Paleontology

Late Ordovician cooling event: Evidence from the Siberian cratonAuthor:1. Andrei Dronov (a)Affiliation:a. Geological Institute, Russian Academy of Sciences, Pyzhevsky per.7, 119017, Moscow, RussiaAbstract:The Upper Ordovician of the Tungus basin on the Siberian platform is represented by cool-water carbonates. Onset of cool-water conditions starts at the Darriwilian, and it is associated with widespread phosphatization, especially in the Volginian, Kirensko-Kudrinian and Chertovskian regional stages (mid-Darriwilian–lower Sandbian). The shift from tropical-type to temperate-type carbonates was preceded by destruction of the warm-water “carbonate factory” and a large input of siliciclastic material (Baykit Sandstone) during the Vikhorevian and Mukteian Regional Stages (lower to mid-Darriwilian). Wide distribution of temperate-type carbonates across the Siberian platform, located in the low latitudes in Ordovician time, can be explained by upwelling of cold oceanic waters and their penetration into epicontinental seas. The same situation was recorded for the Upper Ordovician of the North American platform. Newly discovered K-bentonite beds in the uppermost Sandbian – Katian of the Tungus basin are also associated with cool-water carbonates. The K-bentonite beds point to extensive volcanism on or near the western (in present-day orientation) margin of the Siberian craton in Late Ordovician time. Timing of the volcanism is surprisingly close to the period of volcanic activity of the Taconic arc near the margin of Laurentia. Both upwelling and volcanism seem to be activated by the same plate-tectonic reorganization, and both these processes seem to play an important role in a global, later Ordovician cooling terminated by the Hirnantian glaciation.

Just a quick one this week, as I'm busy preparing for the International Conference of Arachnology in Taipei next week. The wonderful assembly in the photograph above (by B. Frank) is a congregation of the Asian tramp snail Bradybaena similaris. The Bradybaenidae are a family of small snails, closely related to the garden snails of the Helicidae, that are mostly native to eastern Asia. However, a few species such as B. similaris have become widespread around the world as a result of human transportation. Not deliberate transportation of the snails themselves, of course, but transportation of plants and plant matter that have had the snails clinging to them. Also, recent phylogenetic studies have indicated that the Australasian snails hitherto included in the Camaenidae are in fact not close relatives of the North American representatives of that family, but should be placed close to or even within the Bradybaenidae (Wade et al. 2007). Euhadra grata gratoides, from here. You may already be familiar with the production by some species of snail of 'love darts', small calcareous spears that a mating snail fires into its partner. The function of the love dart is still not entirely understood, though it does seem to improve sperm uptake by the snail being darted: whether by lowering its ability to resist insemination, or because snails are mini-masochists that get off on being stabbed, I couldn't say. Most textbooks describing the use of love darts will (at least effectively) base their description on the common garden snail Cornu aspersum (or Cantareus aspersus, or whatever the heck we're supposed to be calling it these days), which leaves its love dart embedded in its partner's skin. Bradybaenids whose mating behaviour has been studied, however, do things a bit differently. Instead of abandoning its dart after a single firing, bradybaenids withdraw the dart and use it to stab their partner repeatedly, making it more of a love shiv than a love dart. And when I say repeatedly, I mean repeatedly: mating pairs of Euhadra subnimbosa would, on average, stab each other with the dart over 3300 times (Koene & Chiba 2006). So vigorous is the stabbing, in fact, that the dart pierces straight through the recipient and emerges through its foot! For those with JSTOR access, a video of the process can be seen at http://www.jstor.org/stable/10.1086/508028. And trust you to go rushing to watch a film of gastropod SM. REFERENCES Koene, J. M., & S. Chiba. 2006. The way of the samurai snail. American Naturalist 168 (4): 553-555. Wade, C. M., C. Hudelot, A. Davision, F. Naggs & P. B. Mordan. 2007. Molecular phylogeny of the helicoid land snails (Pulmonata: Stylommatophora: Helicoidea), with special emphasis on the Camaenidae. Journal of Molluscan Studies 73: 411-415.

As the closest planet to Earth, Venus is a relatively easy object to observe. However, many mysteries remain, not least the super-rotation of Venus' atmosphere, which enables high altitude winds to circle the planet in only four days. Now images of cloud features sent back by ESA's Venus Express orbiter have revealed that these remarkably rapid winds are becoming even faster.

The drift history of Adria and Africa from 280 Ma to Present, Jurassic true polar wander, and zonal climate control on Tethyan sedimentary faciesAuthors:1. G. Muttoni (a, b)2. E. Dallanave (c)3. J.E.T. Channell (d)Affiliations:a. Dipartimento di Scienze della Terra "A. Desio", Università degli Studi di Milano, via Mangiagalli 34, 20133 Milano, Italyb. ALP - Alpine Laboratory of Paleomagnetism, via Madonna dei Boschi 76, I-12016 Peveragno (CN), Italyc. Department of Earth and Environmental Science, Ludwig-Maximilians University, Munich D-80333, Germanyd. Department of Geological Sciences, University of Florida, Gainesville, FL 32611, USAAbstract:The orogenic belts surrounding the undeformed Adriatic Sea represent the margins of an area known as Adria, the African promontory. We have undertaken a critical appraisal of paleomagnetic data from regions of Adria considered parautochthonous relative to Africa and obtained either from biostratigraphically dated sedimentary rocks, corrected for inclination shallowing, or from igneous rocks that are regarded as free from any inclination shallowing bias. Paleomagnetic directions were used to calculate paleomagnetic poles for comparison with coeval, and inclination flattening-free, paleomagnetic poles from stable Africa. Visual coherence of paleopoles for several time slices from the Early Permian to the Eocene supports the construction of a composite apparent polar wander path (APWP) valid for parautochthonous Adria and stable Africa. This composite APWP is compared to previous APWPs, finding good agreement with the global APWP of Kent and Irving (2010). Both APWPs show a remarkable and rapid polar shift of ~ 40° in the Jurassic that other APWPs tend to underestimate. We interpret this shift to represent a major episode of true polar wander (TPW), from ~ 183 Ma in the Early Jurassic to ~ 151 Ma in the Late Jurassic. Using a simple zonal climate model, the drift motion of Adria attached to Africa appears to be consistent with the distribution of Permian–Cretaceous sedimentary facies on Adria.

