Half billion year old fossils offer new clues to how life exploded on the sea floor

September 16, 2018

Artist reconstruction of Pahvantia hastasta. Credit: Masato Hattori

Stephen Pates, a researcher from Oxford University’s Department of Zoology, has uncovered secrets from the ancient oceans.

With Dr. Rudy Lerosey-Aubril from New England University (Australia), he meticulously re-examined fossil material collected over 25 years ago from the mountains of Utah, USA. The research, published in a new study in Nature Communications, reveals further evidence of the great complexity of the oldest animal ecosystems.

Twenty hours of work with a needle on the specimen while submerged underwater exposed numerous, delicate microscopic hair-like structures known as setae. This revelation of a frontal appendage with fine filtering setae has allowed researchers to confidently identify it as a radiodont – an extinct group of stem arthropods and distant relatives of modern crabs, insects and spiders.

“Our new study describes Pahvantia hastasta, a long-extinct relative of modern arthropods, which fed on microscopic organisms near the ocean’s surface,” says Stephen Pates. “We discovered that it used a fine mesh to capture much smaller plankton than any other known swimming animal of comparable size from the Cambrian period. This shows that large free-swimming animals helped to kick-start the diversification of life on the sea floor over half a billion years ago.”

Causes of the Cambrian Explosion—the rapid appearance in the fossil record of a diverse animal fauna around 540-500 million years ago—remain hotly debated. Although it probably included a combination of environmental and ecological factors, the establishment of a system to transfer energy from the area of primary production (the surface ocean) to that of highest diversity (the sea floor) played a crucial role.

Even though relatively small for a radiodont (FIG), Pahvantia was 10-1000 times larger than any mesoplanktonic primary consumers, and so would have made the transfer of energy from the surface oceans to the deep sea much more efficient. Primary producers such as unicellular algae are so small that once dead they are recycled locally and do not reach the deep ocean. In contrast large animals such as Pahvantia, which fed on them, produce large faecal pellets and carcasses, which sink rapidly and reached the seafloor, where they become food for bottom-dwelling animals.

Amateur enthusiasts provide research gold-dust

The presence of Pahvantia in the Cambrian of Utah has been known for decades thanks to the efforts of local amateur collectors Bob Harris and the legendary Gunther family.

“This work also provides an opportunity to celebrate the exceptional contribution of local and amateur collectors to modern palaeontology,” explains Stephen. “Without their tireless efforts, knowledge, and generosity, thousands of specimens representing hundreds of new species, would not be known to science.”

Bob Harris is rumoured to have turned down a job offer from the CIA, instead opening up a fossil shop and a number of quarries in the spectacular House Range, Utah. He discovered the first specimens of Pahvantia in the 1970s, and donated them to Richard Robison, a leading expert on Cambrian life from the University of Kansas. The Gunther family are famous for their extensive fossil collecting in Utah and Nevada. Over a dozen species have been named in honour of their contributions to palaeontology, as they have shared thousands of specimens with museums and schools over the years. Among these were specimens of Pahvantia which they uncovered between 1987 and 1997. Donated to the Kansas University Museum of Invertebrate Paleontology (KUMIP), these specimens are described for the first time in our study.

“I visited the KUMIP in the first year of my Ph.D.,” says Stephen. “It was awesome, exploring such a fantastic collection of fossils from the Cambrian of Utah and Nevada.”

The study has produced the most up-to-date analysis of evolutionary relationships between radiodonts. It shows that filter feeding evolved twice, possibly three times in this group, which otherwise essentially comprised fearsome predators such as Anomalocaris canadensis from the Burgess Shale in Canada.

Pahvantia adds to an ever-growing body of evidence that radiodonts were vital in the structure of Cambrian ecosystems, in this case linking the primary producers of the surface waters to the highly diverse fauna on the sea floor. It also shows the importance of museum collections like the KUMIP, and local collectors, such as Bob Harris and the Gunther family, in uncovering new and exciting findings about early animal life.

