2026-07-02 シカゴ大学
CT scan image of the entire interior skeleton of Trawdenia planti contained in the nodule.Scan by Kristen Tietjen
＜関連情報＞
- https://news.uchicago.edu/story/fossil-fish-preserved-brain-sheds-light-bottom-evolutionary-tree
- https://www.pnas.org/doi/10.1073/pnas.2610438123
石炭紀条鰭類の神経組織と軟骨硬骨の特徴 Neural tissues and chondrostean traits in a Carboniferous actinopterygian
Abigail M. Caron, Kristen Tietjen, and Michael I. Coates
Proceedings of the National Academy of Sciences Published:June 29, 2026
DOI:https://doi.org/10.1073/pnas.2610438123
Abstract
Ray-finned fishes (Actinopterygii) represent over half of extant vertebrate species, but their early evolutionary history is largely unresolved. Current phylogenetic estimates, corroborated by discoveries of preserved neural tissues, place most Palaeozoic actinopterygians outside the crown group and leave the deep roots of major extant divisions depauperate. Moreover, apparent fossil brains in early fishes are minuscule relative to endocranial chamber space, implying that endocasts are poor indicators of neuroanatomical gross morphology. Here, through X-ray micro-computed tomography of the early actinopterygian Trawdenia planti, we show unexpected neurocranial and neural soft tissue morphology indicative of a large brain fitting snugly within the endocranium. We find internal ventricular structures, present a model of neural tissue preservation, identify neuroanatomical characters, and demonstrate that endocasts capture phylogenetically and ecologically informative signal. These data suggest that Trawdenia bridges the gap between early actinopterygians and modern Chondrostei, thereby offering an alternative framework for understanding early actinopterygian neural evolution that departs radically from current phylogenetic hypotheses.
