Deep time diversity of metatherian mammals: implications for evolutionary history and fossil-record quality

—Despite a global fossil record, Metatheria are now largely restricted to Australasia and South America. Most metatherian paleodiversity studies to date are limited to particular subclades, time intervals, and/or regions, and few consider uneven sampling. Here, we present a comprehensive new data set on metatherian fossil occurrences (Barremian to end Pliocene). These data are analyzed using standard rarefaction and shareholder quorum subsampling (including a new protocol for handling Lagerstätte-like localities). Global metatherian diversity was lowest during the Cretaceous, and increased sharply in the Paleocene, when the South American record begins. Global and South American diversity rose in the early Eocene then fell in the late Eocene, in contrast to the North American pattern. In the Oligocene, diversity declined in the Americas, but this was more than offset by Oligocene radiations in Australia. Diversity continued to decrease in Laurasia, with final representatives in North America (excluding the later entry of Didelphis virginiana) and Europe in the early Miocene, and Asia in the middle Miocene. Global metatherian diversity appears to have peaked in the early Miocene, especially in Australia. Following a trough in the late Miocene, the Pliocene saw another increase in global diversity. By this time, metatherian biogeographic distribution had essentially contracted to that of today. Comparison of the raw and sampling-corrected diversity estimates, coupled with evaluation of “coverage” and number of prolific sites, demonstrates that the metatherian fossil record is spatially and temporally extremely patchy. Therefore, assessments of macroevolutionary patterns based on the raw fossil record (as in most previous studies) are inadvisable. C. Verity Bennett. Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, United Kingdom. E-mail: [email protected]. Present address: Division of Population Medicine, Cardiff University, Heath Park, Cardiff CF14 4YS, United Kingdom. Paul Upchurch. Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, United Kingdom. E-mail: [email protected] Francisco J. Goin. CONICET—División Paleontología Vertebrados, Museo de La Plata, La Plata, Argentina. E-mail: [email protected] Anjali Goswami. Department of Genetics, Evolution and Environment and Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, United Kingdom. E-mail: [email protected]. Present address: Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD. Accepted: 16 October 2017 Data available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.bt651