Judithian

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: The Terlingua local fauna is a rich assemblage of predominantly terrestrial micro vertebrates from the Upper Cretaceous Aguja Formation of Trans-Pecos Texas. Marine invertebrates (which include elements of both Cretaceous Western Interior and Gulf Coast zoogeographic provinces) from conformably underlying strata suggest that the fauna is of late Campanian age, probably correlative with Judithian assemblages of the Western Interior. A Judithian “age” for the fauna is further supported by its mammal and theropod assemblages, and by the faunas of overlying deposits. The previously reported diversity of the Aguja Formation, which we summarize, is significantly enriched by this new fauna. The fauna also fills a major gap in the biogeography of Campanian terrestrial vertebrates. Notable occurrences in the Terlingua local fauna include the therian mammal Gallolestes, previously known only from Baja California, and a hitherto unrecorded type of primitive ‘tribothere.’ At least 4 marsupial and 6 multitube...

Abstract: Newly described marsupial specimens of Judithian (late Campanian) and Lancian (Maastrichtian) age in the western interior of North America (Wyoming to Alberta) have dental morphologies consistent with those expected in comparably aged sediments in South America (yet to be found). Three new Lancian species are referable to the didelphimorphian Herpetotheriidae, which suggests that the ameridelphian radiation was well under way by this time. The presence of a polydolopimorphian from Lancian deposits with a relatively plesiomorphic dental morphology and an additional polydolopimorphian taxon from Judithian deposits with a more derived molar form indicate that this lineage of typically South American marsupials was diversifying in the Late Cretaceous of North America. This study indicates that typical South American lineages (e.g. didelphimorphians and polydolopimorphians) are not the result of North American peradectian progenitors dispersing into South America at the end of the Cretaceous (Lancian), or at the beginning of the Paleocene (Puercan), and giving rise to the ameridelphian marsupials. Instead, these lineages, and predictably others as well, had their origins in North America (probably in more southerly latitudes) and then dispersed into South America by the end of the Cretaceous. Geophysical evidence concerning the connections between North and South America in the Late Cretaceous is summarized as to the potential for overland mammalian dispersal between these places at those times. Paleoclimatic reconstructions are considered, as is the dispersal history of hadrosaurine dinosaurs and boid snakes, as to their contribution to an appraisal of mammalian dispersals in the Late Cretaceous. In addition, we present a revision of the South American component of the Marsupialia. One major outcome of this process is that the Polydolopimorphia is placed as Supercohort Marsupialia incertae sedis because no characteristics currently known from this clade securely place it within one of the three named marsupial cohorts.

Abstract: The Kirtlandian land-vertebrate “age” (LVA) is equivalent to 2.2 million years of Campanian time and fills a long-standing biochronologic gap between the Judithian and Edmontonian LVAs. The Kirtlandian is characterized by the vertebrate fossil assemblages of the Fruitland and Kirtland formations, San Juan Basin, New Mexico. Pentaceratops sternbergii, a ceratopsid taxon, is the principal index fossil. Other index fossils are the hadrosaur taxa Parasaurolophus cyrtocristatus and Kritosaurus navajovius. Unique taxa include: Melvius chauliodous, Denazinemys ornata, Boremys grandis, Adocus bossi, A. kirtlandius, Neurankylus baueri, Thescelus hemispherica, Aspideretes ovatus, “Plastomenus” robustus, Denazinosuchus kirtlandicus, Saurornitholestes robustus, Anasazisaurus horneri, Kritosaurus navajovius, Naashoibitosaurus ostromi, Parasaurolophus cyrtocristatus, P. tubicen, Nodocephalosaurus kirtlandensis, Kritosaurus navajovius, Prenocephale goodwini and Pentaceratops sternbergii. The Kirtlandian LVA is defined as the time between the first appearance of Pentaceratops sternbergii (= end of the Judithian) and the first appearance of Edmontosaurus regalis (= beginning of the Edmontonian). Principal correlatives of the characteristic Kirtlandian vertebrate assemblage are the vertebrate faunas of the lower part of the Bearpaw Formation of Montana, USA and Alberta, Canada; Williams Fork Formation, northwestern Colorado; upper part of the Kaiparowits Formation, south-central Utah; Fort Crittenden Formation, southeastern Arizona, Ringbone Formation, southwestern New Mexico; Corral de Enmedio and Packard formations of the Cabullona Group, Sonora, Mexico; El Gallo Formation, Baja California del Norte, Mexico; and possibly the lower part of the Cerro del Pueblo Formation, Coahuila, Mexico. The upper shale member of the Aguja Formation, Big Bend region, Texas, may be correlative to part of the Kirtlandian based on recently published radioisotopic dates. Recognition of the Kirtlandian undermines the concept of two paleogeographically distinct dinosaur paleocommunities in the Western Interior during the late Campanian. Thus, more precise vertebrate biochronology indicates that vertebrate assemblages previously considered characteristic of northern and southern provinces are not coeval; the differences are thus temporal, not biogeographic origin.