BONE AND TOOTH MICROSTRUCTURE IN EXTINCT AND EXTANT MAMMALS AND IMPLICATIONS FOR GROWTH AND LIFE HISTORY EVOLUTION, WITH AN EMPHASIS ON CERVIDS AS A CASE STUDY

KOLB, CH.; SCHEYER. T.M.; AMSON, E.; VEITSCHEGGER, K.; FORASIEPI, A.M.; SANCHEZ-VILLAGRA M.

Buenos Aires

Jornada; XXX Jornadas Argentinas de Paleontologia de Vertebrados; 2016

Museo Argentino de Ciencias Naturales B. Rivadavia

There is much body size diversity within mammals, more so if we consider extinct species. The developmental and life history changes behind this evolutionary pattern are a rich subject of investigation, and bone and tooth microstructure are markers of such a pattern. The knowledge and methods on synapsid bone microstructure and palaeohistology, presenting a large variety of bone tissues, are reviewed. New bone histological data on marsupials and on several extinct mainland and island placental mammals are presented. Cervids represent an ideal case study clade for exploring body size and life history evolution, as they are characterised by a rich fossil record, a generally well-known phylogeny, and exceptional examples of body size evolution. The hard tissue histology of various cervid species, including the genus Candiacervus with dwarf morphotypes from the Pleistocene of Crete, and the extinct giant deer Megaloceros giganteus, both closely related to the recent fallow deer, Dama dama, was examined. Dwarf Candiacervus are characterised by low absolute growth rates, Megaloceros giganteus by high rates. Tooth cementum analysis reveals that in an allometric context, dwarf Candiacervus had an extended lifespan compared to deer of similar body size. Histological traits of sampled island and continental mammals suggest the presence of various modes of life history modifications to depend on ecological factors, time of evolution, and phylogeny. Comparison of cervid long bone compactness parameters suggests that mass saving is less intensively selected in zeugopodial bones. Dwarf Candiacervus feature relatively thick cortices, suggesting decoupling between limb shortening and mid-diaphyseal cortical thickness.