Eocene scaled chrysophytes with pronounced modern affinities

This is the first documentation of scaled chrysophytes of Tertiary age. Siliceous scales belonging to four genera (Synura, Mallomonas, Chrysosphaerella, and Spiniferomonas) are preserved in middle Eocene (similar to 47 Ma) lacustrine mudstones deposited in a posteruptive crater associated with kimberlite intrusion near Lac de Gras, Northwest Territories, Canada. Astonishingly, most of these microfossils have remarkable morphological affinities with extant congeneric taxa, indicating that the unique siliceous ornamentation of the scaled chrysophytes, including scales, spines, and bristles, was fully evolved by the middle Eocene. These observations imply that the scaled chrysophytes experienced prolonged intervals of relative evolutionary stasis during Neogene and Quaternary times and thus provide a new evolutionary milepost for this algal group.