Thursday, 24 May 2012

Earthquake beneath the English Channel.

On Wednesday 23 May 2012, at slightly after 2.35 pm British Summertime (slightly after 1.35 pm GMT), an Earthquake was recorded by the British Geological Survey beneath the English Channel, roughly 70 km south of Eastbourne or 50 km west of Dieppe. The depth of the quake was unclear, but it was recorded as measuring 2.2 on the Richter Scale. The quake is unlikely to have been felt by anyone, much less to have caused any damage or casualties. Potentially a quake this size underwater could create a small tsunami, but nothing seems to have been observed in this instance.



The causes of Earthquakes in the English Channel are complex, being influenced by tectonic pressures from a number of sources. Europe is being pushed from the West by the expansion of the Atlantic and from the south by the northward movement of the African Plate. More locally there are lesser centers of expansion beneath the North Sea, the Rhine Valley and the Bay of Biscay, which excerpt pressure in the Channel Region. Finally there is glacial rebound; much of northern Europe was buried beneath hundreds of meters of ice till about 10 000 years ago. This pushed the rocks of the crust down into the lithosphere, and now the ice is gone the rocks are slowly rebounding.


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Velvet Geckos and Broad-headed Snakes; understanding the population structure of a favored prey item in order to help protect an endangered predator.

Broad-headed Snakes (Hoplocephalus bungaroides) are medium-sized (~60 cm) venomous snakes restricted to the Sydney Basin of New South Wales, Australia. Their numbers have declined greatly in recent years due to habitat loss and illegal collecting for the pet trade. Attempts to help the population of Broad-headed Snakes to recover have concentrated on the creation of artificial habitats to replace lost ones; in this case eroded sandstone outcrops that have been destroyed, sometimes illegally, by human activity.

A Broad-headed Snake (Hoplocephalus bungaroides) sheltering in an artificial rock crevice at Taronga Zoo. Zooinstitutes.

Snakes have been found to be willing to accept artificial rock-sites as suitable environments, and to be able to relocate themselves to new sites within about 10 km of existing colonies. However in order for populations to succeed, the snakes need not just a suitable environment to inhabit, but a source of suitable prey. 

Distribution map for the Broad-headed Snake (Hoplocephalus bungaroides). Australian Department of Sustainability, Environment, Water, Population and Communities.


Adult Broad-headed Snakes will happily consume a variety of prey animals, but the main food source for juveniles (~70% of all prey items) is the Velvet Gecko (Oedura lesueurii), which unlike the Snakes does not seem to willingly colonize new sites.

In a paper published in the journal BMC Evolutionary Biology on 14 May 2012, a team of scientists led by Sylvain Dubey of the Department of Ecology and Evolution at the University of Lausanne, detail the results of a study into the population of Velvet Geckos in order to assess how these animals disperse.

A Velvet Gecko (Oedura lesueurii). Ozanimals/Hexasoft.

Dubey et al. carried out two test on the Velvet Geckos. 

Firstly they tried a capture-tag-release-recapture experiment to find out how far individual Geckos naturally ranged. Despite running these tests for slightly over two and a half years they found that few of the Geckos travelled more than 30 m, and none of them was ever found to have moved more than 1.7 km from where it was originally captured.

Secondly they tried a genetic analysis of the populations of Velvet Geckos to see how much interbreeding was going on. This showed very little interbreeding between populations, with groups of Geckos separated by only a few kilometers apparently having been genetically isolated for millions of years. The Geckos have apparently remained at the colony sites constantly even through changing climate cycles.

This means that the Geckos are highly unlikely to colonize artificial sites on any useful sort of timescale, even it these sites are located on the sites of former colonies, and within easy reach of extant populations. It may still be possible, however, to artificially introduce the Geckos to sites, and establish new breeding colonies artificially. 


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Wednesday, 23 May 2012

The origin of domestic dogs.

