Africa and South America, which when associated with their extreme diversity and restriction to freshwaters, makes characiforms an excellent group to investigate explanations for the composition and distribution of the modern Neotropical ichthyofauna
A characiform distinguished by the presence of a supraorbital not contacting the infraorbital 6, by the third infraorbital marked by diminutive punctuations and radial shallow grooves in its lateral surface, by the most anterior ventral procurrent caudal-fin rays fused in laminar medial bones, and by the possession of multicuspidate teeth, 36 vertebrae (17A + 19C), dorsal fin ii+9, anal fin long with iii+2223 rays
Summary
The order Characiformes is the largest Neotropical freshwater fish group and one of the most diverse groups of actinopterygians, with more than 2000 species (Eschmeyer & Fong, 2014). Most of the fish specimens are complete and articulated, including some bones and teeth, besides several impressions of young and very small undetermined individuals (Malabarba, 2004; Malabarba & Malabarba, 2008; Weiss et al, 2012) These facts associated to data from palynomorphs, plants, insects and vertebrates suggest that the Entre-Córregos Formation was deposited in a lake, relatively large and calm under reducing environmental conditions (Santos, 1999; Garcia et al, 2000; Bedani & Haddad, 2002; Delgado & Bernardes-de-Oliveira, 2004). Palynological data associated with foliar architectural features of the taphoflora point out a scenario of a very wet tropical forest under high temperatures (Garcia et al, 2000; CastroFernandes et al, 2013) during the deposition of this formation
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