ALBERT

Description: 〈span〉The planet Mercury is sufficiently close to the Sun to pose a major challenge to spacecraft exploration. The 〈span〉Mariner 10〈/span〉 spacecraft flew by Mercury three times in 1974–1975 but viewed less than half of the surface. With the three flybys of Mercury by the 〈span〉MESSENGER〈/span〉 spacecraft in 2008–2009 and the insertion of that probe into orbit about Mercury in 2011, our understanding of the innermost planet substantially improved. In its four years of orbital operations, 〈span〉MESSENGER〈/span〉 revealed a world more geologically complex and compositionally distinctive, with a more dynamic magnetosphere and more diverse exosphere–surface interactions, than expected. With the launch of the 〈span〉BepiColombo〈/span〉 dual-orbiter mission, the scientific understanding of the innermost planet has moved another major step forward.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉A new species of the Paleozoic bryozoan genus 〈span〉Ptilotrypa〈/span〉 of the order Cryptostomata is described from the lower part of the Yong Limestone Formation, Katian, Upper Ordovician of the Kumaun Tethys Himalaya: 〈span〉Ptilotrypa bajpaii〈/span〉 new species. The presence of the genus 〈span〉Ptilotrypa〈/span〉 in the Tethyan Himalaya suggests paleogeographic connections to the Upper Ordovician of North America and, consequently, Upper Ordovician age for the lower part of the Yong Limestone Formation. This species displays a reticulate colony shape, which suggests an efficient filtering capacity in an environment with a high primary production. Morphological peculiarities and systematic assignment of the genus 〈span〉Ptilotrypa〈/span〉 are discussed.UUID: http://zoobank.org/898276c8-2924-4da2-ae96-3392cb2ebbc3〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The Signor-Lipps effect states that even a sudden mass extinction will invariably appear gradual in the fossil record, due to incomplete fossil preservation. Most previous work on the Signor–Lipps effect has focused on testing whether taxa in a mass extinction went extinct simultaneously or gradually. However, many authors have proposed scenarios in which taxa went extinct in distinct pulses. Little methodology has been developed for quantifying characteristics of such pulsed extinction events. Here we introduce a method for estimating the number of pulses in a mass extinction, based on the positions of fossil occurrences in a stratigraphic section. Rather than using a hypothesis test and assuming simultaneous extinction as the default, we reframe the question by asking what number of pulses best explains the observed fossil record.Using a two-step algorithm, we are able to estimate not just the number of extinction pulses but also a confidence level or posterior probability for each possible number of pulses. In the first step, we find the maximum likelihood estimate for each possible number of pulses. In the second step, we calculate the Akaike information criterion and Bayesian information criterion weights for each possible number of pulses, and then apply a 〈span〉k〈/span〉-nearest neighbor classifier to these weights. This method gives us a vector of confidence levels for the number of extinction pulses—for instance, we might be 80% confident that there was a single extinction pulse, 15% confident that there were two pulses, and 5% confident that there were three pulses. Equivalently, we can state that we are 95% confident that the number of extinction pulses is one or two. Using simulation studies, we show that the method performs well in a variety of situations, although it has difficulty in the case of decreasing fossil recovery potential, and it is most effective for small numbers of pulses unless the sample size is large. We demonstrate the method using a data set of Late Cretaceous ammonites.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉In this contribution, four species of 〈span〉Agathoxylon〈/span〉 are described from the La Matilde Formation, Gran Bajo de San Julián and central and south-western sectors of Santa Cruz Province, Argentina. 〈span〉Agathoxylon agathioides〈/span〉 (Kräusel and Jain) n. comb., 〈span〉Agathoxylon santalense〈/span〉 (Sah and Jain) n. comb., 〈span〉Agathoxylon termieri〈/span〉 (Attims) Gnaedinger and Herbst, and the new species 〈span〉Agathoxylon santacruzense〈/span〉 n. sp. are described based on a detailed description of the secondary xylem. In this work, it was possible to construct scatter plots to elucidate the anatomical differences between the fossil species described on quantitative anatomical data. Comparisons are made with other 〈span〉Agathoxylon〈/span〉 species from Gondwana. These parameters can be used to discriminate genera and species of wood found in the same formation, as well as to establish differences/similarities between other taxa described in other formations. Some localities contain innumerable “in situ” petrified trees, which allowed us to infer that these taxa formed small forests, or local forests, or small forests within a dense forest, which is a habitat coincident with the extant Araucariaceae.〈/span〉