Saturday 31 March 2012

New Tetrapodomorph Fish from the Devonian of Nevada.

Tetrapods are four-limbed terrestrial Vertebrates, plus animals which can be shown to have descended from four-limbed terrestrial Vertebrates, such as snakes or whales. Tetrapodomorph is a term which is used to refer to Tetrapods plus those fossil fish more closely related to them than to Lungfish. A Tetrapodomorph Fish is therefore any Tetrapodomorph that is not actually a Tetrapod, an imprecise taxonomic definition (since such definitions should not rely on simply excluding groups for convenience) but a useful one. The term 'fish' has little taxonomic significance (contrary to what tends to appear in school textbooks) since at its most precise it simply means any Vertebrate which is not a Tetrapod.

The study of Tetrapodomorph Fish is therefore important to our understanding of the colonization of land by Vertebrates, generally considered one of the most important events in the history of life on Earth.

In a paper published in the journal PLoS One on 20 March 2012, Brian Swartz of the Department of Integrative Biology and Museum of Paleontology at the University of California, Berkeley, describes a new species of Tetrapodomorph Fish from the Middle Devonian Red Hill I Beds in the Simpson Park Mountains in Eureka County, Nevada.

Tinirau clackae. Top, photograph. Middle, interpretive drawing based upon photograph. Abreviations: ba.a, anal basal;, basal articulation of the basipterygoid process; Basb1, basibranchial #1; bas.f, basicranial fenestra; Ch, ceratohyal; Clth, cleithrum; Clv, clavicle; Co3, posterior coronoid; de.f, dentary fang; Dpt, dermopalatine; Enpt, entopterygoid; Ept, ectopterygoid; Exsc.l, lateral extrascapular; Exsc.m, median extrascapular; Fe, femur; fib, fibula; fib.p, posterior process of the fibula; gle, glenoid fossa; Gu, lateral gular; Hh, hypohyal; Hu, humerus; Hyo, hyomandibular;, hyomandibular articulation; Ic, intercentrum; Int, intermedium; It, intertemporal; Ju, jugal; La, lacrimal; Mk, Meckelian bone; mk.grv, Meckelian groove; Mx, maxilla; na.a, anterior naris; nc.c, notochordal canal; ns, neural spine; Op, operculum;, parietal pitline; Part, prearticular; pin.f, pineal foramen; Plv, pelvis; Pmx, premaxilla; Po, postorbital; Pop, preoperculum; Pp, postparietal; Pq, palatoquadrate; Psph, parasphenoid; Qj, quadratojugal; Quad, quadrate; R, radius; ra, radial; ra.a, anal radial; ra.c, caudal radial; Ri, rib; Sang, surangular; Sbm, submandibular; Sca, scale; Sco, scapulocoracoid; Spl, splenial; St, supratemporal; st.f, subtemporal fossa; So.p, posterior supraorbital; Sq, squamosal; Tab, tabular; Te.a/Ro.l, anterior tectal+lateral rostral; tib, tibia; U, ulna; ul, ulnare; Uh, urohyal; Vo, vomer. (l) or (r) refers to left or right when displaced from natural side. Scale bar 10 cm. Bottom, reconstruction. Known elements in black, theorized elements in grey. Swartz (2012).

Swartz names the new species as Tinirau clackae, after Tinirau, a fish-man from Polynesian legend and Jenny Clack, a palaeontologist at the University of Cambridge noted for her expertise on evolution of early Tetrapods. Conodont fossils from the same sediments place Tinirau clackae in the Klapperina disparilis biozone, i.e. in the Late Givetian Stage of the Middle Devonian, a little over 385 million years ago. The Red Hill I Beds comprise lakers of limestone and calcarious mudstones, and contain fossil Conularids (solitary corals) which are thought to have been exclusively marine in origin and trace fossils associated with near-shore environments.

Left, Devonian outcrops in Eureka County, black. Yellow star labeled UCMP V74080 marks the site where Tinirau clackae was discovered. Inset, position of Eureka County in Nevada. Right, stratigraphic column showing where Tinirau clackae (yellow stars) was found vertically and chronologically. Swartz (2012).

Tinirau clackae is described from six specimens originally excavated by a University of California, Berkeley team lead by Joseph Gregory in the 1970s. These were extracted from the limey matrix using washes of dilute acid, then washed under running water for a month and air dried. The material had previously been studied by a graduate student at Berkeley in the 1980s, but the results never published.