Dogs are our oldest domestic animal, and the only one which predates the adoption of agriculture. This has led to a great deal of study of the origin of domestic dogs over the years. Despite this we are still not entirely sure where dogs were first domesticated. We are now confident that domestic dogs are descended from a single species of wild canid, the Grey Wolf (Canis lupus), and that domestic dogs were widespread across Eurasia by 12 000 years ago. The earliest dogs in the archaeological record are debatable; archaeological sites in Europe and Siberia contain several purported examples of domestic dogs dating back as far as 33 000 years ago, but it is hard to be confident that these were truly domesticated dogs and not just wolves foraging around human occupation sites. The widespread human habit of ritually burying dogs is generally taken as evidence of domestication; the oldest known ritual burial of a dog is from a site in the Czech Republic thought to be at least 26 000 years old. Attempts to date the domestication of dogs using molecular clocks (measuring the rate of DNA mutation and comparing it to the nearest known relative) have been inconclusive. One such study suggested dogs may have divered from wolves 135 000 years ago, but this is widely disputed.

Fossil dog skull from the Czech Republic, thought to be at least 26 000 years old. A mammoth bone has been placed in the dog's mouth, suggesting a ritual burial. Mietje Germonpré/Discovery News.

In a paper published in the Proceedings of the National Academy of Sciences on 21 May 2012, a team of scientists led by Greger Larson of the Department of Archaeology at the University of Durham publish the results of a new genetic study of the domestication of dogs, combined with a review of our current understanding of the subject.

The team studied the genetics of six dog breeds widely considered to be ancient, the Akita, the Basenj, the Eurasier, the Finnish Spitz, the Saluki and the Shar-Pei, and also looked at data from studies of ten other breeds considered ancient; the Afghan Hound, the Alaskan Malamute, the American Eskimo, the Canaan, the Chow Chow, the Dingo, the New Guinea Singing Dog, the Samoyed, the Shiba Inu and the Siberian Husky. 

Two of these dogs (the Eurasier and the American Eskimo are known to be twentieth century attempts to recreate ancient dogs; they should not show any notable differentiation from the general dog population. In the event the Eurasier did appear superficially to be ancient, but it is known to have been created by the hybridization of three ancient breeds, the Chow Chow, the Keeshond and the Samoyed, so this is not greatly surprising. 

The (African) Basenji, the Dingo and the New Guinea Singing Dog all originate from outside the range of the Grey Wolf, so these are highly unlikely to be ancient breeds, though they should show signs of long isolation from other breeds. In the event the Basenji did appear to be distinctive from other dogs, appearing ancient, whereas the Dingo and the New Guinea Singing Dogs appeared to have interbred with European dogs extensively in the recent past.

The Basenji; a dog breed from Central Africa which has largely escaped hybridization with European dogs. Dog Family.

The Alaskan Marmalute is the only other breed from outside Eurasia, being descended from ancient sled dogs used by Alaskan nomads, but this dog is known to have nearly become extinct in the twentieth century and been recreated by breeders. Unsurprisingly these did not appear to be ancient in the study.

The dogs that did appear to be ancient in origin were the Chinese Shar-Pei, the Japanese Akita, the Basenj, the North African Saluki, the Afghan Hound, the Eurasier and the Finnish Spitz. The Finnish Spitz is known to have nearly gone extinct in the 1880s, but to have been saved by the efforts of a breeder, Hugo Roos, who travelled to remote villages seeking out individuals that had not been hybridized with other dogs. All the other breeds are non-European, and appear to have had some degree of protection from hybridization with European dogs. None of them are from areas associated with ancient dog burials.

Interestingly several other Asian breeds, including the Tibetan Terrier and the Pekingese, appeared to be nearly as ancient, judged by their genetic isolation from other breeds. Larson et al. suggest that this may help to explain these results. Until the mid-nineteenth century European dog-breeders were little concerned with bloodline purity, so dogs from different breeds often hybridized. During this period Europeans expanded aggressively around the world, taking their dogs with them. Dogs are most likely to have first been domesticated in Europe or an adjacent area of Western Asia, but dogs from these areas have never been reproductively isolated. Genetic studies looking for 'ancient' breeds of dog are in fact looking for breeds that have been reproductively isolated for long periods of time, but the breeds this have achieved that are not particularly likely to be any closer to the original domestic dogs than those which have repeatedly hybridized with other breeds.

The Pekingese; not thought to be an ancient breed, but reproductively isolated for a long time. Dog Breed Info Center.


