n. sp.: a novel predatory flagellate illuminates the character evolution within the eukaryotic clade CRuMs.

Culturing protists offers a powerful approach to exploring eukaryotic diversity, especially for deep-branching lineages. In this study, we cultured and described a novel protist species, named n sp. within the poorly studied and unclassified genus . While an SSU rDNA gene phylogeny failed to resolve its phylogenetic placement in the eukaryotic tree, a phylogenomic analysis of 340 proteins indicated as a member of the CRuMs clade. Prior to this study, this clade consisted of diverse heterotrophic amoeba and flagellates, and lacked clear synapomorphies. Ultrastructural observations revealed that shares the characteristics with some CRuMs members, including the pellicle underlying the plasma membrane and an internal sleeve surrounding the central pair of the axoneme at the flagellar transitional region. Our findings suggest potential shared characteristics and synapomorphies for CRuMs and contribute to a deeper understanding of the character evolution within this clade.