A new stem fossil characid (Teleostei: Ostariophysi) from the Eocene-Oligocene of southeastern Brazil

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.Um novo caraciforme é descrito a partir de sedimentos do Eoceno -Oligoceno expostos na bacia de Aiuruoca , no sul de Minas Gerais, Brasil. Recentemente, outras duas espécies de Characidae foram descritas para este mesmo nível fossilífero: †Paleotetra aiuruoca e †Paleotetra entrecorregos. O holótipo do novo caraciforme é representado por um espécime articulado preservado como parte e contraparte, do qual falta a parte mais anterior da cabeça, incluindo mandíbula e maxila. Apesar da falta dos caracteres diagnósticos do focinho, uma combinação única de caracteres permite diferenciá-lo dos outros Characiformes neotropicais, levando a descrição de um gênero e espécie novos: †Bryconetes enigmaticus. Entre esses caracteres estão a presença de um supra-orbital, dentário com dentes pentacuspidados dispostos em uma única fileira, infraorbital 3 expandido e ornamentado com pontuações e sulcos, nadadeira anal com iii,22-23 raios e nadadeira caudal com 11 raios procurrentes ventrais sendo os mais anteriores fundidos em ossos laminares. A análise filogenética recuperou †Bryconetes enigmaticus como um "stem-grupo" de Characiformes sem supraorbital. Com base nestes resultados discutem-se as possíveis relações da nova espécie com outros Characiformes.

Vicariance and dispersal in southern hemisphere freshwater fish clades: a palaeontological perspective

“…Various tooth morphologies are present in these latest Cretaceous Bolivian deposits, indicating that the diversification of modern lineages (characids, serrasalmids and possibly acestrorhynchids) was underway by the end of the Late Cretaceous (Gayet et al ., , ). Complete fossils of South American characiforms (including bryconids, curimatids, triportheids and several characid lineages) are known from the Eocene–Oligocene Entre‐Corregos Formation and the Oligocene Tremembé Formation of southeastern Brazil (Malabarba, ; Weiss, Malabarba & Malabarba, ).…”

Paleogene emergence and evolutionary history of the Amazonian fossorial fish genus Tarumania (Teleostei: Tarumaniidae)

“…In fact, the Cretaceous-Paleogene El Molino Formation of Bolivia revealed the earliest fossils attributed to Characidae [Tetragonopterinae of Gayet et al (2001)]. Paleogene formations, in turn, revealed well-preserved and phenotypically intermediate characid genera such as †Paleotetra and †Bryconetes from the Eocene-Oligocene and †Megacheirodon from the Oligocene-Miocene (Travassos and Santos, 1955;Bührnheim et al, 2008;Malabarba and Malabarba, 2010;Weiss et al, 2012Weiss et al, , 2014. Fossils of Serrasalmidae begin to occur during the Late Cretaceous and early Paleogene (Gayet et al, 2001) and the evidence, in combination with molecular-dated phylogenies, suggests that the Paleogene was also the age for the early intrafamilial diversification (Kolmann et al, 2020;Melo et al, 2022).…”

Sperm phylogeny of Characidae (Teleostei, Characiformes)

“…The Characidae are a dominant Neotropical freshwater fish family that had an explosive radiation associated, among other features, to various reproductive strategies and morphologies associated to them (Quagio-Grassiotto et al, 2020). The huge number of species of this family, its rather recent radiation (Melo et al, 2022;Mirande, 2019;Weiss et al, 2012Weiss et al, , 2014, and a conservative morphological basis with parallely acquired features related to predation or miniaturization (Mirande, 2010), render difficult to get a stable phylogenetic hypothesis and morphological diagnoses. In this contribution we introduce a new, arguably independent, set of morphological characters that could be useful as a third way when general morphology and molecular data contradict to each other and to provide synapomorphies to diagnose clades.…”