[...]... that affect the interpretation of that record These include the timing of the radiation, how phylogenetic relationships are established, the interrelationships and classification of mammals, and the chronologic framework of the Early Cenozoic TIMING OF THE CROWN-THERIAN RADIATION The question of when the therian radiation took place is a contentious issue, whose answer depends on the kind of data employed—paleontological... Madagascar and begun its drift northward The rest of Asia was a large landmass separated from Europe by an epicontinental seaway (the Obik Sea to the north and the Turgai Straits at the southern end), which joined the Arctic Ocean to the Tethys Sea This was the paleogeographic setting at the beginning of the Age of Mammals Interchange of land mammals between any of the landmasses separated by marine barriers... the K/T boundary as after it, yet the fossil evidence suggests that only the multituberculates radiated widely during the Mesozoic The Mesozoic was the heyday of multituberculates They shared the Earth with dinosaurs for 90 million years or more, becoming diverse and abundant in many northern faunas, only to be outcompeted by other mammals before the end of the Eocene Even those other mammals metatherians... reproduce the best available illustrations of a wide diversity of fossil mammals The drawback of this approach is that multiple styles of illustration are often combined in the same composite figure However, I believe the benefit of using original illustrations significantly outweighs the aesthetic of redrawing them all in the same style, with its inherent risk of introducing inaccuracies For ease of comparison,... OF THE AGE OF MAMMALS The evolution and dispersal of mammals during the early Cenozoic were strongly influenced by the positions of the 18 the beginning of the age of mammals continental plates, the connections among them, the amount and distribution of subaerial exposure, and the marine barriers separating or dividing continents The salient aspects of paleogeography at that time summarized here are based... on the mammalian radiation during the Paleocene and Eocene epochs, essentially the first half of the Cenozoic Era Although this radiation has attracted far less popular interest than that of dinosaurs, it was a pivotal interval in the history of vertebrates, which set the stage for 1 2 the beginning of the age of mammals the present-day mammalian fauna, as well as our own evolution At its start, the. .. twothirds of the 35 families of Late Cretaceous mammals listed by McKenna and Bell (1997) disappeared at the end of the Cretaceous In the northern Western Interior of North America, mammalian extinctions were even more severe, affecting 80–90% of lineages (Clemens, 2002) A small number of clades crossed the Cretaceous/Tertiary (K/T) boundary, most notably, several lineages of multituberculates, eutherians,... Chelsea—for their unwavering faith in me and their steadfast encouragement throughout the long gestation of this project, especially when it seemed unachievable They are to be credited with its completion The Beginning of the Age of Mammals This page intentionally left blank 1 Introduction M AMMALS ARE AMONG THE MOST successful animals on earth They occupy every major habitat from the equator to the poles,... summarize current knowledge of the record of this extensive PaleoceneEocene radiation and the roles of mammals in the world of the Early Cenozoic, which are essential for understanding the structure and composition of present-day ecosystems This volume focuses on the fossil evidence of these early mammals and what their anatomy indicates about interrelationships, evolution, and ways of life First it is necessary,... been found in the early Paleocene On a more local level, Lofgren (1995) reported that the survival rate of mammalian species across the K/T boundary in the Hell Creek area of Montana was only about 10% Introduction 3 Fig 1.1 Family diversity of mammals from the Cretaceous to the present Bars indicate the number of families recorded from each interval; the shaded portion denotes the number of those families . class="bi x0 y0 w0 h0" alt="" The Beginning of the Age of Mammals The Beginning of the Age of Mammals KENNETH D. ROSE THE JOHNS HOPKINS UNIVERSITY PRESS, Baltimore © 2006 The Johns Hopkins University. many northern faunas, only to be out- competed by other mammals before the end of the Eocene. Even those other mammals metatherians and eutherians (often grouped as therians, or crown therians)—had. syn- thesized basic data on the extant mammals together with a survey of the rapidly improving mammalian fossil record to provide an overview of mammalian evolu- tion. The Beginning of the Age of