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Gill-skeleton modifications for processing prey represent a major source of functional innovation in living ray-finned fishes. Here we present the oldest actinopterygian tongue bite, derived from the gill skeleton, in the Middle Pennsylvanian (approx. 310 Ma) †Platysomus parvulus. Unrelated to extant tongue biters, this deep-bodied taxon possesses a large, multipartite basibranchial tooth plate opposing an upper tooth field centred on the vomer. This branchial structure occurs in conjunction with toothed jaws, indicating a role for both the basibranchial plate and jaws in feeding. †P. parvulusillustrates the assembly of the tongue bite in the geologically younger †Bobasatraniidae: large opposing dorsal (vomerine) and ventral (basibranchial) crushing plates associated with toothless jaws. The origin of tongue bites falls within the Carboniferous actinopterygian radiation, although it postdates the first signs of the consumption of hard prey (durophagy) in other ray-finned lineages by several million years. This lends support to a protracted model of actinopterygian diversification in the aftermath of the end-Devonian extinction. 

The separation of closely related terrestrial or freshwater species by vast marine barriers represents a biogeographical riddle. Such cases can provide evidence for vicariance, a process whereby ancient geological events like continental rifting divided ancestral geographical ranges. With an evolutionary history extending tens of millions of years, freshwater ecology, and distribution encompassing widely separated southern landmasses, osteoglossid bonytongue fishes are a textbook case of vicariance attributed to Mesozoic fragmentation of the Gondwanan supercontinent. Largely overlooked fossils complicate the clean narrative invoked for extant species by recording occurrences on additional continents and in marine settings. Here, we present a new total-evidence phylogenetic hypothesis for bonytongue fishes combined with quantitative models of range evolution and show that the last common ancestor of extant osteoglossids was likely marine, and that the group colonized freshwater settings at least four times when both extant and extinct lineages are considered. The correspondence between extant osteoglossid relationships and patterns of continental fragmentation therefore represents a striking example of biogeographical pseudocongruence. Contrary to arguments against vicariance hypotheses that rely only on temporal or phylogenetic evidence, these results provide direct palaeontological support for enhanced dispersal ability early in the history of a group with widely separated distributions in the modern day. 

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A complex brain is central to the success of backboned animals. However, direct evidence bearing on vertebrate brain evolution comes almost exclusively from extant species, leaving substantial knowledge gaps. Although rare, soft-tissue preservation in fossils can yield unique insights on patterns of neuroanatomical evolution. Paleontological evidence from an exceptionally preserved Pennsylvanian (ca. 318 Ma) actinopterygian, Coccocephalus, calls into question prior interpretations of ancestral actinopterygian brain conditions. However, ordering and timing of major evolutionary innovations such as an everted telencephalon, modified meningeal tissues, and hypothalamic inferior lobes remain unclear. Here we report two distinct actinopterygian morphotypes from the latest Carboniferous-earliest Permian (~299 Ma) of Brazil that show extensive soft-tissue preservation of brains, cranial nerves, eyes and potential cardiovascular tissues. These fossils corroborate inferences drawn from Coccocephalus, while adding new information about neuroanatomical evolution. Skeletal features indicate that one of these Brazilian morphotypes is more closely related to living actinopterygians than the other, which is also reflected in soft-tissue features. Significantly, the more crownward morphotype shows a key neuroanatomical feature of extant actinopterygians–an everted telencephalon–that is absent in the other morphotype and Coccocephalus. All preserved Paleozoic actinopterygian brains show broad similarities including an invaginated cerebellum, hypothalamus inferior lobes, and a small forebrain. In each case, preserved brains are substantially smaller than the enclosing cranial chamber. The neuroanatomical similarities shared by this grade of Permo-Carboniferous actinopterygians reflect probable primitive conditions for actinopterygians, providing a revised model for interpreting brain evolution in a major branch of the vertebrate tree of life. 

