Biomineralization by particle attachment in early animals*

Crystallization by particle attachment (CPA)¹ of amorphous calcium carbonate (ACC) was demonstrated in modern biominerals from diverse animals. Precisely the same precursors, hydrated and anhydrous ACC, have been observed spectromicroscopically in echinoderms^2-4, molluscs⁵, cnidarians⁶. This is surprising, as these three phyla have no common ancestor that formed biominerals, and have, therefore, evolved carbonate biomineralization independently ~100 million years after diverging from one another⁷. Here we correlate the occurrence of CPA of ACC precursor particles with nanoparticulate fabric and then use the latter to investigate the antiquity of the former. SEM images of the oldest known animal biominerals show that these animals used attachment of ACC particles to form their biominerals. The convergent evolution of biomineral CPA may have been dictated by the same thermodynamics and kinetics as we observe today.
1 JJ De Yoreo 2015 DOI: 10.1126/science.aaa6760
2 Y Politi 2008 DOI: 10.1073/pnas.0806604105
3 YUT Gong 2012 DOI: 10.1073/pnas.1118085109
4 M Albéric 2019 DOI: 10.1016/j.yjsbx.2019.100004
5 RT DeVol 2015 DOI: 10.1021/jacs.5b07931
6 T Mass 2017 DOI: 10.1073/pnas.1707890114
7 PUPA Gilbert 2019 doi/10.1073/pnas.1902273116