Modern Data on the Origin and Early Radiation of Mammals

Abstract

Modern fossil evidence shows extensive ecomorphological radiation of Mesozoic mammals. By the mid-Cretaceous, mammals had evolved all the main adaptations of modern small-sized Mammalia except for true powered flight. In addition, new paleontological and embryological data on the morphogenesis of the auditory ossicles demonstrate parallel developments of the definitive mammal middle ear in the placentals, marsupials, and monotremes, as well as the independent origins of a number of early groups: Allotheria (Haramiyida and Multituberculata) within Mammaliamorpha (irrespective of the lineage including eucynodonts Brasilodontidae and the mammaliaform Apotheria, Prototheria, and Acrotheria) and Prototheria (including Monotremata) within the Mammaliaformes (parallel to the Acrotheria lineage).