Controlled hydroxyapatite biomineralization in an ~810 million year old unicellular eukaryote

Biomineralization marks one of the most significant evolutionary milestones among the eukarya, but its roots in the fossil record remain obscure. Here, we report crystallographic and geochemical evidence for controlled eukaryotic biomineralization in Neoproterozoic scale microfossils from Manuscript Click here to download Manuscript Cohen et al Science Advances 4-20_nocode.docx Science Advances Manuscript Template Page 2 of 23 the Fifteenmile Group of Yukon, Canada. High-resolution transmission electron microscopy reveals that the microfossils are constructed of a hierarchically organized interwoven network of fibrous hydroxyapatite crystals each elongated along the [001] direction, indicating biological control over microstructural crystallization. New Re-Os geochronological data from organic-rich shale directly below the fossil-bearing limestone constrain their age to < 810.7 ± 6.3 Ma. Mineralogical and geochemical variations from these sedimentary rocks indicate that dynamic global marine redox conditions, enhanced by local restriction, may have led to an increase in dissolved phosphate in pore and bottom waters of the Fifteenmile basin and facilitated the necessary geochemical conditions for the advent of calcium phosphate biomineralization