Reference:
Rudy Lerosey-Aubril et al. New suspension-feeding radiodont suggests evolution of microplanktivory in Cambrian macronekton, Nature Communications (2018). DOI: 10.1038/s41467-018-06229-7

Note: The above post is reprinted from materials provided by University of Oxford.

“World’s Largest Bird” Ancient bird bones redate human activity in Madagascar by 6,000 years

September 16, 2018

Disarticulation marks on the base of the tarsometatarsus. These cut marks were made when removing the toes from the foot. Credit: ZSL

Analysis of bones, from what was once the world’s largest bird, has revealed that humans arrived on the tropical island of Madagascar more than 6,000 years earlier than previously thought — according to a study published today, 12 September 2018, in the journal Science Advances.

A team of scientists led by international conservation charity ZSL (Zoological Society of London) discovered that ancient bones from the extinct Madagascan elephant birds (Aepyornis and Mullerornis) show cut marks and depression fractures consistent with hunting and butchery by prehistoric humans. Using radiocarbon dating techniques, the team were then able to determine when these giant birds had been killed, reassessing when humans first reached Madagascar.

Previous research on lemur bones and archaeological artefacts suggested that humans first arrived in Madagascar 2,400-4,000 years ago. However, the new study provides evidence of human presence on Madagascar as far back as 10,500 years ago — making these modified elephant bird bones the earliest known evidence of humans on the island.

Lead author Dr James Hansford from ZSL’s Institute of Zoology said: “We already know that Madagascar’s megafauna — elephant birds, hippos, giant tortoises and giant lemurs — became extinct less than 1,000 years ago. There are a number of theories about why this occurred, but the extent of human involvement hasn’t been clear.

“Our research provides evidence of human activity in Madagascar more than 6,000 years earlier than previously suspected — which demonstrates that a radically different extinction theory is required to understand the huge biodiversity loss that has occurred on the island. Humans seem to have coexisted with elephant birds and other now-extinct species for over 9,000 years, apparently with limited negative impact on biodiversity for most of this period, which offers new insights for conservation today.”

Co-author Professor Patricia Wright from Stony Brook University said: “This new discovery turns our idea of the first human arrivals on its head. We know that at the end of the Ice Age, when humans were only using stone tools, there were a group of humans that arrived on Madagascar. We do not know the origin of these people and won’t until we find further archaeological evidence, but we know there is no evidence of their genes in modern populations. The question remains — who these people were? And when and why did they disappear?”

The bones of the elephant birds studied by this project were originally found in 2009 in Christmas River in south-central Madagascar — a fossil ‘bone bed’ containing a rich concentration of ancient animal remains. This marsh site could have been a major kill site, but further research is required to confirm.

Reference:
James Hansford, Patricia C. Wright, Armand Rasoamiaramanana, Ventura R. Pérez, Laurie R. Godfrey, David Errickson, Tim Thompson, Samuel T. Turvey. Early Holocene human presence in Madagascar evidenced by exploitation of avian megafauna. Science Advances, 2018; 4 (9): eaat6925 DOI: 10.1126/sciadv.aat6925

Note: The above post is reprinted from materials provided by Zoological Society of London.

The walking dead: Fossils on the move can distort patterns of mass extinctions

September 16, 2018

fossil mollusks — Researchers drilled four 130-foot-long cores in the Po coastal basin in northeastern Italy, two on the current coastline and two farther inland, and sieved the sediment for mollusks. This sample captures fossils typical of an offshore environment. Credit: Image by Daniele Scarponi

Using the fossil record to accurately estimate the timing and pace of past mass extinctions is no easy task, and a new study highlights how fossil evidence can produce a misleading picture if not interpreted with care.

Florida Museum of Natural History researchers used a series of 130-foot cores drilled from the Po Plain in northeastern Italy to test a thought experiment: Imagine catastrophe strikes the Adriatic Sea, swiftly wiping out modern marine life. Could this hypothetical mass extinction be reconstructed correctly from mollusks — hard-shelled animals such as oysters and mussels — preserved in these cores?

