No abstract

Actinopterygians (ray-finned fishes) are the most diverse group of living fishes, but have a sparse Devonian fossil record restricted to low palaeolatitudes. Here we report a new actinopterygian from the Paraná Basin of Brazil, which occupied a circumpolar position in the Palaeozoic. Available geological evidence supports a Middle Devonian or older age for this taxon, which shares features of the mandibular symphysis with the latest Devonian Tegeolepis . A phylogenetic analysis resolves these two as sister taxa. This new record expands the palaeogeographic distribution of Devonian ray-fins and suggests that gaps in their fossil record might be filled by exploring poorly sampled high-latitude localities within the Malvinokaffric Realm.

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.

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...

-PALEOICHTHYOFAUNA OF THE PIMENTEIRA FORMATION (DEVONIAN), PARNAÍBA BASIN, PI, BRAZIL. The Pimenteira Formation extends through the east border of the Parnaíba Basin and corresponds to the Middle and Upper Devonian (Eifelian-Frasnian). This formation possesses as characteristic fauna an invertebrate association composed mostly of gastropods, brachiopods and trilobites. However, there are also rare vertebrate remains, normally isolated and poorly preserved. The vertebrate fauna have been studied since the middle of the twentieth century and until then, had not shown a considerable taxonomic variety, only comprising Ctenacanthus and Machaeracanthus spines. In this study, besides discussing the fossil fish material already known for this formation, we describe new fossil remains, including the description of: a new Machaeracanthus spine; the first spines of climatiiform acanthodians, one related to Ptomacanthus and the other to Climatius enodicosta; an Antarctilamna-like spine; and fragments of Ctenacanthus kegeli. Lastly, we present the possible first record of Placodermi for the Pimenteira Formation and the Parnaíba Basin. These occurrences expand considerably the vertebrate faunal composition of the Pimenteira Formation and helps to understand the connections among South American basins during the Devonian, due to the similarity between the Pimenteira Formation and other South American fossiliferous formations, especially those of Bolivia.