Abstract Osteoglossid bonytongues (arapaimas, arowanas, and relatives) are extant tropical freshwater fishes with a relatively abundant and diverse fossil record. Most osteoglossid fossils come from a 25-million-year interval in the early Palaeogene, when these fishes were distributed worldwide in both freshwater and marine environments. Despite their biogeographic and palaeoecological relevance, and a relative abundance of well-preserved material, the evolutionary relationships between these Palaeogene forms and extant bonytongues remain unclear. Here we describe a new genus of bonytongue from early Eocene marine deposits of Morocco, represented by an articulated, three-dimensionally preserved skull with associated pectoral girdle. This taxon is characterized by an elongated snout, contrasting with the short jaws usually found in marine representatives of the clade. A revision of morphological characters in bonytongues allows us to place this new genus, together with other marine and freshwater Eocene taxa, within crown osteoglossids and closely related to extant arapaimines. The discovery of the new Moroccan taxon hints at a previously underestimated eco-morphological diversity of marine bonytongues, highlighting the diverse trophic niches that these fishes occupied in early Palaeogene seas. 

Abstract Evolutionary innovations have played an important role in shaping the diversity of life on Earth. However, how these innovations arise and their downstream effects on patterns of morphological diversification remain poorly understood. Here, we examine the impact of evolutionary innovation on trait diversification in tetraodontiform fishes (pufferfishes, boxfishes, ocean sunfishes, and allies). This order provides an ideal model system for studying morphological diversification owing to their range of habitats and divergent morphologies, including the fusion of the teeth into a beak in several families. Using three-dimensional geometric morphometric data for 176 extant and fossil species, we examine the effect of skull integration and novel habitat association on the evolution of innovation. Strong integration may be a requirement for rapid trait evolution and facilitating the evolution of innovative structures, like the tetraodontiform beak. Our results show that the beak arose in the presence of highly conserved patterns of integration across the skull, suggesting that integration did not limit the range of available phenotypes to tetraodontiforms. Furthermore, we find that beaks have allowed tetraodontiforms to diversify into novel ecological niches, irrespective of habitat. Our results suggest that general rules pertaining to evolutionary innovation may be more nuanced than previously thought. 

Complex patterns of genome evolution associated with the end-Cretaceous [Cretaceous-Paleogene (K–Pg)] mass extinction limit our understanding of the early evolutionary history of modern birds. Here, we analyzed patterns of avian molecular evolution and identified distinct macroevolutionary regimes across exons, introns, untranslated regions, and mitochondrial genomes. Bird clades originating near the K–Pg boundary exhibited numerous shifts in the mode of molecular evolution, suggesting a burst of genomic heterogeneity at this point in Earth’s history. These inferred shifts in substitution patterns were closely related to evolutionary shifts in developmental mode, adult body mass, and patterns of metabolic scaling. Our results suggest that the end-Cretaceous mass extinction triggered integrated patterns of evolution across avian genomes, physiology, and life history near the dawn of the modern bird radiation. 

Abstract Actinopterygii is a major extant vertebrate group, but limited data are available for its earliest members. Here we investigate the morphology of Devonian actinopterygians, focusing on the lower jaw. We use X‐ray computed tomography (XCT) to provide comprehensive descriptions of the mandibles of 19 species, which span the whole of the Devonian and represent roughly two‐thirds of all taxa known from more than isolated or fragmentary material. Our findings corroborate previous reports in part but reveal considerable new anatomical data and represent the first detailed description for roughly half of these taxa. The mandibles display substantial variation in size, spanning more than an order of magnitude. Although most conform to a generalized pattern of a large dentary and one or two smaller infradentaries, XCT data reveal significant differences in the structure of the jaw and arrangement of teeth that may be of functional relevance. We report the presence of a rudimentary coronoid process in several taxa, contributed to by the dentary and/or infradentaries, as well a raised articular region, resulting in a mandible with an offset bite and that functions as a bent level arm. Among the most striking variation is that of tooth morphology: several taxa have heterodont dentary teeth that vary in size and orientation, and multiple variations on enlarged, whorl‐like and posteriorly‐oriented anterior coronoid dentition are observed. We use these new data to revise morphological characters that may be of phylogenetic significance and consider the possible functional implicationds of these traits. The observed variation in mandible form and structure suggests previously unappreciated functional diversity among otherwise morphologically homogenous Devonian ray‐finned fishes.