When they examined the cores, the results were “somewhat unnerving,” said Michal Kowalewski, Thompson Chair of Invertebrate Paleontology and the study’s principal investigator.

Paleontologists use the age of a species’ last-known fossil to estimate the timing of extinction. A sudden extinction in the Adriatic Sea today should leave the youngest remains of many mollusk species in the sediments currently forming on the shore and seabed, the “ground zero” of the hypothetical extinction event. But the team found only six of 119 mollusk species — all of which are still alive in the area — at the top of the cores. Instead, the last fossil examples of many of these species often appeared in clusters dotted throughout the cores, suggesting smaller bursts of extinctions over a longer timeline, not a single massive die-off.

Taken at face value, the cores presented a dramatically distorted record of both the timing and tempo of extinction, potentially calling into question some of the methods paleontologists commonly use to interpret past mass extinctions.

“We’re not saying you cannot study mass extinctions. You can,” Kowalewski said. “What we’re saying is that the nature of the geological record is complicated, so it is not trivial to decipher it correctly.”

The results of their analysis did not come as a complete surprise. Computer models designed by paleontologists Steven Holland and Mark Patzkowsky had made similar predictions about how the final resting place of fossils — influenced by species’ ecological preferences, sea level and the makeup of sedimentary basins — could skew patterns of mass extinction.

“This is, to my knowledge, the first empirical study to use the fossil record of living species to test these models rigorously and computationally, rather than theoretically,” Kowalewski said. “We know these species are still living in the Adriatic Sea, so we can be sure that their disappearance from the fossil record does not represent a true extinction.”

Paleontologists have been grappling with the complications of interpreting mass extinctions in the fossil record for several decades. Even the extinction of the dinosaurs was thought to be a gradual, drawn-out process until evidence of a lethal meteor impact emerged in 1980. The problem is a phenomenon known as the Signor-Lipps effect: Because the fossil record is incompletely sampled, the last-known fossil of a given species is almost certainly not the last member of that species, which muddles our ability to date extinctions.

Applied on a larger scale, the Signor-Lipps effect can make abrupt mass extinctions appear gradual. A common approach to correct for this effect is to assume that where fossils end up — and are later discovered — is random, and mathematically adjust estimates of extinction timing accordingly.

But it’s more complicated than that, Kowalewski said, because the fossil record is not created in a random way.

Climatic cycles trigger changes in sea level, causing shorelines to advance or recede and driving changes in environments. A beach may become a mudflat, for example, or a delta can turn into a coastal plain. Shifts in sea level can also affect sedimentation rates — how quickly mud and sand are deposited. These factors can cause last occurrences of fossils to cluster together and influence the probability of finding fossils in a given location.

When the researchers reordered the species represented in the cores from the Po basin according to their last occurrence, they noted several points at which many species appeared to vanish simultaneously. In reality, none of the species had gone extinct. They disappeared from a given site either because local environmental conditions changed, or they were simply missed during the sampling, said Rafal Nawrot, the study’s first author and a postdoctoral researcher in invertebrate paleontology at the Florida Museum.

The cores also depicted a false pattern of extinction, with the majority of offshore species disappearing in a single large “pulse” in the lower part of the cores and shallow-water and brackish species fading out in several smaller pulses. This is because species followed their preferred habitats as they shifted with changing sea levels. Deeper-water dwellers vanished first, as the local river delta started to expand into the Adriatic Sea, replacing open sea with coastal conditions. When shorelines advanced even farther, shallow-water species disappeared as well.

“It’s important to admit that fossil species — just like modern ones — have specific ecological requirements, which sounds obvious but is not always acknowledged,” Nawrot said.

Current methods may give researchers the illusion of precision but fail to account for these factors, which are crucial to correctly interpreting past extinction events, he said.

“If you apply methods based on the assumption of random fossilization, you get a precise estimate, but it may be wrong by millions of years,” Nawrot said. “Not only the pattern of extinction but also the timing of extinction would be wrongly interpreted, so this is quite important.”

While the findings are sobering, the situation is far from hopeless, Kowalewski said. When the team incorporated methods that accounted for species’ ecological preferences, distribution and abundance into the analysis, the results were a much closer approximation of what exists in the basin today.

