Lancian

Abstract: A series of Cretaceous mammal faunas, beginning with standard late Cretaceous faunas and continuing with three of Paleocene aspect, are summarized. Four families (Eucosmodontidae, Taeniolabididae, Leptictidae, Arctocyonidae) and one order (Condylarthra) of Tertiary mammals are extended into the Cretaceous. New genera Cimexomys, Stygimys, Procerberus, and Protungulatum are described, as is a small species of Catopsalis. The skeleton of a multituberculate is restored and multituberculate classification is revised.

Abstract: Mammalian faunas are documented for the first time from the \"Mesaverde\" Formation (Late Cretaceous) ofWyoming. Nonmarine fossils from the Bighorn and Wind River basins indicate a Judithian (revised definition) \"age\" for the assemblages through comparisons with approximately contemporaneous faunas of the Judith River (Montana) and Oldman (Alberta) formations. Three previously unknown genera are recognized, although not named herein, from the \"Mesaverde\" Formation (Multituberculata, new genus and species, unidentified; Dryolestidae, new genus and species, unidentified; and Falepetrus barwini). Three new species of previously described genera (Alphadon sahnii, A. attaragos, and Paranyctoides megakeros) are named. All species-level taxa (16 total) except Alphadon lulli are reported from Wyoming for the first time, and new records involve both geographic and geologic range extensions. The temporal record ofthe dryolestid appears relictual, being preyiouslyunknown from post-Jurassic strata in North America. Tax6nomic comparisons suggest that the Judithian mammalian fauna of what was then coastal parts of the western interior was essentially homogeneous geographically, at least from southern Alberta to central Wyoming. Nonmarine mammalian assemblages from the Oldman, Judith River, and \"Mesaverde\" formations correlate temporally with more easterly marine rock units that lie within (or within four zones above) the Baculites gregoryensis (cephalopod) Zone, part ofthe standard zonation ofUpper Cretaceous rocks of the North American western interior. The upper part of the Red Bird Silty Mem' Professor, Departments of Geology and Geophysics/Zoology and Physiology, The University of Wyoming, Laramie, Wyoming 82071. 2 Frick Curator of Fossil Mammals, Department of Vertebrate Paleontology, The American Museum of Natural History; Professor, Department of Geological Sciences, Columbia University. Copyright © American Museum of Natural History 1986 ISSN 0003-0082 / Price $5.50 AMERICAN MUSEUM NOVITATES ber ofthe Pierre Shale at Redbird, Wyoming, holds the largely endemic invertebrate macrofaunal assemblage characteristic ofthe B. gregoryensisZone as well as a newly described planktonic foraminiferal assemblage. The microfossils allow correlation to the upper Taylorian and/or lower Navarroan foraminiferal stages of the Gulf Coast. This, in turn, correlates approximately to the Campanian-Maastrichtian stage boundary at Gubbio, Italy, and European stratotypic sections. Judithian mammal faunas of the Rocky Mountains, therefore, must be younger in age (i.e., late Campanian and/or early Maastrichtian) in terms of the European stages than usually is considered on the basis of molluscan zonations within the North American western interior (e.g., well within the Campanian). Judithian mammals from the Rockies probably lived about 74-76 million years ago during the late part of geomagnetic Polarity Chron 33 or the early part of Polarity Chron 32, during the regressive phases of the Claggett cyclothem as recognized for the western shoreline of the Western Interior Seaway. They correlate stratigraphically with the lower part of the Aquilapollenites quadrilobus palynomorph Interval Zone of the northern Rockies. Aquilan (oldest), Judithian, and Lancian (youngest) provincial North American land-mammal \"ages\" are redefined for the Late Cretaceous nonmarine sequence of the western interior from an older stage concept; the \"ages,\" based upon species-level mammalian assemblages, are modeled after the system used successfully for nonmarine Cenozoic faunas of North America. An Edmontonian \"age\" (previously used as a stage term, chronologically intermediate between the Judithian and Lancian) is probably identifiable as a discrete interval of geologic time, but is not yet defensible on the basis of mammalian assemblages. Therefore, it is not redefined as a landmammal \"age.\" We concur with the interpretation that the Djadokhta Formation of southern Mongolia and the Judith River and Oldman faunas of North America are essentially ofthe same age. This compresses the faunas of the Barun Goyot and Nemegt formations of southern Mongolia, plus that of the poorly known, nearby Bugeen Tsav locality, into an interval of time equivalent to the Judithian and/or Lancian North American land mammal \"ages\" and, most probably, to the Maastrichtian stage as typified in western Europe.

Abstract: Bug Creek assemblages from Montana, transitional in composition between typical Cretaceous and Paleocene vertebrate faunas, are critical to K-T extinction debates because they have been used to support both gradual and catastrophic K-T extinction scenarios. Geological and palynological data from McGuire Creek indicate that Bug Creek assemblages are Paleocene and restricted to channel fills entrenched into older sediments, suggesting that the Cretaceous component of the assemblage was reworked. Thus, the author concludes, "Paleocene dinosaurs" are an illusion and the K-T survival rate of mammals is low because the presence of Cretaceous mammals in Bug Creek assemblages is also the result of reworking.

Abstract: The earliest unquestionable records of Purgatorius (Plesiadapiformes, Primates?, Mammalia) in northeastern Montana and other areas of the Western Interior of North America are of early Paleocene, specifically middle or late Puercan (Pu 2–3 Interval Zones, undifferentiated) North American Land Mammal Age (NALMA). The report of an occurrence of Purgatorius in the Late Cretaceous (Lancian NALMA) was based on an isolated, worn lower molar found in a channel filling that is now recognized as containing a time-averaged assemblage of Lancian and earliest Puercan (Pu 1 Interval Zone) fossils. Purgatorius has not been found in large samples of other local faunas of either Pu 1 or Lancian age. In contrast, Purgatorius is abundantly represented in Pu 2–3 local faunas in the northern Western Interior suggesting that it dispersed into the area during the interval between ca. 64.75 and 64.11 Ma. Fragmentary dentaries provisionally referred to Purgatorius janisae from the Garbani Channel fauna (Pu 2–3) document...