While Tinirau clackae does not appear to be a direct ancestor of modern Tetrapods, it does reveal quite a lot about the evolution of the group, since its unique set of features required a re-assessment of relationships within the group, with a number of implications, most notably that Eusthenopteron, often thought of as being close to the lineage from which Tetrapods descended, is probably more distantly related than previously thought.

Evolutionary relationships within the Tetrapodomorph Fish, as implied from the glenoid fossa (A) and pelvic limbs (B) of Tinirau clackae. Swartz (2012).

Friday 30 March 2012

NASA releases new Cassini images of Saturn's moons Enceladus, Janus and Dione.

Saturn has fifty-three named moons, of which thirteen are larger than 50 km in diameter, and seven large enough to have formed a roughly spherical shape due to their own mass. Another nine unnamed moons of Saturn have confirmed orbits; the exact number of moons orbiting the planet is hard to assess, since each of the billions of tiny particles that make up Saturn's rings could potentially be seen as a moon.

The 33 largest moons of Saturn, showing comparative size and the order in which they orbit. NASA/JPL.

The orbits of Saturn's moons.

The Cassini Probe has been orbiting Saturn since June 2004, sending back scientific data and images of the planet and its moons. This week NASA released new images of three of the moons, Enceladus, Janus and Dione sent back by Cassini in the last few days.

Enceladus is the sixth largest moon of Saturn, with a diameter of 500 km. It orbits at a distance of 238 000 km, within the planet's E ring. Enceladus is a geologically active body, on which volcanic activity was observed near its south pole by Cassini in 2005. The surface of Enceladus is made up of a number of distinct terrains, some thought to be less than 100 million years old.

Image of Enceladus from 111 809 km. Taken by the Cassini Probe on 27 March 2012, and received on Earth on 28 March.

Image of Enceladus from 232 197 km. Taken by the Cassini Probe on 27 March 2012, and received on Earth on 28 March.

Image of Enceladus from 48 759 km. Taken by the Cassini Probe on 27 March 2012, and received on Earth on 28 March.

Image of Enceladus from 31 881 km. Taken by the Cassini Probe on 27 March 2012, and received on Earth on 28 March.

Janus is a small irregularly shaped moon, roughly 203 × 185 × 152.6 km. It orbits Saturn at roughly 151 500 km, in an almost identical orbit to another moon, Epimetheus, which caused some confusion for astronomers trying to establish the orbital parameters of what they had assumed was a single moon. The surface of Janus is heavily cratered, with some craters exceeding 30 km in diameter. The moon has a low density, which combined with its irregular shape, leads some planetary scientists to conclude it is a rubble pile rather than a solid object.

Image of Janus taken by the Cassini Probe on 27 March 2012, and received on Earth on 28 March.

Image of Janus taken by the Cassini Probe on 27 March 2012, and received on Earth on 28 March.

Dione is the forth largest moon of Saturn, and the fifteenth largest moon in the Solar System (since it is bigger than all the known smaller moons combined, this is an important distinction, the fifteen largest moons really are a different class of object). Dione orbits Saturn at about 377 400 km. It is a spherical object with an icy, crater covered surface, though its high density suggests it has a large rocky core.

Image of Dione from 78 998 km. Taken by the Cassini Probe on 28 March 2012, and received on Earth on the same day.

Image of Dione from 80 171 km. Taken by the Cassini Probe on 28 March 2012, and received on Earth on the same day.

Image of Dione from 44 528 km. Taken by the Cassini Probe on 28 March 2012, and received on Earth on the same day.

Image of Dione from 44 028 km. Taken by the Cassini Probe on 28 March 2012, and received on Earth on the same day.

The atmosphere of WASP-24b.

WASP-24 is an F-type star in the constellation of Virgo, 1076 light years from Earth. It has an effective temperature of 6075 K, compared to 5778 K for our Sun, is 1.13 times as massive as the Sun and has 6.32 times the Sun's volume. In 2009 a Hot Jupiter type planet was discovered orbiting WASP-24 by the SuperWASP planetary survey. This planet, WASP-24b, orbits the star at a distance of 0.0359 AU (3.59% of the distance between the Earth and the Sun), completing one orbit every 56.2 hours and is 1.01 times as massive as Jupiter, with 11 times Jupiter's volume (it is much less dense than Jupiter because it is much hotter, due to the heat from the nearby star, and therefore occupies more volume).