“This provides us with an initial guideline of how to analyze these types of data to get a more realistic assessment of extinction events,” Kowalewski said. “Certainly, this is a work in progress.”

Reference:
Rafał Nawrot, Daniele Scarponi, Michele Azzarone, Troy A. Dexter, Kristopher M. Kusnerik, Jacalyn M. Wittmer, Alessandro Amorosi, Michał Kowalewski. Stratigraphic signatures of mass extinctions: ecological and sedimentary determinants. Proceedings of the Royal Society B: Biological Sciences, 2018; 285 (1886): 20181191 DOI: 10.1098/rspb.2018.1191

Note: The above post is reprinted from materials provided by Florida Museum of Natural History.

New plant species discovered in museum is probably extinct

September 16, 2018

This is Thismia kobensis when it was discovered in 1992. At the time of discovery it was assumed to be a member not of the genus Thismia but the genus Oxygyne. Credit: Kobe University

A single non-photosynthetic plant specimen preserved in a Japanese natural history museum has been identified as a new species. However, it is highly possible that this species is already extinct. These findings were published on September 13 in Phytotaxa.

This plant was discovered in Kobe, Japan, in 1992, and preserved with its identity unknown. No new specimens were found in follow-up surveys between 1993 and 1999, and the plant’s original habitat was destroyed by land development in 1999.

A research team led by Project Associate Professor Kenji Suetsugu (Kobe University Graduate School of Science) is carrying out surveys to classify the taxonomy and ecology of non-photosynthetic plants called mycoheterotrophs. These plants do not photosynthesize, instead leading a parasitic existence drawing nutrients from fungi and tree roots. Many species only appear above ground during brief fruiting and flowering periods, making them very hard to find and identify.

As part of the survey, Professor Suetsugu, in collaboration with Dr. Nobuhira Kurosaki (Visiting Professor at the University of Hyogo) and independent botanists Mr. Osamu Nakanishi and Mr. Tomiki Kobayashi, re-examined a plant specimen preserved in the Museum of Nature and Human Activities, Hyogo. The specimen in this study was originally found in 1992 in the Nishi district of Kobe by the above-mentioned Mr. Nakanishi and Mr. Kobayashi, accompanied by Mr. Takashi Saburomaru.

When first discovered, the plant was identified as belonging to the family Burmanniaceae because of its non-photosynthesizing properties and the unusual shape of its flowers. It seemed to be closely related to the Oxygyne hyodoi species discovered in Japan’s Aichi prefecture, but it was not clear whether the specimen was O. hyodoi itself or something else. This time, after close scrutiny of the plant’s morphological characteristics, the team showed that it was not a member of Oxygene but Thismia, mainly due to the position and shape of the anthers. After dissecting the flower and closely studying the shape of the petals and stamen, they realized that it had characteristics not found in any other species of Thismia identified so far. The team named it Thismia kobensis after its place of discovery, and presented it as a new species.

Thismia kobensis was discovered in 1992 as a single specimen, with no further samples of the same species found. In 2010 it was reported as extinct by Hyogo prefecture. “Because it has now been recognized as a new species, we are hopeful that living specimens of T. kobensis can be discovered in other places.” says Professor Suetsugu.

Mycoheterotrophic plants are parasites — in order to survive they need a stable ecosystem with abundant resources, and they are very sensitive to environmental changes. Therefore, a large number of mycoheterotrophs are now in danger of extinction, and this study strongly suggests that some mycoheterotrophic species may be dying out before they are recognized.

Many plant specimens are preserved in museums. Even if the original collector is unable to identify the specimen, samples stored by public organizations can be identified by future generations. This discovery of a new species, based on a specimen of a plant that is presumably extinct, highlights the importance of collecting specimens in order to fully understand the biodiversity of our environment.

