\u3ci\u3eMylanodon rosei\u3c/i\u3e, a New Metacheiromyid (Mammalia: Palaeanodonta) from the Late Tiffanian (Late Paleocene) of Northwestern Wyoming

Mylanodon rosei is a new genus and species of late Paleocene metacheiromyid palaeanodont from a new late Tiffanian locality, Y2K Quarry, in the Clarks Fork Basin, Wyoming. The type is an adult dentary with P4 and a molariform double-rooted M1. This provides the first evidence that molariform teeth were retained in early Metacheiromyidae. A second specimen is a juvenile dentary with a partial P3 and an unerupted P4. This is the first juvenile dentition known for a Paleocene metacheiromyid. The new specimens enable determination of dental homologies. Reduction of teeth in early metacheiromyids took place from back to front, opening the characteristic posterior diastema. Both Mylanodon and Propalaeanodon, a slightly older metacheiromyid, are intermediate morphologically and temporally between the older Tiffanian epoicotheriid Amelotabes and the younger Clarkforkian and Wasatchian metacheiromyid Palaeanodon. Propalaeanodon has a single-rooted M1, a derived characteristic not found in Mylanodon, suggesting that two lineages are involved and Propalaeanodon was not ancestral to Mylanodon

Statistics of Solar Wind Electron Breakpoint Energies Using Machine Learning Techniques

Solar wind electron velocity distributions at 1 au consist of a thermal "core" population and two suprathermal populations: "halo" and "strahl". The core and halo are quasi-isotropic, whereas the strahl typically travels radially outwards along the parallel and/or anti-parallel direction with respect to the interplanetary magnetic field. With Cluster-PEACE data, we analyse energy and pitch angle distributions and use machine learning techniques to provide robust classifications of these solar wind populations. Initially, we use unsupervised algorithms to classify halo and strahl differential energy flux distributions to allow us to calculate relative number densities, which are of the same order as previous results. Subsequently, we apply unsupervised algorithms to phase space density distributions over ten years to study the variation of halo and strahl breakpoint energies with solar wind parameters. In our statistical study, we find both halo and strahl suprathermal breakpoint energies display a significant increase with core temperature, with the halo exhibiting a more positive correlation than the strahl. We conclude low energy strahl electrons are scattering into the core at perpendicular pitch angles. This increases the number of Coulomb collisions and extends the perpendicular core population to higher energies, resulting in a larger difference between halo and strahl breakpoint energies at higher core temperatures. Statistically, the locations of both suprathermal breakpoint energies decrease with increasing solar wind speed. In the case of halo breakpoint energy, we observe two distinct profiles above and below 500 km/s. We relate this to the difference in origin of fast and slow solar wind.Comment: Published in Astronomy & Astrophysics, 11 pages, 10 figure

Carpolestes simpsoni, New Species (Mammalia, Proprimates) from the Late Paleocene of the Clark's Fork Basin, Wyoming

131-162http://deepblue.lib.umich.edu/bitstream/2027.42/48654/2/ID521.pd

Oldest Skeleton of a Plesiadapiform provides additional evidence for an exclusively arboreal radiation of stem Primates in the Palaeocene

Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptive scenarios for primate origins for nearly a half-century. Likewise, palaechthonids have been considered important for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the first Palaechthonid plesiadapiforms from the Palaeocene of western North America have long been recognized as among the oldest and most primitive euarchontan mammals, a group that includes extant primates, colugos and treeshrews. Despite their relatively sparse fossil record, palaechthonids have played an important role in discussions surrounding adaptive scenarios for primate origins for nearly a half-century. Likewise, palaechthonids have been considered important for understanding relationships among plesiadapiforms, with members of the group proposed as plausible ancestors of Paromomyidae and Microsyopidae. Here, we describe a dentally associated partial skeleton of Torrejonia wilsoni from the early Palaeocene (approx. 62Ma) of New Mexico, which is the oldest known plesiadapiform skeleton and the firs

Cranial Anatomy of the Earliest Marsupials and the Origin of Opossums

BACKGROUND: The early evolution of living marsupials is poorly understood in part because the early offshoots of this group are known almost exclusively from jaws and teeth. Filling this gap is essential for a better understanding of the phylogenetic relationships among living marsupials, the biogeographic pathways that led to their current distribution as well as the successive evolutionary steps that led to their current diversity, habits and various specializations that distinguish them from placental mammals. METHODOLOGY/PRINCIPAL FINDINGS: Here we report the first skull of a 55 million year old peradectid marsupial from the early Eocene of North America and exceptionally preserved skeletons of an Oligocene herpetotheriid, both representing critical groups to understand early marsupial evolution. A comprehensive phylogenetic cladistic analysis of Marsupialia including the new findings and close relatives of marsupials show that peradectids are the sister group of living opossums and herpetotheriids are the sister group of all living marsupials. CONCLUSIONS/SIGNIFICANCE: The results imply that North America played an important role in early Cenozoic marsupial evolutionary history and may have even been the center of origin of living marsupials and opossums. New data from the herpetotheriid postcranium support the view that the ancestral morphotype of Marsupialia was more terrestrial than opossums are. The resolution of the phylogenetic position of peradectids reveals an older calibration point for molecular estimates of divergence times among living marsupials than those currently used

Mylanodon rosei, a new metacheiromyid (Mammalia, Palaeanodonta) from the late Tiffinian (late Paleocene) of northwestern Wyoming

385-399http://deepblue.lib.umich.edu/bitstream/2027.42/48666/2/ID533.pd

Systematics and Phylogeny of Late Paleocene and Early Eocene Palaeoryctinae (Mammalia, Insectivora) from the Clarks Fork and Bighorn Basins, Wyoming

p. 119-154http://deepblue.lib.umich.edu/bitstream/2027.42/41252/1/C31-5.pd

New Primates (Mammalia) From The Early and Middle Eocene Of Pakistan And Their Paleobiogeographical Implications

http://deepblue.lib.umich.edu/bitstream/2027.42/61363/1/GunnellContributions32 no1.pd

New species of Macrocranion (Mammalia, Lipotyphla) from the earliest Eocene of North America and its biogeographic implications

373-384http://deepblue.lib.umich.edu/bitstream/2027.42/48665/2/ID532.pd