WASP-24b, compared to the planets of our Solar System. The Visual Exoplanet Catalogue.

In a paper published in the online arXiv database at Cornell University Library on 27 March 2012, and accepted for publication in the journal Astronomy & Astrophysics, a team of scientists led by Alexis Smith of the Astrophysics Group at Keele University describe the results of a study of the atmosphere of WASP-24b, using the Spitzer Space Telescope and the CAHA 2.2-m telescope at Calar Alto, Spain, combined with data previously collected by the SuperWASP-N and WASPSouth telescopes, the Liverpool, Faulkes North and Faulkes South Telescopes, and the Nordic Optical Telescope.

Smith et al. analyzed data from occultations of WASP-24 by WASP-24b, that is to say times when the planet passed in front of the star, in order to determine how shining through the atmosphere of the planet altered light from the star. From this they were able to determine that the atmosphere of WASP is reasonably clear; whereas other Hot Jupiter type planets have been shown to have opaque clouds of titanium and vanadium oxides.

From this they deduct that WASP-24b lacks a thermal inversion, a cool layer above and bellow which the temperature rises. On planets such as Earth or Jupiter, where such inversions exist, gasses precipitate out as liquids (or sometimes solids) in this layer, forming clouds. On WASP-24b, however, this will never happen, liquids that evaporate here will never reach a cool layer in the atmosphere, and will not precipitate back out, either remaining as gasses in the atmosphere, or being lost into space.

Thursday 29 March 2012

Volcanic activity on Soufrière Hills, Montserrat.

Soufrière Hills is an active stratovolcano (singular, 'Hills' is part of the name; a single cone-shaped volcano with several summits) in the south of the island of Montserrat, in the Leeward Islands. The summit of the volcano rises 915 m above sea-level, and it has a 1 km wide crater, breached to the east by an eruption about 4000 years ago which caused a summit collapse.

On 22 Thursday March 2012 Soufrière Hills was struck by a swarms of Earthquakes between 4.00 and 5.00 pm. This was followed by a second, larger, Earthquake swarm between 3.00 and 5.30 on Friday 23 March. Later that day a new fumerole (gas emitting vent) was spotted on the northwest part of the volcano, and an ash plume rose 1.8 km above the volcano.

This is the first significant eruptive activity on Soufrière Hills in 2012, but is still considered to be part of the volcanic cycle which began in 1995, and which has caused a great deal of disruption on Montserrat, destroying the capitol, Plymouth, and causing the southern half of the island to be evacuated (mostly overseas).

The remains of Plymouth. June 2004. Montserrat Volcano Observatory.

Prior this there had been occasional (but rare) outbreaks of Earthquake activity on Soufrière Hills, but no significant eruption since about 1630.

The Leeward Islands are located at the eastern fringe of the Caribean Tectonic Plate. The Atlantic Plate is being subducted beneath this, and as it sinks into the Earth, is melted by the heat of the planets interior. Some of the melted material then rises up through the overlying Caribbean Plate as magma, fueling the volcanoes of the Leeward Islands and Windward Islands (together the Lesser Antilles Volcanic Arc).

The subduction of the Atlantic Plate beneath the Caribbean Plate fuels the volcanos of the Lesser Antilles Volcanic Arc. George Pararas-Carayannis.

Monday 26 March 2012

A fresh look at the Albian Ichthyosaur Platypterygius hercynicus.

The Ichthyosaurs were a group of marine tetrapods that resembled dolphins. They appear in the fossil record in the mid-Triassic about 245 million years ago, and survive till the mid-Cretaceous, about 90 million years ago. During the Jurassic they appear to have been the top marine predators, but in the Cretaceous they were overshadowed by other groups, most notably the Plesiousaurs. They are generally referred to as 'marine reptiles', but their relationship to other tetrapods is unclear, beyond the fact that they were clearly descended from terrestrial vertebrates. They bore live young, were fully aquatic, and may have been warm blooded, suggesting that they were as distinct from the Reptiles as Birds and Mammals are, and should probably just be called Ichthyosaurs.

Early Cretaceous Ichthyosaurs are not well understood, due to a small number of specimens, and the fragmentary nature of these specimens. One of these fragmentary specimens is a fragmentary Ichthyosaur skull found in the mid 1970s by amateur palaeontologist Jean−Pierre Debris at Saint−Jouin in the Seine−Maritime Department of northwestern France, and donated by him to the Muséum d’Histoire Naturelle du Havre.