Reference:
Kenji Suetsugu, Osamu Nakanishi, Tomiki Kobayashi, Nobuhira Kurosaki. Thismia kobensis (Burmanniaceae), a new and presumably extinct species from Hyogo Prefecture, Japan. Phytotaxa, 2018 DOI: 10.11646/phytotaxa.369.2.6

Note: The above post is reprinted from materials provided by Kobe University.

Injection wells can induce earthquakes miles away from the well

August 30, 2018

In this diagram of an injection operation, the blue and red areas represent the spatial footprint of induced seismicity for injection into basement rock (blue) or the overlying sedimentary layer (red). Gray lines represent the fault network. The graphs below show the corresponding earthquake probabilities as a function of distance from the well. Credit: Goebel and Brodsky, Science, 2018

A study of earthquakes induced by injecting fluids deep underground has revealed surprising patterns, suggesting that current recommendations for hydraulic fracturing, wastewater disposal, and geothermal wells may need to be revised.

Researchers at UC Santa Cruz compiled and analyzed data from around the world for earthquakes clearly associated with injection wells. They found that a single injection well can cause earthquakes at distances more than 6 miles (10 kilometers) from the well. They also found that, in general, injecting fluids into sedimentary rock can cause larger, more distant earthquakes than injecting into the underlying basement rock.

“This is problematic, since the current advice is to preferentially inject into the sedimentary sequence as a theoretically safer alternative to the basement rock,” said Emily Brodsky, professor of Earth and planetary sciences at UC Santa Cruz.

Postdoctoral researcher Thomas Goebel said the key issue is the spatial footprint of induced seismicity around the injection well. “It’s not that the basement rock is safe, because there is still the possibility of encountering a fault in the basement rock that can cause a large earthquake, but the probability is reduced because the spatial footprint is smaller,” he said.

In a paper published August 31 in Science, Goebel and Brodsky described two distinct patterns of induced seismicity, which they associated with different physical mechanisms acting in basement rock and sedimentary rock. In the first pattern, associated with injection into basement rock, earthquakes tend to occur in a compact cluster around the well, with a steep decline in earthquakes farther from the well. In the other pattern, associated with sedimentary rock, induced earthquakes decline gradually with distance from the well and occur at much greater distances.

The physical mechanism by which injection wells induce earthquakes was thought to be a direct result of increased fluid pressure in the pores of the rock, causing faults to slip more easily. This mechanism can account for the spatial pattern of seismicity seen with injection into basement rock, Goebel said. But the pattern seen with injection into sedimentary rock suggests a different mechanism resulting from efficient “poroelastic coupling,” which controls the ability of the rock to transmit fluid stresses into the solid rock matrix.

“When you inject water into the ground, it pushes on the surrounding rock and creates elastic stress in the rock, which can put pressure on faults at a distance without putting water into those faults. So if poroelasticity is dominant, you end up with a larger footprint because it’s loading neighboring faults beyond the area of increased pore pressure,” Brodsky said.

According to Goebel, the crystalline basement rock is stiffer and has lower porosity than sedimentary rock. “Therefore, the increase in pore pressure is limited to isolated pockets around the well, and the coupling of that with the overall stress field is low,” he said.

Goebel said their findings help explain the extent of induced seismicity in regions such as Oklahoma where there are many injection sites in oil and gas fields. Oklahoma has seen a dramatic surge in earthquakes since 2010, to the extent that there are now more earthquakes each year in Oklahoma than in California. Goebel and Brodsky did not include sites in Oklahoma in their study, however, because there are so many injection wells they couldn’t isolate the effects of individual wells.

“In Oklahoma, they are injecting into the high-porosity sedimentary unit above the basement, but these elastic stresses can be transmitted over a large distance, so you could activate a large basement fault at a distance of 10 kilometers,” Goebel said. “That may be what we’re seeing in places like Oklahoma.”

Reference:
Thomas H. W. Goebel, Emily E. Brodsky. The spatial footprint of injection wells in a global compilation of induced earthquake sequences. Science, 2018; 361 (6405): 899 DOI: 10.1126/science.aat5449

Note: The above post is reprinted from materials provided by University of California – Santa Cruz. Original written by Tim Stephens.