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Three new species of Tapir from the Early Eocene of Pakistan.

Tapirs are large tropical, forest dwelling, herbivorous mammals related to Horses and Rhinoceroses. They have an unusual distribution, being found in South and Central America, as well as in Southeast Asia. The oldest known Tapirs in the fossil record lived in North America during the early Eocene, around 55.4 million years ago. These early Tapirs are thought to have been essentially similar to modern Tapirs, though they probably lacked the small fleshy trunk that Tapirs have today. 

Skeleton of Heptodon, the oldest known Tapir, on display in the Harvard Museum of Natural History. Flo Bruehl/Geologic Resources.

In a paper published in the journal Acta Palaeontologica Polonica on 3 March 2012, Pieter Missiaen of the Department of Paleontology at the Royal Belgian Institute of Natural Sciences and Philip Gingerich of the Museum of Paleontology at the University of Michigan describe three new species of Tapirs from the Early Eocene Ghazij Formation of Pakistan. The fossils come from Ypresian deposits in the Gandhera Quarry in Balochistan, making them between 55.8 and 48.6 million years old. All are described from their teeth and jaws only.

Map showing the locations of Eocine deposits in Pakistan and neighboring areas of India. Missiaen & Gingerich (2012).

Two of the species are assigned to the new genus Gandheralophus, implying Tapir from Gandhera. These are named Gandheralophus minor and Gandheralophus robustus (small and solid respectively). G. robustus is roughly 15% larger than G. minor, but Missiaen & Gingerich consider them to be separate species rather than two sexes of the same species as both species show bi-modal distributions of tooth size; that is to say the teeth of each species fall into two groups based upon size within the group. 

Upper dentition of Gandheralophus minor (A-F) and G. robustus (G-K). Missiaen & Gingerich (2012).

Lower dentition of Gandheralophus minor (A-D) and G. robustus (E-I). Missiaen & Gingerich (2012).

The third new species is placed in the genus Litolophus, previously described from fossils discovered in Inner Mongolia. This is named Litolophus ghazijensis, for the Ghazij Formation. In addition a number of fragments from a fourth species were discovered, though this was not named.

Teeth from the unnamed Tapir from Gandhera (A & B), and Litolophus ghazijensis (C). Missiaen & Gingerich (2012).

All of these new finds show similarities to previously discovered fossils from East and Southeast Asia. This is interesting as fossils from other mammal groups previously studied from Gandhera and neighboring areas have shown closer affinities to European faunas.


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Tuesday, 22 May 2012

Earthquake in western Bulgaria.

On Tuesday 22 May 2012, sightly after 3.00 am local time (slightly after midnight GMT), western Bulgaria was shaken by an Earthquake centered on the village of Meshtitsa, 24 km west of the capitol, Sofia. The quake was recorded as measuring 5.6 on the Richter Scale at a depth of 9.4 km by the United States Geological Survey, and 5.8 on the Richter Scale at a depth of 10 km by the Bulgarian National Seismological Data Center. The quake was felt across western Bulgaria, including in Sophia, as well as in the neighboring states of Serbia, Macedonia, Romania and Greece. There are no reported casualties, but there was localized damage to houses, a widespread panic during the quake has been reported in the press. The area has been hit by a number of aftershocks, though none as large as the original quake.

Map showing the location of the 22 May 2012 quake. USGS.

The geology of the Balkan Peninsula is complex. Bulgaria lies on the Eurasian Plate, but it is surrounded by a number of microplates created by the collision of Africa with Europe from the south. Southern Greece lies on the Aegean Sea Plate, a breakaway part of the Eurasian Plate, which is being pushed to the southwest by the westward movement of the Anatolian Plate, another breakaway part of the Eurasian Plate underlying Turkey. This is in turn being pushed west by the northeasterly motion of the Arabian Plate, a breakaway part of the African Plate. The western part of the Balkan Peninsula, and the eastern part of Italy are underlain by the Adriatic (or Apulian) Plate, a breakaway part of the African Plate which has pushed like a wedge into southern Europe.

Map showing the movement of the microplates of the eastern Mediterranean. Kotzev et al. (1998).