Map of northern France, showing where Platypterygius hercynicus was originally discovered (star). Fischer (2012).

In a paper in the April 2012 edition of the journal Acta Palaeontologica Polonica, Valentin Fischer of the Geology Department at the University of Liège redescribes the Saint−Jouin Ichthyosaur, and uses it to draw conclusions about the classification of Early Cretaceous European Ichthyosaurs.

Fischer found that the Saint-Jouin specimen closely resembled the holotype (and only specimen of) Platypterygius hercynicus, and since in taxonomy a specimen is named as the holotype for each species, then any other specimen deemed to be similar enough belongs in the same species, the Saint-Jouin specimen was also allocated to the species Platypterygius hercynicus. Fischer also found individuals of the ammonite Callihoplites gr. strigosus in the rock-matrix in which the Ichthyosaur was preserved, dating the specimen to the Mortoniceras inflatum Zone or early Callihoplites auritus Subzone of the Albian age (the last subdivision of the Early Cretaceous), making it roughly 106.4 million years old.

The skull from Saint-Jouin newly assigned to Platypterygius hercynicus. Top, photograph. Middle, interpretive drawing. Bottom, reconstruction. Fischer (2012).

The new material is more extensive than the previous material assigned to Platypterygius hercynicus, allowing a better comparison to other members of the genus Platypterygius and other Ichthyosaurs within the Ophthalmosauridae, the group of Ichthyosaurs within which the genus Platypterygius is placed. Based upon this Fischer observes that some of the features originally assigned as definitive of the genus Platypterygius are not present in all the members of the genus, and that others are present in members of the Ophthalmosauridae not currently included within the genus. Based upon this he concludes that the genus Platypterygius as it currently stands is not a good taxonomic unit, and is in urgent need of revision.

The original German specimen of Platypterygius hercynicus from the late Aptian of Salzgitter. Right, photograph. Center, interpretative drawing by Kolb and Sander (2009). Left, new interpretative drawing, taking into account data from the Saint-Jouin specimen. Fischer (2012).

Chile struck by large Earthquake.

On Sunday 25 March 2012, slightly after 6.35 pm local time (slightly after 10.35 pm GMT), the central coast of Chile was struck by an Earthquake measured by the United States Geological Survey as 7.1 on the Richter Scale at a depth of 34.8 km, 27 km north of the city of Talca. This was felt along a stretch of coast measuring 77o km, including in the capitol, Santiago, 219 km to the north. At present only minor damage and injuries are being reported, but it is highly likely that more casualties will have occurred from a quake of this size.

Map showing the center of the quake, and the areas likely to have received the most intense shaking. USGS.

A tsunami warning was briefly issued by the Chilian Navey's Hydrographic and Oceanographic Service (SHOA), after police at Iloca and Duao reported seeing the sea withdraw sharply from the land, but this was called of shortly after, and an evacuation of low-lying coastal areas abandoned.

Chile is on the east coast of South America, where the Nazca Plate is being subducted beneath the South American Plate. As this happens the plates stick together then break apart as the pressure builds up, causing Earthquakes. This also leads to volcanic activity in the Andes Mountains, which run the length of Peru, as the Nazca Plate sinks into the Earth and is heated by the heat of the planet's interior, causing it to melt. Some of this melted material then rises through the overlying South American Plate as magma, fueling the Andean volcanoes.

Diagrammatic section through the Chile, showing how the subductive plate margin causes Earthquakes and volcanoes. Scripps Institution of Oceanography Survey of the Earthquake Zone off the Coast of Chile.

Sunday 25 March 2012

New species of Armored Catfish from Ecuador.

Armored Catfish, known in the aquaria trade as 'plecs' are freshwater Catfish from South America, noted for their sucker-like mouthparts and thick, armored scales. There are over 700 species, making them the largest group of Catfish, though the exact number of species is unclear, due both to a steady stream of new discoveries, and a series of taxonomic disputes about which species are valid.

In a paper published in the journal Zootaxa on 22 March 2012, Milton Tan and Jonathan Armbruster, both of the Department of Biological Sciences at Auburn University, describe a new species of Armored Catfish from the Río Santa Rosa in Ecuador.

The new species is named Cordylancistrus santarosensis, the Santa Rosa Armored Catfish. It is roughly 70 mm long, and distinguished by having armored plates on its snout, but not the flanks of its head; most closely related fish having either armored or unarmored heads. It is known from a single location on the Río Santa Rosa.

