Paul Bernier

Bio: Paul Bernier is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Sea level & Holocene. The author has an hindex of 9, co-authored 18 publications receiving 285 citations.

Constraints on the timescale of animal evolutionary history

Abstract: Dating the tree of life is a core endeavor in evolutionary biology. Rates of evolution are fundamental to nearly every evolutionary model and process. Rates need dates. There is much debate on the most appropriate and reasonable ways in which to date the tree of life, and recent work has highlighted some confusions and complexities that can be avoided. Whether phylogenetic trees are dated after they have been established, or as part of the process of tree finding, practitioners need to know which calibrations to use. We emphasize the importance of identifying crown (not stem) fossils, levels of confidence in their attribution to the crown, current chronostratigraphic precision, the primacy of the host geological formation and asymmetric confidence intervals. Here we present calibrations for 88 key nodes across the phylogeny of animals, ranging from the root of Metazoa to the last common ancestor of Homo sapiens. Close attention to detail is constantly required: for example, the classic bird-mammal date (base of crown Amniota) has often been given as 310-315 Ma; the 2014 international time scale indicates a minimum age of 318 Ma. Michael J. Benton. School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, U.K. mike.benton@bristol.ac.uk Philip C.J. Donoghue. School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, U.K. phil.donoghue@bristol.ac.uk Robert J. Asher, Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, U.K. r.asher@zoo.cam.ac.uk Matt Friedman, Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, U.K. mattf@earth.ox.ac.uk Thomas J. Near, Department of Ecology and Evolutionary Biology, Yale University, P. O. Box 208106, 165 Prospect Street, New Haven, CT 06520-8106, U.S.A. thomas.near@yale.edu Jakob Vinther. School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, U.K. jakob.vinther@bristol.ac.uk PE Article Number: 18.1.1FC Copyright: Society for Vertebrate Paleontology February 2015 Submission: 1 August 2013. Acceptance: 7 December 2014 Benton, Michael J., Donoghue, Philip C.J., Asher, Robert J., Friedman, Matt, Near, Thomas J., and Vinther, Jakob. 2015. Constraints on the timescale of animal evolutionary history. Palaeontologia Electronica 18.1.1FC; 1-106; palaeo-electronica.org/content/fc-1 Calibrations published in the Fossil Calibration Series are accessioned into the Fossil Calibration Database (www.fossilcalibrations.org). The Database is a dynamic tool for finding up-to-date calibrations, and calibration data will be updated and annotated as interpretations change. In contrast, the Fossil Calibration papers are a permanent published record of the information on which the calibrations were originally based. Please refer to the Database for the latest data. BENTON ET AL.: ANIMAL HISTORY TIMESCALE

A review of the reptile and amphibian assemblages from the Stormberg of southern Africa, with special emphasis on the footprints and the age of the Stormberg

Abstract: The Molteno, Elliot, and Clarens formations comprise the continental Stormberg Group of the Karoo Basin of South Africa and Lesotho. The Molteno Formation contains a well preserved macroand microfloral assemblage but apparently no vertebrates; the Elliot and Clarens formations contain abundant vertebrates but virtually no floral remains. The vertebrate taxa represented by skeletal remains are listed and divided into two assemblages the lower Stormberg (lower Elliot) and upper Stormberg (upper Elliot and Clarens) assemblages. The abundant, diagnosable footprint taxa are revised and their names reduced to eight genera. These ichnotaxa also fall into two biostratigraphic zones that parallel the skeletal assemblages. Comparison of the faunal assemblages with those of the European type section strongly suggests that the lower Stormberg assemblage is Late Triassic (CarnianNorian) in age while the upper Stormberg assemblage is Early Jurassic (Hettangian-Pliensbachian) in age. Comparisons with other continental assemblages from other areas suggest that the upper Stormberg (upper Elliot and Clarens formations) assemblage broadly correlates with the upper Newark Supergroup of eastern North America, the Glen Canyon of the southwestern United States, and the lower Lufeng Series of China all thought to be of Early Jurassic age on the basis of floral and/or radiometric evidence. Based on these correlations, previously published paleobiogeographic maps are revised; these show a shift from Late Triassic floral and faunal provinciality to Early Jurassic homogeneity. This shift was synchronous with a widening of the equatorial arid zone.

