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Milwaukee, WI, United States

Adults of two species of cicadas, Proarna sallei Stål, 1864 and Pacarina championi (Distant, 1881) (Hemiptera: Cicadidae), were observed and counted at a cluster of three electric lights on the wall of a cacao storage building at La Lola. La Lola is an experimental cocoa farm, near Matina, Costa Rica, Central America. Observations were taken intermittently from 1980 to 1986. All individuals at the lights for both species were females. Of the total 19 individuals of Pa. championi counted, 94.7% occurred during the wetter periods. Eighty-eight percent of the 25 Pr. sallei individuals occurred during the wetter periods. Although not as biased as the Costa Rican site, females made up 70% of the total 530 specimens of Pr. insignis Distant, 1881 collected at various types of light traps in the Department of French Guiana, South America. Similar female bias is also reported for Pr. grisea (Fabricius, 1775) and Pr. guttulosa (Walker, 1858) also collected in South America. Previous studies show the sex ratio of Proarna and other genera of cicadas in Costa Rica is 1:1 at adult eclosion. The data are discussed in terms of possible behavioral differences between the sexes in the attraction to lights. © New York Entomological Society.

Jin J.,University of Western Ontario | Harper D.A.T.,Durham University | Cocks L.R.M.,Natural History Museum in London | McCausland P.J.A.,University of Western Ontario | And 2 more authors.
Geology | Year: 2013

The Late Ordovician equatorial zone, like the zone today, had few hurricane-grade storms within 10o of the equator, as emphasized by the preservation of massive-bedded Thalassinoides ichnofacies in a trans-Laurentian belt more than 6000 km long, from the southwestern United States to North Greenland. That belt also includes nonamalgamated shell beds dominated by the brachiopod Proconchidium, which would not have been preserved after hurricane-grade storms. The belt lacks such storm-related sedimentary features as rip-up clasts, hummocky cross-stratification, or large channels. In contrast, other contemporaneous Laurentian Thalassinoides facies and shell beds on either side of the belt have been disturbed by severe storms below fair-weather wave base. The position of the biofacies-defined equatorial belt coincides with the Late Ordovician equator deduced from paleomagnetic data from Laurentia, thus providing both a high-precision equatorial location and an independent test of the geocentric axial dipole hypothesis for that time. © 2013 Geological Society of America.

McGhee Jr. G.R.,Rutgers University | Sheehan P.M.,Milwaukee Public Museum | Bottjer D.J.,University of Southern California | Droser M.L.,University of California at Riverside
Geology | Year: 2012

We propose a new ecological ranking of the major Phanerozoic biodiversity crises in which the Serpukhovian biodiversity crisis is ranked fifth in ecological impact, lesser than the Late Devonian but greater than the end-Ordovician, and the end-Ordovician mass extinction is ranked sixth. It is interesting that both the end-Ordovician mass extinction and the Serpukhovian biodiversity crisis were triggered by glaciations. Other than that common trigger, the two events were very different. Glaciation in the Ordovician triggered an enormous jump in the extinction rate of marine organisms and was taxonomically very severe, yet the ecological impact of those extinctions was minimal. Glaciation in the Serpukhovian triggered a precipitous drop in the speciation rate but only moderate diversity losses, yet the ecological impact of those diversity losses and ecosystem restructuring was an ecological level of magnitude larger than that seen in the end-Ordovician mass extinction. © 2012 Geological Society of America.

Robertson D.S.,University of Colorado at Boulder | Lewis W.M.,University of Colorado at Boulder | Sheehan P.M.,Milwaukee Public Museum | Toon O.B.,University of Colorado at Boulder
Journal of Geophysical Research: Biogeosciences | Year: 2013

The global debris layer created by the end-Cretaceous impact at Chicxulub contained enough soot to indicate that the entire terrestrial biosphere had burned. Preliminary modeling showed that the reentry of ejecta would have caused a global infrared (IR) pulse sufficient to ignite global fires within a few hours of the Chicxulub impact. This heat pulse and subsequent fires explain the terrestrial survival patterns in the earliest Paleocene, because all the surviving species were plausibly able to take shelter from heat and fire underground or in water. However, new models of the global IR heat pulse as well as the absence of charcoal and the presence of noncharred organic matter have been said to be inconsistent with the idea of global fires that could have caused the extinctions. It was suggested that the soot in the debris layer originated from the impact site itself because the morphology of the soot, the chain length of polycyclic aromatic hydrocarbons, and the presence of carbon cenospheres were said to be inconsistent with burning the terrestrial biosphere. These assertions either are incorrect or have alternate explanations that are consistent with global firestorms. We show that the apparent charcoal depletion in the Cretaceous-Paleogene layer has been misinterpreted due to the failure to correct properly for sediment deposition rates. We also show that the mass of soot potentially released from the impact site is far too low to supply the observed soot. However, global firestorms are consistent with both data and physical modeling. Key Points A global heat pulse and fires from Chicxulub ejecta caused the K-Pg extinctionThis idea is consistent with all extant K-Pg data and physical modelingRecent claims of contrary evidence are either false or can be reinterpreted ©2013. American Geophysical Union. All Rights Reserved.

Harper D.A.T.,Statens Naturhistoriske Museum Geologisk Museum | Li J.,CAS Nanjing Institute of Geology and Palaeontology | Munnecke A.,GeoZentrum Nordbayern | Owen A.W.,University of Glasgow | And 2 more authors.
Episodes | Year: 2011

IGCP 503 'Ordovician Palaeogeography and Palaeoclimaté was established in 2004 primarily to identify the main drivers, both biological and geological, of the Great Ordovician Biodiversification Event. From the outset of the project it was clear that this event was part of a larger-scale, long-term, multifaceted process that included the end Ordovician extinction and Silurian recovery, if not more. IGCP 503 thus developed a major network that included scientists whose interests spanned the entire Lower Palaeozoic and encompassed a range of disciplines from classical palaeontology and palaeoecology through isotope geochemistry to climate modelling.

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