Cordylancistrus santarosensis. Tan & Armbruster (2012).

Map of the freshwater basins of northeast South America, showing the location where Cordylancistrus santarosensis was found. Tan & Armbruster (2012).

Understanding the subduction zone beneath Mexico.

The Middle American Trench, in which the Cocos Plate is subducted beneath the North American Plate, runs parallel to the south coast of Mexico. Like many subduction zones, this feeds a chain of volcanoes, the Trans-Mexican Volcanic Belt, as the subducting plate is melted by the heat of the Earth's interior and melts, some of the melted material then rising through the overlying plate as magma, feeding the volcanoes of the Volcanic Belt. However this Volcanic Belt runs parallel to neither the subduction zone nor the coast, but runs across Mexico at an angle, which requires an explanation.

The Trans-Mexican Volcanic Belt is at an angle to the Middle American Trench. Solleiro et al. (2007).

In a forthcoming paper in the Journal of Geophysical Research, Igor Stubailo, Caroline Beghein, Paul Davis, all of the Department of Earth and Space Sciences at the University of California Los Angeles, discuss a new three-dimensional model of the subduction zone beneath Mexico, based upon data from seismic monitoring stations across the country belonging to the Mesoamerican Seismic Experiment, the Network of Autonomously Recording Seismographs, the USArray, Mapping the Rivera Subduction Zone and the Mexican Servicio Sismologico Nacional.

The Cocos Plate is thought to have formed about 23 million years ago, when the Farallon Plate, an ancient tectonic plate underlying the East Pacific, split in two, forming the Cocos Plate to the north and the Nazca Plate to the south. Then, roughly 10 million years ago, the northwesternmost part of the Cocos Plate split of to form the Rivera Plate, south of Beja California.

The position of the Cocos, Nazca and Rivera Plates. MCEER/University at Buffalo.

The seismic monitoring stations were able to monitor not just Earthquakes in Mexico, but also Earthquakes in other parts of the world, monitoring the rate at which compression waves from these quakes moved through the rocks beneath Mexico, and how the structure of the rocks altered the movement of these waves.

Based upon the results from these monitoring stations, Stubailo et al. came to the conclusion that the Cocos Plate was split into two beneath Mexico, and that the two plates are subducting at different angles, one steep and one shallow. Since the rate at which a plate melts reflects its depth within the Earth, the steeper angled plate melts much closer to the subduction zone than the shallower angled plate, splitting the Trans-Mexican Volcanic Belt into sections above the different segments of the Cocos Plate, and causing it to apparently curve away from the subduction zone.

Top the new model of the Cocos Plate beneath Mexico, split into two sections (A & B) subducting at differing angles. (C) Represents the Rivera Plate, subducting at a steeper angle than either section of the Cocos Plate. The Split between the two has been named the Orozco Fracture Zone (OFZ) which is shown extended across the Cocos Plate; in theory this might in future split the Cocos Plate into two segments (though not on any human timescale). Bottom Left, the position of the segments on a map of Mexico. Darker area is the Trans-Mexican Volcanic Belt, orange circles are volcanoes, brown triangles are seismic monitoring stations, yellow stars are major cities. Bottom Right, an alternative model showing the subducting plate twisted but not split. This did not fit the data. Stubailo et al. (2012).

Saturday 24 March 2012

The Snail that eats Crabs.

Nactid Gastropods (Moonsnails) are predatory snails with a long fossil record. They typically predate smaller Gastropods and Bivalves, drilling through their prey's shells, then injecting digestive juices and sucking out the dissolved soft tissues if their victims. This leaves a distinctive boring, which is often used by palaeontologists to identify shells that have been attacked by Nactids.

A recent edition of the journal Molluscan Research contains a paper by Thomas Huelsken of the School of Biological Sciences at the the University of Queensland, describing how one species of Moonsnail, Conuber sordidus, native to Queensland, Australia, regularly attacks and eats Soldier Crabs, Mictyris longicarpus and Mictyris platycheles.

The snails attacked the crabs by fastening onto the back of their shells, the quickly enveloping and immobilizing them with they muscular feet. Once this was done the snails secreted mucus to cover the crab, then dragged it beneath the surface of the sediment to drill through its shell at leisure.

An attack on a Soldier Crab by a Moonsnail. (A) The snail seizes the crab from behind. (B) It envelopes the crab with its muscular foot, immobilizing it. (C) It secretes mucus, covering he crab, and making it harder for the crab to escape. (D) The crab is drawn beneath the sediment to be finished off at leisure. Huelsken (2012). A video of this feeding behavior has also been placed online.

