Cranial anatomy of the predatory actinopterygianBrazilichthys macrognathusfrom the Permian (Cisuralian) Pedra de Fogo Formation, Parnaíba Basin, Brazil

Abstract

Brazilichthys macrognathus is the only named actinopterygian from the Permain (Cisuralian) Pedra de Fogo Formation of northeastern Brazil, where it is represented by a single three-dimensionally preserved but incompletely described skull of unclear systematic placement. We used X-ray computed microtomography (µ-CT) to better document its anatomy and phylogenetic affinities. µ-CT reveals parts of the internal skeleton. We correct errors in original description, including the number of infraorbital bones and the misidentification of the dermosphenotic as sclerotic ossifications. These reinterpretations of external anatomy are joined by new data on internal structure, including the palate, parasphenoid, and branchial and hyoid arches. A maximum parsimony analysis of anatomical data resolves Brazilichthys as a stem actinopterygian, crownward of all Devonian species. This placement is supported by the absence of a dermosphenotic posterior ramus and the presence of opercular process of the hyomandibula. A similar placement is suggested by a Bayesian analysis of this same dataset, although relationships throughout the tree are less resolved. Our results reject previous interpretations of Brazilichthys as a relative of Birgeriidae, a Triassic group consistently placed within the actinopterygian crown. Although Acrolepis is too poorly known to be included in our analysis, we also reject a close relationship between this taxon and Brazilichthys, as their only shared similarities appear to be broadly distributed among early actinopterygians. 1969) or detailed descriptions of only single constituent taxa (e.g. Ebenaqua from Rangal Coal Measures of Blackwater, Australia; Campbell and Phuoc, 1983). Brazilian deposits yield the vast majority of Permo-Carboniferous actinopterygians known from South America (Cione et al., 2010), with only a handful of examples known from elsewhere, mostly based on poorly preserved specimens (e.g. Beltan, 1978; this material is now considered lost, pers. comm. Piñeiro, G., April 18, 2017). Despite the relative neglect of the South American record of Paleozoic fishes, sporadic research efforts reveal substantial assortment of Permian actinopterygians from Brazil. These span the Permian and overwhelmingly derive from deposits in the Paraná Basin of southern Brazil: the Rio do Sul (Cisuralian in age and yielding Elonichthys gondwanus; Richter et al., 1985), Campo Mourão (Cisuralian in age and yielding Roslerichthys riomafrensis and Santosichthys mafrensis; Hamel, 2005; Malabarba, 1988), Rio Bonito Formation (Guadalupian-Lopingian in age yielding Tholonosteon santacatarinae; Richter et al., 1985) Rio do Rasto (Guadalupian-Lopingian in age and yielding Rubidus pascoalensis and Paranaichthys longianalis; Richter, 2002; Dias, 2012), and Corumbataí (Lopingian in age and yeilding Tholonotus brasiliensis and Angatubichthys mendesi; Dunkle and Schaeffer, 1956;Figueiredo and Carvalho, 2004) formations. By contrast, Brazilichthys macrognathus is the only Permian actinopterygian known from the Parnaíba Basin in...

The early diversification of ray‐finned fishes (Actinopterygii): hypotheses, challenges and future prospects

“…(2009); (C) Figueroa et al . (2019); and (D) Elliott (2016). The actinopterygian crown node is indicated in analyses that include extant taxa.…”

“…Dietze, 2000; Elliott, 2016) with broader analyses that attempt to span the actinopterygian radiation (e.g. Giles et al ., 2017; Figueroa et al ., 2019, 2021; Ren & Xu, 2021) is sorely needed. Among the most recent iterations of the Giles et al .…”

“…Although most analyses draw on multiple sources, two main subsequent 'lineages' of analyses have arisen, both with a focus shifted towards relationships of actinopterygians rather than early bony fishes. , which attempted a major synthesis of existing character matrices, sourcing characters from previous cladistic and phylogenetic studies, heavily influenced and Swartz (2009), while Friedman & Blom (2006) became the basis of Choo (2012) and all subsequent analyses derived from that matrix (Giles et al, 2015(Giles et al, , 2017Argyriou et al, 2018;Choo et al, 2019;Figueroa et al, 2019Figueroa et al, , 2021Fig. 9).…”

“…Dietze, 2000;Elliott, 2016) with broader analyses that attempt to span the actinopterygian radiation (e.g. Giles et al, 2017;Figueroa et al, 2019Figueroa et al, , 2021Ren & Xu, 2021) is sorely needed. Among the most recent iterations of the Giles et al (2017) matrix are studies beginning to expand the geographic spread of taxa by including actinopterygians from South America (Figueroa et al, 2019(Figueroa et al, , 2021.…”

Exceptional fossil preservation and evolution of the ray-finned fish brain

“…However, both groups show extreme morphological specialisations resulting from their long independent evolutionary histories. As a stem actinopterygian separated from the common ancestor of all living species by tens—rather than hundreds—of millions of years 3,29,52,53 , † Coccocephalichthys provides unique information bearing on primitive brain anatomy in ray-finned fishes and sequences of change within the group. Most notably, the brain of † Coccocephalichthys allows us to clarify neurological synapomorphies of the ray-finned fish total group (i.e.…”