Early amber trade: Sicilian amber in Western Europe predates arrival of Baltic amber by at least 2,000 years

August 30, 2018

Amber and other unusual materials such as jade, obsidian and rock crystal have attracted interest as raw materials for the manufacture of decorative items since Late Prehistory and, indeed, amber retains a high value in present-day jewellery.

‘Baltic’ amber from Scandinavia is often cited as a key material circulating in prehistoric Europe, but in a new study published today in PLOS ONE researchers have found that amber from Sicily was travelling around the Western Mediterranean as early as the 4th Millennium BC — at least 2,000 years before the arrival of any Baltic amber in Iberia.

According to lead author Dr Mercedes Murillo-Barroso of the Universidad de Granada, “The new evidence presented in this study has allowed the most comprehensive review to date on the provision and exchange of amber in the Prehistory of Iberia. Thanks to this new work, we now have evidence of the arrival of Sicilian amber in Iberia from at least the 4th Millennium BC.”

“Interestingly, the first amber objects recovered in Sicily and identified as being made from the local amber there (known as simetite) also date from the 4th Millennium BC, however, there is no other evidence indicating direct contact between Sicily and Iberia at this time.”

“Instead, what we do know about are the links between the Iberian Peninsula and North Africa. It is plausible that Sicilian amber reached Iberia through exchanges with North Africa. This amber appears at southern Iberian sites and its distribution is similar to that of ivory objects, suggesting that both materials reached the Iberian Peninsula following the same or similar channels.”

Senior author Professor Marcos Martinón-Torres, of the Department of Archaeology, University of Cambridge adds, “It is only from the Late Bronze Age that we see Baltic amber at a large number of Iberian sites and it is likely that it arrived via the Mediterranean, rather than through direct trade with Scandinavia.”

“What’s peculiar is that this amber appears as associated with iron, silver and ceramics pointing to Mediterranean connections. This suggests that amber from the North may have moved South across Central Europe before being shipped to the West by Mediterranean sailors, challenging previous suggestions of direct trade between Scandinavia and Iberia.”

Murillo-Barroso concludes, “In this study, we’ve been able to overcome traditional challenges in attempts at assigning corroded amber to a geological source. These new analytical techniques can be used a reference to identify Sicilian amber, even from highly deteriorated archaeological samples.”

“There are still unresolved issues to be investigated in the future — namely exploring the presence of amber in North African contexts from the same time period and further researching the networks involved in the introduction and spread of Baltic amber in Iberia and the extent to which metals or other Iberian commodities were provided in return.”

Reference:
Mercedes Murillo-Barroso, Enrique Peñalver, Primitiva Bueno, Rosa Barroso, Rodrigo de Balbín, Marcos Martinón-Torres. Amber in prehistoric Iberia: New data and a review. PLOS ONE, 2018; 13 (8): e0202235 DOI: 10.1371/journal.pone.0202235

Note: The above post is reprinted from materials provided by University of Cambridge. The original story is licensed under a Creative Commons License.

Three previously unknown ancient primates identified

August 30, 2018

Kirk's father and Austin-based artist Randy Kirk produced his own rendering of what the species might have looked like. — Kirk’s father and Austin-based artist Randy Kirk produced his own rendering of what the species might have looked like. Credit: Painting on marble by Randwulph.

Biological anthropologists from The University of Texas at Austin have described three new species of fossil primates that were previously unknown to science. All of the new primates were residents of San Diego County at a time when southern California was filled with lush tropical forests.

Since the 1930s, numerous primate fossils have been uncovered in the sandstones and claystones that make up the Friars Formation in San Diego County. Paleontologist Stephen Walsh and fieldworkers from the San Diego Museum of Natural History (SDNHM) built up a large collection of fossil primates from the San Diego area, but Walsh was unable to describe these specimens before his death in 2007.

A decade later, UT Austin graduate student Amy Atwater and anthropology professor Chris Kirk took up the challenge, describing and naming three previously unknown omomyoid primates that lived 42 million to 46 million years ago. The researchers named these new species Ekwiiyemakius walshi, Gunnelltarsius randalli and Brontomomys cerutti.