The crabs, which feed when the tide is out, usually hide beneath the sediment when the tide is in. The were apparently induced to flee by the snails passing over them, when they were captured by the snails. Larger crabs were sometimes able to fight off the snails, but crabs 60% of the size of the snails or smaller were almost inevitably consumed. The snails were also seen to attack hermit crabs, though as they eat other snails it was unclear if they were deliberately targeting these.

Hermit Crab being consumed by a Moonsnail. Huelsken (2012).

Huelsken theorizes that this behavior may not be restricted to this species of Moonsnail, but may be widespread within the group. He also suggests the behavior may be precent in the fossil record. Crustacean shells with bore-holes are not uncommon fossil finds, but these are generally assumed to be the result of octopus attacks, as palaeontologists do not tend assume snails are capable of this sort of attack. Huelsken suggests that a review of drilled crustacean fossils in university and museum collections might reveal the presence of Nactid drillings previously identified as octopus drillings.

The Pleistocene Moonsnail Polonices heros (left), with clams showing signs of drilling attributed to a Nactid Gastropod from the same deposits. Maine Geological Survey.

Modern crab showing octopus drilling (top). Drilling is bottom left near the three large barnacles. Close up of drilling (bottom). Walla Walla University.

Soldier Crab remains with Nactid drilling. Scale bar is 5 mm. Huelsken (2012).

Friday 23 March 2012

Trying to find Peking Man.

Peking Man is a collective name given to a group of hominid fossils found at Zhoukoudian, near Beijing, between 1929 and 1937. This comprised remains from at least 15 individuals, assigned to the species Homo erectus, with an estimated age between 300 000 and 780 000 years old. In 1937 the invading Japanese army was drawing close to Zhoukoudian and the excavation was abandoned. The fossils were taken to the Peking Union Medical College, where in 1941 they were packed into crates in order to be evacuated to the United States. The plan was to ship the remains to the Fort Holcomb US Marine base near the port of Qinhaungdao, then ship them to America on board the SS President Harrison.

Reconstructed model of a Peking Man skull. University of Iowa.

Unfortunately the SS President Harrison was intercepted by a Japanese destroyer en route from Manila. The ship's master elected to scupper it by running it onto a small island, rather than allowing it to fall into enemy hands; the crew were captured, forced to work on refloating the ship, and eventually ended up in POW camps in Japan. Fort Holcomb and its Marine garrison were forced to surrender within a few weeks.

The Peking Man fossils are known to have left the Peking Union Medical College, but after that their fate is unknown. They never reached the U.S., but it is unclear if they ever reached Fort Holcomb, and they have not been seen since the war, generally being presumed to have been destroyed.

A paper in the March edition of the South African Journal of Science by Lee Berger of the Institute of Human Evolution at the University of the Witwatersrand and Wu Liu and Xiujie Wu of the Institute for Vertebrate Paleontology and Paleoanthropology in Beijing, discuss a report of a possible sighting of the Peking Man fossils in 1947, and its implications for the recovery of the specimens.

The sighting was reported by Paul Bowen who contacted Lee Berger in 2010, about a story he had been told by his father, Richard Bowen. Richard Bowen served as a Marine at Fort Holcomb in 1947, when the camp was briefly re-occupied by the US. During this time the site was surrounded by Chinese Communist troops, and it seemed highly likely that hostilities would commence. The Marines responded to this by digging a large number of fox-holes, and during the digging of one of these, apparently, came across a chest full of what appeared to be human remains, which the Marines found slightly distasteful and promptly reburied. Eventually the US garrisons in China were recalled to America without any fighting, where Mr Bowen eventually heard the story of the missing Peking Man fossils.

It seemed quite plausible that in the confusion of the 1941 siege of Fort Holcomb the chests were buried for later retrieval, but that nobody who knew where survived till the end of the war.

Mr Bowen senior was able to identify the approximate site where the chest was reburied in 1947, using old military maps and Google Earth, allowing the team to visit the site with a local historian. While the site had been re-developed, it was covered only by low-rise warehousing and parking lots, so there seems a reasonable chance that if the Peking Man remains were buried deep enough, they might have survived intact.

Top: 1938 military map of Fort Holcomb and the surrounding area. The arrow indicates the position of a railway bridge, and the box is the site of the enlisted men's barracks, close to which the box was buried. Bottom Google Earth map of the same area. Berger et al. (2012).

