A single freshwater invasion gave rise to the world's dominant freshwater fish group

Otophysa’s diversification is linked to a marine origin in only 6 of 132 biogeographic analyses, and only under fossil placements inconsistent with the new phylogeny.

• Why it matters: Competing claims about whether otophysans arose from parallel freshwater invasions or a single marine-to-freshwater transition hinge on uncertain fragmentary fossils and model choices.
• What they did: The study adds a first phylogenetic analysis of the marine fossil genus Sooinichthys and re-evaluates Santanichthys, then reanalyzes Liu et al.’s genomic dataset with expanded sampling and multiple biogeographic models.
• The result: The evidence instead supports a single freshwater invasion scenario for otophysan diversification and warns that sparse sampling, taphonomic bias, and fossil overinterpretation can create false biogeographic narratives.

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