Chrysochromulina: Genomic assessment and taxonomic diagnosis of the type species for an oleaginous algal clade

•Genetic assessment supports revisiting the Diagnosis for the Chrysochromulina clade.•Chrysochromulina isolates share extensive morphology but differ genetically; thus, cryptic species complexes are described.•Fresh water Chrysochromulina isolates appear to have all the genes that insure sexual reproductive capability.•These data provide a primary database for probing the functional specialization among haptophytes and other algal lineages.