The ancestor of sharks and rays laid eggs, but ancestral state reconstructions need empirically supported traits and transparent reporting: a comment on Katona et al. (2023).

This article critically examines discrepancies between two recent phylogenetic studies on the evolution of reproductive modes in chondrichthyan fishes (sharks and rays), focusing on ancestral state reconstructions. It identifies that the study by Katona et al. (2023) relied heavily on secondary, high-level literature sources lacking species-specific data, leading to numerous questionable or unsupported assignments of reproductive traits and ambiguous methodological reporting. In contrast, Blackburn and Hughes (2024) used extensive primary literature to provide more reliable species-level reproductive data, resulting in fewer inferred evolutionary transformations and no reversals from viviparity to oviparity. Reanalyses of Katona et al.’s data with corrected trait assignments and consistent phylogenetic frameworks reduced but did not eliminate discrepancies, underscoring the importance of accurate trait coding, transparent methodology, and appropriate phylogenetic use in evolutionary studies. The authors recommend rigorous data sourcing, clear reporting, and careful trait coding to improve the reliability of ancestral state reconstructions in evolutionary biology.