The area is due for re-developing in the near future, with larger buildings, which will require deeper foundations. Given the potential importance of the fossils the local Cultural Heritage Office have agreed to monitor the development closely, in the hope that Peking Man can be recovered.

Central Australia hit by major Earthquake.

At 7.55 pm on Friday 23 March 2012, local time (9.25 am GMT) a strong Earthquake shook the Ngarutjara Homeland in northern part South Australia, close to the border with the Northern Territory. The quake was measured as having a magnitude of 6.1 on the Richter Scale and a depth of 3 km by Geoscience Australia, and a magnitude of 5.6 on the Richer Scale at a depth of 10.7 km by the United States Geological Survey. Such an Earthquake could be potentially devastating in a densely populated area, but is not thought to have caused any serious damage or casualties, due to the low population and lack of high-rise buildings in the area where it hit. Locals are reported to be 'very concerned', however.

The location of the Ngarutjara Homeland Earthquake. USGS.

The cause of this Earthquake is not immediately clear. Central Australia is one of the least quake-prone places on the Earth; far less so than Western Europe or Eastern North America. The nearest plate boundaries run through New Zealand, Papua New Guinea and southern Indonesia, and these are boundaries with Oceanic, rather than continental plates, and therefore do not cause compression in the Australian continent (the major source of Earthquakes in Eurasia).

Thursday 22 March 2012

Skull shape and diet in an Ornithocheiroid Pterodactyl.

Istiodactylus latidens was first described in 1901 by Harry Govier Seely, under the name Ornithodesmus latidens, based upon material from the Early Cretaceous of southern England (this was changed after it was realized that the name Istiodactylus had already been assigned to a small Therapod Dinosaur). A reconstruction of the Pterodactyl was made by Reginald Hooley in 1913, which has served as the model for our understanding of the animal till the present; other reconstructions have been made in the intervening time, but all have essentially followed the pattern set by Hooley.

Reginald Hooley's 1913 interpretation of Istiodactylus latidens. Witton (2012).

This reconstruction of a weekly muscled, long snouted Pterodactyl with razor-like teeth has been hard to interpret. Three theories have been put forward, but none seems to completely fit with the available data. I has been suggested that Istiodactylus latidens could have been a dabbling filter-feeder, similar to a modern duck, a feeding technique that requires little strength, but ducks have short broad bills, whereas I. latidens has a long thin one, and no duck has razor sharp teeth. Alternatively I. latidens could have been a fish eater. Long thin shouts are good for catching fish, and do not necessarily need to be well muscled, but this hunting strategy normally requires pointed teeth, ideally curving backwards within the jaw, to catch and hold fish; razor blades would not be very useful, as they could hurt a fish, but not necessarily hold it. A third theory os that I. latidens could have been a carrion eater, as razor blade shaped teeth are good for cutting meat, but this requires a degree of physical strength that I. latidens apparently lacked.

In a paper published in the journal PLoS One on 21 March 2012, Mark Witton of the School of Earth and Environmental Sciences at the University of Portsmouth re-examines the original Istiodactylus latidens material to construct a new model of the skull, and is able to draw new conclusions about the animal's lifestyle from this.

Witton found that where Hooley had interpreted a gap in the centre part of the fossil as evidence for an elongate skull, the 'missing' piece of the skull was present; Hooley even described this, though he did not use it in his reconstruction. By reconstructing the skull with the missing piece in place, Witton came up with a shorter, stronger skull.

Istiodactylus latidens. (A-D) The fossil material. (E) Witton's reconstruction. Witton (2012).

Witton's shorter interpretation of the skull gives a stronger muscle attachment, at least for a shearing action. This strongly supports the carrion-feeding theory, as carrion feeders need to be able to cut through and ingest meat quickly (before anything else gets it) but do not need to deal with struggling prey, as with a carnivore. Witton also noted that Istiodactylus latidens lacked binocular vision, with eyes on the side of its head. This is strongly associated with carrion feeding in modern birds; carrion feeders need to be able to scan a lot of ground visually, but do not need to look for prey actively hiding or strike at prey trying to escape, both of which require good binocular vision. Based upon this Witton concludes that I. latidens was almost certainly a carrion feeder.

Reconstruction of Istiodactylus latidens as a carrion feeder. Witton (2012).

Wednesday 21 March 2012

Cooking the planets if CoRoT-7.

