Ben Creisler
Some recent non-dino papers:
Free pdf:
Marc E. H. Jones, Peter W. Lucas, Abigail S. Tucker, Amy P. Watson, Joseph J. W. Sertich, John R. Foster, Ruth Williams, Ulf Garbe, Joseph J. Bevitt, Floriana Salvemini (2018)
Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile.
Journal of the Royal Society Interface 15: 20180039
DOI: 10.1098/rsif.2018.0039
Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement, making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15â0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08â0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity.
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Measuring the teeth of an ancient reptile (Eilenodon)
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Electrorana limoae gen. & sp. nov
Lida Xing, Edward L. Stanley, Ming Bai & David C. BlackburnÂ
The earliest direct evidence of frogs in wet tropical forests from Cretaceous Burmese amber.
Scientific Reports 8, Article number: 8770 (2018)Â
Frogs are a familiar and diverse component of tropical forests around the world. Yet there is little direct evidence from the fossil record for the antiquity of this association. We describe four fossil frog specimens from mid-Cretaceous (~99 mya) amber deposits from Kachin State, Myanmar for which the associated fauna provides rich paleoenvironmental context. Microcomputed tomographic analysis provides detailed three-dimensional anatomy for these small frogs, which is generally unavailable for articulated anurans in the Mesozoic. These crown-group anuran specimens provide the earliest direct evidence for anurans in a wet tropical forest. Based on a distinct combination of skeletal characters, at least one specimen has clear similarities to living alytoid frogs as well as several Mesozoic taxa known from the Jehol Biota in China. Whereas many Mesozoic frogs are from seasonal and mesic paleoenvironments, these fossils provide the earliest direct evidence of anurans in wet tropical forests.
News:
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Felipe Mendes S. Cardia, Rodrigo Miloni Santucc, Josà Vicente Elias Bernardi, Marco Brandalise de Andrade & Carlos Eduardo Maia de Oliveira (2018)
Mercury concentrations in terrestrial fossil vertebrates from the Bauru Group (Upper Cretaceous), Brazil and implications for vertebrate paleontology.
Journal of South American Earth Sciences (advance online publication)
Highlights
Fossils of Baurusuchidae present relatively high quantities of natural Hg.
Adult Baurusuchidae have about 30% more Hg than juvenile ones.
Volcanic activities and igneous rocks provided the Hg found in fossils.
Abstract
In this study we determined total mercury concentrations (THg) in a set of fossils from the Upper Cretaceous Bauru Group, Brazil, and investigated how the incorporation of this element occurs in fossil organisms and in their paleoenvironment. The analyzed fossil specimens were collected from two different locations (Jales and FernandÃpolis) of the Adamantina Formation and correspond to samples of teeth, bones, osteoderms, and crocodylomorph eggs (probably laid by Baurusuchidae), and their associated sediments. The samples were submitted to Zeeman atomic absorption spectrometry, showing concentrations ranging from approximately 5ângâgâ1 to 77ângâgâ1 in biomineral matrix. The results show mild fluctuations of Hg concentration in the different types of fossils analyzed, with teeth and bones retrieving more Hg than osteoderms, thus being the most suitable for this type of analysis. Adult specimens of Baurusuchidae showed ~30% more Hg than juvenile ones in their biomineralized tissues, which points to a continuous process of Hg accumulation throughout the individual's life history. As for the determination of Hg in sedimentary rocks, which has been previously claimed to be an indication of the relationship between volcanic activities and some mass mortality events (MMEs), the analysis of Hg in fossils can furnish additional information for future studies regarding the relationship between disturbances in the Hg cycle triggered by volcanic emissions and MMEs. Additionally, the results also suggest that the concentration of Hg in fossil vertebrates can be used as a tool for discussions about ontogenetic stages and, in some very particular cases, identification of female individuals.
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Free pdf:
I. Canales-Garcia, Urrutia-Fucugauchi & E. Aguayo-Camargo (2018)
Seismic imaging of Chicxulub Crater central sector, Yucatan Platform, Gulf of Mexico.
Geologica Acta 16(2): 215-235
DOI: 10.1344/GeologicaActa2018.16.2.6
Chicxulub crater, formed ~66Ma ago by an asteroid impact on the southern Gulf of Mexico, is the best preserved of the three large multi-ring basins in the terrestrial record. The crater structure is characterized by a semi-circular concentric ring pattern, marking the crater basin, peak ring, terrace zone and basement uplift. Analysis of a grid of 19 seismic reflection profiles using seismic attributes, marker horizons, contour surfaces and 3-D views is used to investigate the stratigraphy of the central zone. We used interactive software and routine applications to map the impact breccias, breccia-carbonate contact and post-impact carbonates. Four horizons marked by high-amplitude reflectors representing high impedance contrasts were identified and laterally correlated in the seismic images. Complex trace attribute analysis was applied for petrophysical characterization. Surface contour maps of base and top of stratigraphic packages were constructed, which mapped the impactites and post- and pre-impact carbonate stratigraphy. Basin floor, marked by the contact between the impact breccias and overlying carbonates is shown by laterally discontinuous high-amplitude reflectors. Discontinuous scattered reflectors interpreted as the upper breccias beneath the crater floor, have an average thickness of ~300msm. The Paleogene sedimentary units are characterized by multiple reflectors with lateral continuity, which contrast with the seismic response of underlying breccias. The basal Paleocene sediments follow the basin floor relief. Upwards in the section, the carbonate strata are characterized by horizontal reflectors, which are interrupted by a regional unconformity. Onlap/downlap packages over the unconformity record a period of sea level change.