Thus the rocks of Bulgaria are being pulled to the southwest by the movement of the Aegean Sea Plate and pushed to the northeast by the movement of the Apulian Plate. This has resulted in a number of faults bisecting the country, forming the Pernic Fault Zone, the Vitosha Fault Zone, the Zheleznitsa Fault Zone and the Sophia Graben (a Graben is an area of geological extension). The 22 May Earthquake is thought to have been caused by movement along the Pernic Fault.

Map showing the extensive faulting across Bulgaria. Bulgarian Academy of Science

See also Earthquake on the Modena Plane, northern Italy, Earthquake in northern Algeria, Southwest Poland hit by Earthquake, Zurich shaken by mild Earthquake and Earthquakes on Sciency Thoughts YouTube.

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Monday, 21 May 2012

The formation of a Keplerian Disk in the L1551 NE Protostellar System.

Protostars are areas within molecular clouds where stars are forming, areas of increased density surrounded by dusty envelopes of gas hundreds of AU across (AU stands for Astronomical Unit, 1 AU being the average distance between the Earth and the Sun). As these objects gain mass their gravity increases, causing more material to spiral inwards. This causes the disk of surrounding material to rotate faster and faster. Eventually the inner part of the disk rotates to fast for the outermost parts to keep up, causing this to be lost. The remaining, fast spinning inner disk is called a Keplerian Disk. Most of the material in this will spiral in and add to the mass of the developing star, though some may remain in orbit forming a planetary system.

L1551 is a molecular cloud containing a number of protostellar systems, in the constellation of Taurus, roughly 450 light years from Earth. One of these is the L1551 NE system, a binary system thought to be very young due to its coolness (~91 K, or -182°C) and the high ratio of matter in the surrounding disk compared to that in the two central protostars. In a paper published in the online arXiv database at Cornell University Library on 17 May 2012, a group of scientists led by Shigehisa Takakuwa of the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan discuss the results of a study of the L1551 NE system using the SubMillimeter Array on Mauna Kea, Hawaii.

The L1551 molecular cloud (center). L1551 NE is at the top left of the cloud (this is the northeast, east and west are reversed on sky images as they are looking up. Caltech.

Takakuwa et al. imaged the L1551 NE system at 330-335 GHz, enabling them to plot the density of ¹³CO and ¹⁸CO, hopefully proxies for the density of molecular material as a whole. This enabled them to map a Keplerian disk in the system measuring about 300 AU in diameter, and an outer disk measuring about 600 AU. The whole disk system has a mass roughly equivalent to 12% that of our Sun, the inner disk about 0.09%. The two protostars a combined mass equivalent to 80% of the Suns.

Diagram showing the extent of the disc around the two protostars of the L1551 NE system (A & B). Contours reflect density. The arrows the direction of material being ejected by L1551 NE A.

See also Fomalhaut b; not a planet after all? The strange debris disk of 99 Herculis, PSR J1719-1438b. The Diamond Planet, The Protostar HOPS-68 and Stars and Exoplanets on Sciency Thoughts YouTube.

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Sunday, 20 May 2012

New species of Dromaeosaur from the Early Cretaceous of Utah.

Dromaeosaurs were small Therapod Dinosaurs, thought to have been the group most closely related to the  birds. They had a distinctive enlarged and curved claw on the second toe of their hind feet that has earned them the nick-name 'raptors', and many of the group are known to have been feathered. Most Dromaeosaurs were small in size, some under a meter, though there were larger members of the group.

In a paper published in the journal PLoS One on 15 May 2012, a team of scientists led by Phil Senter of the Department of Biological Sciences at Fayetteville State University describe a new species of Dromaeosaur from the Early Cretaceous (Barremian-Aptian) Cedar Mountain Formation of the Arches National Park in Utah. The team also describe two other partial specimens that may represent new taxa, but which are not well enough preserved to allow the formal naming of species from them.

The new species is named as Yurgovuchia doellingi; from yurgovuch, the Ute word for Coyote (the animal is roughly Coyote size) and in honour of Helmut Doelling of the Utah Geological Survey. It is named from a selection of vertebra and a partial pubis.


Reconstruction of Yurgovuchia doellingi, from the available material. Cat for scale only. Senter et al. (2012).


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