The CoRoT-7 stellar system was discovered in 2009 by the European Space Agency's COROT space probe. The system is roughly 489 light years away in the constellation of Monoceros, and comprises of a G-type star (CoRoT-7A)with 91% of the Sun's mass surrounded by at least two planets. The first of these, CoRoT-7b, orbits at a distance of 0.017 AU (i.e. 1.7% of the distance between the Earth and the Sun) every 20.5 hours and has a mass of about 7.4 times that of the Earth. The second planet, CoRoT-7c, orbits CoRoT-7A at a distance of 0.046 AU (4.6% of Earth's orbital distance) every 3.7 days and has a mass about 15 times that of the Earth. A possible third planet, CoRoT-7d, may orbit at 0.08 AU, and have a mass over 16 times that of the Earth's.

An artist's impression of CoRoT-7b. Catalano Fabien.

In a paper published on 19 March 2012 on the online arXiv database at Cornell University Library and accepted for publication in the journal Astronomy and Astrophysics, a team of scientists lead by Katja Poppenhaeger of the Hamburger Sternwarte, carry out an examination of the effects of being this close to the star on the planets of the CoRoT-7 system, based upon new observations by the European Space Agency's XMM Newton X-ray space telescope.

Poppenhaeger et al. calculate that CoRoT-7b is slowly being evaporated by the heat of it's star, losing 130 000 tonnes of mass every second. The CoRoT-7 system is thought to be about 1.5 billion years old, so if CoRoT-7b has not moved radically within the system during this time, and its composition has not changed greatly either, then it is likely to have lost between four and ten times the mass of the Earth during its history.

They also estimated that CoRoT-7c would be losing mass due to evaporation as well, but at roughly 10% of the rate for CoRoT-7B (i.e. about 13 000 tonnes of mass per second). However unlike CoRoT-7b, CoRoT-7c does transit the star, so that its radius and density cannot be calculated, making calculations on its makeup, and therefore how it will react to irradiation, highly speculative.

Tuesday 20 March 2012

Mexico shaken by major Earthquake.

Slightly after noon local time (slightly after 6 pm GMT) on Tuesday 20 March 2012 the southern Mexican coast was shaken by an Earthquake felt as far away as Mexico City. The quake was centered 15 km east of the city of Ometepec, (180 km west of Acapulco), at a depth of about 20 km, and measured 7.4 on the Richter Scale, according to the United States Geological Survey. Mexican authorities are reporting no casualties at this time, although it is highly likely that a quake of this time will have caused fatalities or serious injuries. Local media are reporting damage to hundreds of homes in the Ometepec area.

Map showing the extent and severity of shaking felt across southern Mexico. USGS.

South Mexico lies on the boundary between the Cocos and North American Plates. The Cocos Plate is being subducted beneath the North American Plate in the Middle America Trench, off the south coast of Mexico, and passing under Mexico as it sinks into the Earth. This is not a smooth process, the plates stick together while pressure builds up, then move in sudden jerks, causing Earthquakes. This subduction zone also fuels a number of volcanoes in Mexico and Central America, fed by material from the Cocos Plate that has been melted by the heat of the Earth's interior and risen up through the overlying North American and Caribbean Plates as liquid magma.

Mexico has suffered some severely damaging Earthquakes in the past. In 2003 a magnitude 7.6 quake centered on Colima killed 29 people and made over 10 000 homeless. In 1995 a magnitude 8.0 quake, also near Colima, killed about 50 people and made over a thousand homeless. In 1985 a magnitude 8.0 in the Michoacan Region killed at least 9500 people and made over 100 000 homeless.

United States Geological Survey releases a geological map of Io.

Io is the innermost of the four Galilean Moons of Jupiter; that is to say the moons discovered by Galileo Galilei in January 1610. It is also the most volcanically active body in the Solar System, with an estimated resurfacing rate of 10 mm per year, due to the tidal influences on the small moon by Jupiter and the larger moons Europa and Ganymede; there are no visible impact craters on the surface of Io.

The Io has been studied in detail by six NASA spacecraft, Voyager 1, Voyager 2, Hubble Space Telescope, Galileo, Cassini, and New Horizons, giving scientists a reasonable picture of the surface. In 2006 the United States Geological Survey released a set of four global mosaics of Io. These have now been updated, and combined with new data, to create a downloadable Geological Map of Io.

Detail of part of the new Map of Io. United States Geological Survey.