Causes and Emission of Luminescence in Calcite and Dolomite

Abstract: Luminescence in calcite and dolomite is governed by physical phenomena that are common to all oxygen-dominated crystalline substances, including other carbonates and silicates. Absorption of excitation energy, energy transfer, and emission involve predictable transitions between electronic energy levels. Strong emission in various colors is always caused by impurities which function as activators of luminescence. Visible luminescence is not expected from pure, undistorted insulators, including carbonates. However, a faint blue 'intrinsic' luminescence, with a broad emission peak (band) around 400 nm, presumably caused by lattice defects, occurs in pure calcite and dolomite, and even in some samples containing impurities. The most important activators in carbonates are transition elements and rare earth elements. Luminescence spectra can be used for activator identification. These spectra are largely independent of the type of excitation, e. g., electron beam (cathodoluminescence = CL), photon (photoluminescence = PL), X-Ray (radioluminescence = RL) excitation, and others. Emission intensities depend on activator, sensitizer, and quencher concentrations, and on the method of excitation. At a given activator concentration, the luminescence intensity generally increases with an increase in excitation energy from PL (relatively weak) to CL (strong). Changes in visual luminescence color between different excitation methods are caused by relative changes in emission peak heights. Mn2* appears to be the most abundant and important activator in natural calcite and dolomite. Substituting for calcium in both minerals, its emission is orange-red to orange-yellow, with a fairly broad band between 570-640 nm (maximum between 590-620 nm). The emission band maximum of Mn2* substituting for Mg2* (in dolomite) is located around 640-680 nm. As little as 10-20 ppm Mn2* in solid solution are sufficient to produce visually detectable luminescence, if total Fe contents are below about 150 ppm. Sm3* activated luminescence can be visually indistinguishable from that activated by Mn2*. The spectrum of Sm3* emission, however, is quite distinct from that of Mn2* and consists of three narrow bands at 562 nm, 604 nm, and 652 nm. Tb3+ and Dy3+ activate green and cream-white luminescence, respectively. The main emission of Tb3* is at 546 nm. The emission of Dy3t consists of three bands, located at 484 nm, 578 nm, and 670 nm. Emission from Eu-containing calcite is red or blue. Narrow spectral bands of 590 nm, 614 nm, and 656 nm are caused by Eu3* and correspond to the red emission. A broad emission spanning a large range of shorter wavelengths is caused by Eu2* and corresponds to the blue emission. As in the case of Sm3*-activated luminescence, the red Eu3* luminescence can be mistaken visually for Mn2*-activated luminescence. Visual luminescence detection limits for rare earths are on the order of 10 ppm. Pb2* is an activator, with an emission band around 480 nm, but it also is a sensitizer of Mn2*-activated luminescence in carbonates. Another recognized sensitizer for Mn2* in carbonates is Ce3*. Sensitizers appear to be effective at concentrations as low as 10 ppm in calcite. Quenchers of Mn2*-activated luminescence in carbonates are Fe2*, Co2*, Ni2*, and Fe3*. The concentrations at which quenchers appear to be effective may vary from element to element and with host mineralogy. Effective minimum concentrations as low as 30-35 ppm have been reported for calcite. The interplay of Mn2* and Fe2*, commonly regarded to be the most important activator and quencher, respectively, in determining the luminescence characteristics of natural carbonates is not well understood because the available data are partially inconsistent. The Mn/Fe ratio may exert a control on luminescence intensity. Mn and Fe concentrations at which 'bright' CL changes to 'dull' can be determined only semi-quantitatively. The available data on the concentration of Mn2* at which quenching starts are partially inconsistent Consequently, the Mn2* concentration at which concentration extinction occurs has not been determined unequivocally. The data presented and summarized in this paper can be used as a basis for the interpretation of luminescence of geological materials. Li particular, knowledge of the possibilities and complexities of activation, sensitization, and quenching has great potential for the interpretation of diagenetic carbonate cements.