3D printing can now be used to print lithium-ion microbatteries the size of a grain of sand. The printed microbatteries could supply electricity to tiny devices in fields from medicine to communications, including many that have lingered on lab benches for lack of a battery small enough to fit the device, yet provide enough stored energy to power them.To make the microbatteries, a team based at Harvard University and the University of Illinois at Urbana-Champaign printed precisely interlaced stacks of tiny battery electrodes, each less than the width of a human hair."Not only did we demonstrate for the first time that we can 3D-print a battery, we demonstrated it in the most rigorous way," said Jennifer Lewis, Ph.D., senior author of the study, who is also the Hansjörg Wyss Professor of Biologically Inspired Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), and a Core Faculty Member of the Wyss Institute for Biologically Inspired Engineering at Harvard University. Lewis led the project in her prior position at the University of Illinois at Urbana-Champaign, in collaboration with co-author Shen Dillon, an Assistant Professor of Materials Science and Engineering there.The results will be published online on June 18 in the journal Advanced Materials.

Over the past few weeks, Jacob and I were out doing some scouting and excavation in the lower Niobrara chalk in western Kansas. With the recent drought in the area, not much erosion has happened and so specimens were a bit tough to come by. Though we were blessed with instructions to just record fish localities, secure them, and move on, sometimes the fish are just too good to pass up.Enchodus palatine fang eroding outOne of our long term goals is to expand our 3 dimensional fish reproductions from Kansas. We've completed 4 so far (Xiphactinus, Ichthyodectes, Saurodon, Pachyrhizodus) and we're working on Megalocoelacanthus as our 5th. Enchodus has always been on our wish list (one of the most common fish in the WIS, and those fangs... people love pointy parts), however the large specimens of Enchodus petrosus are very rare, especially anything resembling a complete skeleton and not just isolated palatine bones with fangs.RMDRC 13-001 fanf after prepJacob struck first with a very large Enchodus fang protruding from the grey chalk between MU 7 and 8 He took down the overburden and exposed a sizable disarticulated skull with pectoral fins and vertebrae. We prepared a good portion of it in the lab and have decided that this specimen is where we will mold the majority of the individual elements from.RMDRC 13-001 digsiteA few days later I was working an outcrop slightly lower (just above MU 6) and was shocked to find an articulated skull weathering out of some seriously soft chalk. I hoped it was attached to the rest of an Enchodus.RMDRC 13-005 as foundOriginally we were going to "Sternberg" the specimen (pouring plaster directly over the exposed bones to stabilize everything in the jacket) assuming that there was more resent at the site. Unfortunately, sometimes all you get is a head. In this case a giant one (lower jaw 25cm long) indicating an overall length of about 1.25m. This will be the basis for our overall reconstruction.RMDRC 13-005, bottom side preparedWe're hoping for the prototype to be completed and ready for SVP at the end of October. Fingers crossed.

Trophic cascade alters ecosystem carbon exchangeAuthors:1. Michael S. Strickland (a,b)2. Dror Hawlena (c)3. Aspen Reese (a,d)4. Mark A. Bradford (a)5. Oswald J. Schmitz (a)Affiliations:a. School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511b. Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061c. Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Givat-Ram, Jerusalem 91904, Israeld. Department of Biology, Duke University, Durham, NC 27708Abstract:Trophic cascades—the indirect effects of carnivores on plants mediated by herbivores—are common across ecosystems, but their influence on biogeochemical cycles, particularly the terrestrial carbon cycle, are largely unexplored. Here, using a 13C pulse-chase experiment, we demonstrate how trophic structure influences ecosystem carbon dynamics in a meadow system. By manipulating the presence of herbivores and predators, we show that even without an initial change in total plant or herbivore biomass, the cascading effects of predators in this system begin to affect carbon cycling through enhanced carbon fixation by plants. Prolonged cascading effects on plant biomass lead to slowing of carbon loss via ecosystem respiration and reallocation of carbon among plant aboveground and belowground tissues. Consequently, up to 1.4-fold more carbon is retained in plant biomass when carnivores are present compared with when they are absent, owing primarily to greater carbon storage in grass and belowground plant biomass driven largely by predator nonconsumptive (fear) effects on herbivores. Our data highlight the influence that the mere presence of predators, as opposed to direct consumption of herbivores, can have on carbon uptake, allocation, and retention in terrestrial ecosystems.

I recently came across some photos that Ewan had emailed me a long time ago from our Smithsonian visit last fall, from the Garber oversize facility in Maryland. This was my first time seeing a skeleton of a southern sea lion (Otaria byronia). Unfortunately, I didn't get much time to check out the skeleton of this or any other modern pinnipeds, as my offsite visits were focused on fossil and modern mysticetes relating to my Ph.D. research. Another first: the totally bizarre skull of the Ganges river dolphin (Platanista gangetica) from Indo-Pakistan. One of the few odontocetes with obvious heterodonty, and with strange bony crests on either side of the face (part of the maxilla) that extend dorsally and wrap around the lateral and dorsal sides of the melon; the function of this structure is still not entirely understood.