This short page covers the stem group of the actinopteran fishes (clade Actinopteri, superclass Actinopterygii). This clade contains an enormous number of species in more than 5,000 genera and more than 500 families (Encyclopedia of Life, eol.org/pages/46561162).
The actinopteran clade is based primarily on molecular phylogenetic analysis (Near et al, 2012). Few morphological studies provide support for the clade (Betancur-R et al, 2017), and there are no fossil species for which there is consensus in the literature for their assignment to the stem-Actinopteri. Two candidates have been proposed: Birgeria groenlandica (Giles et al, 2017) and Pteronisculus sp. (Xu et al, 2018), but other studies places these in the stem-Actinopterygii (Argyriou et al (2018) for Birgeria and Ren and Xu (2021) for Pteronisculus) or possibly, in the case of Birgeria, in the stem-Chondrostei (Figueroa et al, 2019).
In view of these uncertainties, we will not attempt to say more about the stem-to-crown transition of the Actinopteri.
The actinopteran clade is based primarily on molecular phylogenetic analysis (Near et al, 2012). Few morphological studies provide support for the clade (Betancur-R et al, 2017), and there are no fossil species for which there is consensus in the literature for their assignment to the stem-Actinopteri. Two candidates have been proposed: Birgeria groenlandica (Giles et al, 2017) and Pteronisculus sp. (Xu et al, 2018), but other studies places these in the stem-Actinopterygii (Argyriou et al (2018) for Birgeria and Ren and Xu (2021) for Pteronisculus) or possibly, in the case of Birgeria, in the stem-Chondrostei (Figueroa et al, 2019).
In view of these uncertainties, we will not attempt to say more about the stem-to-crown transition of the Actinopteri.
References
Argyriou, T., Giles, S., Friedman, M., Romano, C., Kogan, I., & Sánchez-Villagra, M. R. (2018). Internal cranial anatomy of Early Triassic species of †Saurichthys (Actinopterygii: †Saurichthyiformes): implications for the phylogenetic placement of† saurichthyiforms. BMC evolutionary biology, 18(1), 161.
Betancur-R, R., Wiley, E. O., Arratia, G., Acero, A., Bailly, N., Miya, M., ... & Orti, G. (2017). Phylogenetic classification of bony fishes. BMC evolutionary biology, 17(1), 1-40.
Figueroa, R. T., Friedman, M., & Gallo, V. (2019). Cranial anatomy of the predatory actinopterygian Brazilichthys macrognathus from the Permian (Cisuralian) Pedra de Fogo Formation, Parnaíba Basin, Brazil. Journal of Vertebrate Paleontology, 39(3), e1639722.
Giles, S., Xu, G. H., Near, T. J., & Friedman, M. (2017). Early members of ‘living fossil’lineage imply later origin of modern ray-finned fishes. Nature, 549(7671), 265.
Near, T. J., Eytan, R. I., Dornburg, A., Kuhn, K. L., Moore, J. A., Davis, M. P., ... & Smith, W. L. (2012). Resolution of ray-finned fish phylogeny and timing of diversification. Proceedings of the National Academy of Sciences, 109(34), 13698-13703.
Ren, Y., & Xu, G. H. (2021). A new species of Pteronisculus from the Middle Triassic (Anisian) of Luoping, Yunnan, China, and phylogenetic relationships of early actinopterygian fishes. Vertebrata PalAsiatica, 59(3), 169-199.
Xu, G. H., Ma, X. Y., & Zhao, L. J. (2018). A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China. Vertebrata PalAsiatica, 56(2), 106-120.
Betancur-R, R., Wiley, E. O., Arratia, G., Acero, A., Bailly, N., Miya, M., ... & Orti, G. (2017). Phylogenetic classification of bony fishes. BMC evolutionary biology, 17(1), 1-40.
Figueroa, R. T., Friedman, M., & Gallo, V. (2019). Cranial anatomy of the predatory actinopterygian Brazilichthys macrognathus from the Permian (Cisuralian) Pedra de Fogo Formation, Parnaíba Basin, Brazil. Journal of Vertebrate Paleontology, 39(3), e1639722.
Giles, S., Xu, G. H., Near, T. J., & Friedman, M. (2017). Early members of ‘living fossil’lineage imply later origin of modern ray-finned fishes. Nature, 549(7671), 265.
Near, T. J., Eytan, R. I., Dornburg, A., Kuhn, K. L., Moore, J. A., Davis, M. P., ... & Smith, W. L. (2012). Resolution of ray-finned fish phylogeny and timing of diversification. Proceedings of the National Academy of Sciences, 109(34), 13698-13703.
Ren, Y., & Xu, G. H. (2021). A new species of Pteronisculus from the Middle Triassic (Anisian) of Luoping, Yunnan, China, and phylogenetic relationships of early actinopterygian fishes. Vertebrata PalAsiatica, 59(3), 169-199.
Xu, G. H., Ma, X. Y., & Zhao, L. J. (2018). A large peltopleurid fish (Actinopterygii: Peltopleuriformes) from the Middle Triassic of Yunnan and Guizhou, China. Vertebrata PalAsiatica, 56(2), 106-120.