90 research outputs found

    Skeleton of Alocodontulum atopum, An Early Eocene Epoicotheriid (Mammalia, Palaeanodonta) from the Bighorn Basin, Wyoming

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    221-245http://deepblue.lib.umich.edu/bitstream/2027.42/48546/2/ID400.pd

    Cricetid

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    14 p. : ill. ; 24 cm.Includes bibliographical references (p. 13-14)."Two specimens, a partial right mandibular ramus with M[subscript 1]-M[subscript 3] and an isolated left M[subscript 2], represent a new genus and species of rodent, Nanomys simplicidens. The teeth of this rodent are so lacking in special characters that its phylogenetic position is difficult to interpret, but it seems best referred to the Cricetidae"--P. [1]

    Relationships of Apternodus

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    117 p. : ill., map ; 26 cm.Includes bibliographical references (p. 110-117).We describe and illustrate new, middle Cenozoic fossils of dentally zalambdodont, North American placentals, including six relatively complete crania of Apternodus and two of Oligoryctes, as well as many partial skulls, mandibles, and teeth of these and other taxa. Several of the new Apternodus specimens are also associated with postcrania. We recognize seven species of Apternodus, three of which are new, formally propose the combination Oligoryctes altitalonidus, and recognize two other genera of small, North American, anatomically zalambdodont placentals, Parapternodus and Koniaryctes. We regard two other taxa previously associated with North American fossil zalambdodonts, one Bridgerian and the other Tiffanian, as valid but do not name them in this paper. In addition, we argue that dental zalambdodonty entails a primary occlusal relationship between the paracone and the ectoflexid, and the reduction or absence of the metacone and talonid basin. A phylogenetic analysis of cranial, dental, and postcranial characters of 30 fossil and Recent taxa leads us to conclude that (1) the Apternodontidae as defined in previous literature is not monophyletic and should be restricted to seven species of Apternodus, (2) the genus Oligoryctes contains at least two species and has a considerably longer geologic record than Apternodus, (3) neither Micropternodus nor currently known Paleocene taxa are closely related to Apternodus or Oligoryctes, and (4) a case can be made for a close relationship among modern soricids, Parapternodus, Koniaryctes, Oligoryctes and Apternodus to the exclusion of other insectivoran-grade taxa. With the use of ordered, multistate character transformations, Solenodon comprises the sister taxon to a soricid-fossil zalambdodont clade

    Assessing the representation of species included within the Canadian Living Planet Index

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    To effectively combat the biodiversity crisis, we need ambitious targets and reliable indicators to accurately track trends and measure conservation impact. In Canada, the Living Planet Index (LPI) has been adapted to produce a national indicator by both World Wildlife Fund-Canada (Canadian Living Planet Index; C-LPI) and Environment and Climate Change Canada (Canadian Species Index) to provide insight into the status of Canadian wildlife, by evaluating temporal trends in vertebrate population abundance. The indicator includes data for just over 50% of Canadian vertebrate species. To assess whether the current dataset is representative of the distribution of life history characteristics of Canadian wildlife, we analyzed the representation of species-specific biotic variables (i.e., body size, trophic level, lifespan) for vertebrates within the C-LPI compared to native vertebrates lacking LPI data. Generally, there was considerable overlap in the distribution of biotic variables for species in the C-LPI compared to native Canadian vertebrate species lacking LPI data. Nevertheless, some differences among distributions were found, driven in large part by discrepancy in the representation of fishes—where the C-LPI included larger-bodied and longer-lived species. We provide recommendations for targeted data collection and additional analyses to further strengthen the applicability, accuracy, and representativity of biodiversity indicators

    Influence of FK 506 (tacrolimus) on circulating CD4 <sup>+</sup> t cells expressing cd25 and cd45ra antigens in 19 patients with chronic progressive multiple sclerosis participating in an open label drug safety trial

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    We have taken the opportunity of a clinical trial of the potential efficacy and safety of FK 506 (tacrolimus) in chronic progressive multiple sclerosis (MS) to examine the influence of this potent new immunosuppressant on circulating T-lymphocytes in an otherwise healthy non-transplant population. Peripheral blood levels of subsets of CD4+ T lymphocytes expressing the activation molecule interleukin-2 receptor (p55 α chain; CD25) or the CD45RA isoform were determined sequentially in 19 patients that were treated continuously with oral FK 506 (starting dose 0.15 mg/kg/day) for 12 months. No significant change in the proportion of circulating CD25 + CD4+ cells was observed over the study period in which the mean trough plasma FK 506 level rose from 0.3 ±0.2 to 0.5 ±0.4 ng/ml. There was also no significant effect of FK 506 on the percentage of CD45RA + CD4 + cells in the peripheral blood at 12 months compared with pretreatment values. Analysis of a subgroup of 7 patients, who showed a sustained reduction in CD25 + CD4+ cells and a reciprocal increase in CD45RA* CD4 * cells for at least 6 months after start of treatment, did not reveal any difference in disability at one year compared with the treatment group as a whole. The side effects of FK 506 were mild and the overall degree of disability estimated by the mean Kurtzke expanded disability status scale (EDSS) score or the ambulation index did not deteriorate significantly in the 19 patients studied over the 12 months of FK 506 administration. © 1994 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted

