Of bones and teeth: using cross-calibrated histology to infer physiology in mammal ancestors

We plan to investigate growth and physiology in extinct mammalian ancestors using synchrotron tomography to image their fossil bones and teeth at sub-micron resolution. Our experiment will combine the complimentary histological growth records preserved in teeth and bones. Our proposed study system are five species of South African cynodonts close to mammalian origins that lived some 200 million years ago. These species are known from numerous exquisitely preserved fossils, including juveniles and presumed adults, permitting insight across their growth history. Scans of dentine and enamel of their teeth will image daily-to-monthly growth increments, and will be calibrated to circum-annual increments in the tooth cementum, and annual lines of arrested growth in long bones and jaws. These data, alongside analysis of long-bone histological fabrics, will provide the highest-resolution histological insights for life history in fossil samples to-date.