Some recent fish evolution papers that may be of interest:
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Axel Meyer, Siegfried Schloissnig, Paolo Franchini, Kang Du, Joost Woltering, Iker Irisarri, Wai Yee Wong, Sergej Nowoshilow, Susanne Kneitz, Akane Kawaguchi, Andrej Fabrizius, Peiwen Xiong, Corentin Dechaud, Herman Spaink, Jean-Nicolas Volff, Oleg Simakov, Thorsten Burmester, Elly M. Tanaka & Manfred Schartl (2021)
Giant lungfish genome elucidates the conquest of land by vertebrates.
Nature (advance online publication)
doi:
https://doi.org/10.1038/s41586-021-03198-8https://www.nature.com/articles/s41586-021-03198-8
Lungfishes belong to lobe-fined fish (Sarcopterygii) that in the Devonian 'conquered' land and gave rise to all land vertebrates, including humans. We determined the largest chromosome-quality animal genome, the Australian lungfish, Neoceratodus forsteri. Its vast size (~14x of human) is attributable mostly to huge intergenic regions and introns with high repeat content (â90%) whose components resemble tetrapods more (mostly LINE elements) than ray-finned fish. The lungfish genome continues to expand (its TEs are still active) independently and by different mechanisms than enormous salamander genomes. Synteny to other vertebrate chromosomes of 17 fully assembled macrochromosomes is maintained just as its conserved ancient homology of all microchromosomes to the ancestral vertebrate karyotype. Phylogenomic analyses ascertained that lungfish occupy an evolutionary key-position as closest living relatives to tetrapods, underscoring their importance for understanding innovations associated with terrestrialization. Preadaptations to living on land include gaining of limb-like _expression_ of developmental genes such as hoxc13 and sall1 in their lobed fins. Increased rates of evolution and duplication of genes associated with obligate air-breathing such as lung surfactants and the expansion of odorant receptor gene-families that detect airborne odours contribute to their tetrapod-like biology. These findings advance our understanding of this major transition during vertebrate evolution.
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Carlo Romano (2021)
A Hiatus Obscures the Early Evolution of Modern Lineages of Bony Fishes.
Frontiers in Earth Science 8:618853
doi:
https://doi.org/10.3389/feart.2020.618853https://www.frontiersin.org/articles/10.3389/feart.2020.618853/fullAbout half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic. They appear during a time when global fish faunas consisted of mostly cosmopolitan taxa, and contemporary bony fishes belonged mainly to non-neopterygian ("paleopterygian") lineages. In the Middle Triassic (Pelsonian substage and later), less than 10 myrs (million years) after the Permian-Triassic boundary mass extinction event (PTBME), neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. A major factor limiting our understanding of this "Triassic revolution" is an interval marked by a very poor fossil record, overlapping with the Spathian (late Olenekian, Early Triassic), Aegean (Early Anisian, Middle Triassic), and Bithynian (early Middle Anisian) substages. Here, I review the fossil record of Early and Middle Triassic marine bony fishes (Actinistia and Actinopterygii) at the substage-level in order to evaluate the impact of this hiatusânamed herein the SpathianâBithynian gap (SBG)--on our understanding of their diversification after the largest mass extinction event of the past. I propose three hypotheses: 1) the SSBE hypothesis, suggesting that most of the Middle Triassic diversity appeared in the aftermath of the Smithian-Spathian boundary extinction (SSBE; ~2 myrs after the PTBME), 2) the Pelsonian explosion hypothesis, which states that most of the Middle Triassic ichthyodiversity is the result of a radiation event in the Pelsonian, and 3) the gradual replacement hypothesis, i.e. that the faunal turnover during the SBG was steady and bony fishes were not affected by extinction events subsequent to the PTBME. Based on current knowledge, hypothesis three is favored herein, but further studies are necessary to test alternative hypotheses. In light of the SBG, claims of a protracted diversification of bony fishes after the PTBME should be treated with caution.
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https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.7168âPycnodontiformes was a successful lineage of primarily marine fishes that broadly diversified during the Mesozoic. They possessed a wide variety of body shapes and were adapted to a broad range of food sources. Two other neopterygian clades possessing similar ecological adaptations in both body morphology (âDapediiformes) and dentition (Ginglymodi) also occurred in Mesozoic seas. Although these groups occupied the same marine ecosystems, the role that competitive exclusion and niche partitioning played in their ability to survive alongside each other remains unknown. Using geometric morphometrics on both the lower jaw (as constraint for feeding adaptation) and body shape (as constraint for habitat adaptation), we show that while dapediiforms and ginglymodians occupy similar lower jaw morphospace, pycnodontiforms are completely separate. Separation also occurs between the clades in body shape so that competition reduction between pycnodontiforms and the other two clades would have resulted in niche partitioning. Competition within pycnodontiforms seemingly was reduced further by evolving different feeding strategies as shown by disparate jaw shapes that also indicate high levels of plasticity. Acanthomorpha was a teleostean clade that evolved later in the Mesozoic and which has been regarded as implicated in driving the pycnodontiforms to extinction. Although they share similar body shapes, no coeval acanthomorphs had similar jaw shapes or dentitions for dealing with hard prey like pycnodontiforms do and so their success being a factor in pycnodontiform extinction is unlikely. Sea surface temperature and eustatic variations also had no impact on pycnodontiform diversity patterns according to our results. Conversely, the occurrence and number of available reefs and hardgrounds as habitats through time seems to be the main factor in pycnodontiform success. Decline in such habitats during the Late Cretaceous and Palaeogene might have had deleterious consequences for pycnodontiform diversity. Acanthomorphs occupied the niches of pycnodontiforms during the terminal phase of their existence.
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