    The Mantle Transition Zone Beneath West Antarctica: Seismic Evidence for Hydration and Thermal Upwellings

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    Although prior work suggests that a mantle plume is associated with Cenozoic rifting and volcanism in West Antarctica, the existence of a plume remains conjectural. Here we use P wave receiver functions (PRFs) from the Antarctic POLENET array to estimate mantle transition zone thickness, which is sensitive to temperature perturbations, throughout previously unstudied parts of West Antarctica. We obtain over 8000 high-quality PRFs using an iterative, time domain deconvolution method filtered with a Gaussian width of 0.5 and 1.0, corresponding to frequencies less than ∼0.24 and ∼0.48 Hz, respectively. Single-station and common conversion point stacks, migrated to depth using the AK135 velocity model, indicate that mantle transition zone thickness throughout most of West Antarctica does not differ significantly from the global average, except in two locations; one small region exhibits a vertically thinned (210 ± 15 km) transition zone beneath the Ruppert Coast of Marie Byrd Land and another laterally broader region shows slight, vertical thinning (225 ± 25 km) beneath the Bentley Subglacial Trench. We also observe the 520 discontinuity and a prominent negative peak above the mantle transition zone throughout much of West Antarctica. These results suggest that the mantle transition zone may be hotter than average in two places, possibly due to upwelling from the lower mantle, but not broadly across West Antarctica. Furthermore, we propose that the transition zone may be hydrated due to \u3e100 million years of subduction beneath the region during the early Mesozoic

    A new species of Argyromys (Rodentia, Mammalia) from the oligocene of the valley of lakes (Mongolia): its importance for palaeobiogeographical homogeneity across Mongolia, China and Kazakhstan

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    We describe a new species of Rodentia (Mammalia), Argyromys cicigei sp. nov. from Toglorhoi (fossil bed TGW-A/2a) in Mongolia and Ulantatal (fossil beds UTL 1 and UTL 7) in China. Its tooth morphology differs from the type species Argyromys aralensis from Akespe in Kazakhstan by smaller size and simpler structures. Argyromys has been assigned in different families of Muroidea, such as Tachyoryctoididae and Spalacidae. However, the presence of common characters indicates a closer relationship of Argyromys with the genera of Cricetidae s.l. (subfamilies Eucricetodontinae; Cricetopinae; Cricetodontinae and Gobicricetodontinae among others) from Asia than with the earliest representatives of Spalacidae or the endemic Tachyoryctoididae. Argyromys cicigei sp. nov. possesses a simple anterocone and anteroconid in the upper and lower first molars, respectively, which is characteristic for Cricetidae s.l. It has a flat occlusal surface in worn specimens; weakly-developed posterolophs; an oblique protolophule and metaloph on the upper molars and it lacks a labial anterolophid on the m1. These traits are also typical of the Oligocene genera Aralocricetodon and Plesiodipus, included in the subfamilies Cricetodontinae and Gobicricetodontinae respectively. The cladistic analysis performed here supports this hypothesis. The clade formed by Argyromys species is grouped with other cricetid taxa (s.l). Spalacids, however, form a different clade, as do the tachyoryctoids. Previous authors state that the Aral Formation (Kazakhstan) should be dated to the Oligocene instead of the Miocene, based on the presence of several taxa. The finds of Argyromys in both regions supports the statement that they are closer in age than previously thought. The occurrence of Argyromys in Kazakhstan, Mongolia and China evidences the biogeographic unity of the Central Asian bioprovince during the Oligocene

    Conservatism and adaptability during squirrel radiation : what is mandible shape telling us?

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    SYNTHESYS Project from the European Community Research Infrastructure (NL-TAF-4084)Both functional adaptation and phylogeny shape the morphology of taxa within clades. Herein we explore these two factors in an integrated way by analyzing shape and size variation in the mandible of extant squirrels using landmark-based geometric morphometrics in combination with a comparative phylogenetic analysis. Dietary specialization and locomotion were found to be reliable predictors of mandible shape, with the prediction by locomotion probably reflecting the underlying diet. In addition a weak but significant allometric effect could be demonstrated. Our results found a strong phylogenetic signal in the family as a whole as well as in the main clades, which is in agreement with the general notion of squirrels being a conservative group. This fact does not preclude functional explanations for mandible shape, but rather indicates that ancient adaptations kept a prominent role, with most genera having diverged little from their ancestral clade morphologies. Nevertheless, certain groups have evolved conspicuous adaptations that allow them to specialize on unique dietary resources. Such adaptations mostly occurred in the Callosciurinae and probably reflect their radiation into the numerous ecological niches of the tropical and subtropical forests of Southeastern Asia. Our dietary reconstruction for the oldest known fossil squirrels (Eocene, 36 million years ago) show a specialization on nuts and seeds, implying that the development from protrogomorphous to sciuromorphous skulls was not necessarily related to a change in diet

    A New Heteromyid Rodent From The Early Oligocene Of Natrona County Wyoming

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    Volume: 85Start Page: 179End Page: 19

    Sharamynodon (Mammalia : Perissodactyla) From The Eocene Of The Ily Basin, Kazakstan And The Antiquity Of Asian Amynodonts

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    Volume: 114Start Page: 517End Page: 52
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