Using long bone histology to illuminate the emergence of mammal reproductive life histories

This study will identify long-term evolutionary developments in mammal reproductive strategy, reflected in the microstructures of long bones. These strategies have fundamentally influenced the macroevolution of mammals since their emergence in the Mesozoic, but the timing and pattern of their emergence remains one of the major unanswered questions in palaeontology. Our study of histological microstructures in the femora and humeri of early mammals will be compared with representatives of the three major groups of living mammals: placentals, marsupials, and monotremes. Previous studies were restricted in terms of sample size and taxonomy due to the destructive nature of traditional histological preparation techniques. The use of non-destructive SRCT mapping will permit us to examine a broad collection of fossil mammals spanning the Late Triassic (~205 mya) to Late Cretaceous (90 mya), as well as extant monotremes – the latter omitted from previous studies.