Using synchrotron to examine the earliest life history evolution of modern mammal groups: tracking canalisation and diversity through X-ray

Modern mammal groups are characterized by distinct life-history traits. Our team’s recent studies have shown these traits can be tracked in the fossil record using X-ray micro-tomographic (μCT) techniques to analyse the histology of teeth and bones. We propose sampling fossil mammals from the early–mid Paleogene (~60–35 Ma), and hypothesize this interval witnessed an important calanisation event, underpinning the emergence and diversification of modern placental and marsupial orders. We will obtain estimates of longevity (from cementum) and gestation and lactation durations (from enamel), and proxies for relative postnatal vs. prenatal developmental investment (from bone histology) based on proportions of perinatal vs. postnatal tissues in the bone cortex. These data, in addition to phylogenetic generalized least-squares regressions and MANOVA analyses, will allow us to test whether fossil representatives of modern orders correspond physiologically with their extant counterparts.