Article: Linking evolution and development: Synchrotron Radiation X-ray tomographic microscopy of planktic foraminifers

Making the link between evolutionary processes and development in extinct organisms is usually hampered by the lack of preservation of ontogenetic stages in the fossil record. Planktic foraminifers, which grow by adding chambers, are an ideal target organism for such studies as their test incorporates all prior developmental stages. Previously, studies of development in these organisms were limited by the small size of their early chambers. Here, we describe the application of synchrotron radiation X-ray tomographic microscopy (SRXTM) to document the ontogenetic history of the foraminifers Globigerinoides sacculifer and Globorotalia menardii. Our SRXTM scans permit resolution at submicrometre scale, thereby displaying additional internal structures such as pores, dissolution patterns and complexity of the wall growth. Our methods provide a powerful tool to pick apart the developmental history of these microfossils and subsequently assist in inferring phylogenetic relationships and evolutionary processes.