These findings double the number of known primate genera represented in the Friars Formation and increase the total number of known omomyine primates of that period from 15 to 18.

Atwater and Kirk’s descriptions were published in the Journal of Human Evolution.

“The addition of these primates provides for a better understanding of primate richness in the middle Eocene,” said Atwater, who is now the paleontology collection manager at the Museum of the Rockies in Bozeman, Montana. “Previous research in the Rocky Mountain basins suggested the primate richness declined during this time period, but we argue that primate richness increased concurrently in other locations.”

Studying the teeth, researchers concluded the three new genera, which represent the bulk of the undescribed Friars Formation omomyoid sample at SDNHM, range in size from 113 to 796 grams and are most likely related to a group of extinct species comprising the primate subfamily Omomyinae.

“Teeth can tell us a lot about evolutionary history and give us a good handle on the size and diet of an extinct primate,” Kirk said. “Enamel is the hardest tissue in the body. And as a result, teeth are more likely to be preserved in the fossil record.”

Ekwiiyemakius walshi, the smallest of the three new species, was estimated to weigh between 113 and 125 grams — comparable in size to some modern bushbabies. It was named for Walsh, who collected and prepared many of the specimens, and also derives from the Native American Kumeyaay tribe’s place name, Ekwiiyemak — meaning “behind the clouds” — for the location of the headwaters of the San Diego and Sweetwater Rivers.

Gunnelltarsius randalli was named for Gregg Gunnell, the researchers’ late colleague and expert on Eocene mammals, and for SDNHM fossil collections manager Kesler Randall. It was estimated to weigh between 275 and 303 grams, about the size of today’s fat-tailed dwarf lemur.

Brontomomys cerutti was large compared with most other omomyoids and was estimated to weigh between 719 and 796 grams — about the size of a living sportive lemur. Due to its large size, its name derives from the Greek word bront?, or “thunder,” as well as for Richard Cerutti, the retired SDNHM paleontologist responsible for collecting many of the Brontomomys specimens.

Reference:
Amy L. Atwater, E. Christopher Kirk. New middle Eocene omomyines (Primates, Haplorhini) from San Diego County, California. Journal of Human Evolution, 2018; DOI: 10.1016/j.jhevol.2018.04.010

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Mammal forerunner that reproduced like a reptile sheds light on brain evolution

August 30, 2018

Researchers from The University of Texas at Austin found a fossil of an extinct mammal relative with a clutch of 38 babies that were near miniatures of their mother. Credit: Eva Hoffman / The University of Texas at Austin

Compared with the rest of the animal kingdom, mammals have the biggest brains and produce some of the smallest litters of offspring. A newly described fossil of an extinct mammal relative — and her 38 babies — is among the best evidence that a key development in the evolution of mammals was trading brood power for brain power.

The find is among the rarest of the rare because it contains the only known fossils of babies from any mammal precursor, said researchers from The University of Texas at Austin who discovered and studied the fossilized family. But the presence of so many babies — more than twice the average litter size of any living mammal — revealed that it reproduced in a manner akin to reptiles. Researchers think the babies were probably developing inside eggs or had just recently hatched when they died.

The study, published in the journal Nature on Aug. 29, describes specimens that researchers say may help reveal how mammals evolved a different approach to reproduction than their ancestors, which produced large numbers of offspring.

“These babies are from a really important point in the evolutionary tree,” said Eva Hoffman, who led research on the fossil as a graduate student at the UT Jackson School of Geosciences. “They had a lot of features similar to modern mammals, features that are relevant in understanding mammalian evolution.”

Hoffman co-authored the study with her graduate adviser, Jackson School Professor Timothy Rowe.

The mammal relative belonged to an extinct species of beagle-size plant-eaters called Kayentatherium wellesi that lived alongside dinosaurs about 185 million years ago. Like mammals, Kayentatherium probably had hair.

When Rowe collected the fossil more than 18 years ago from a rock formation in Arizona, he thought that he was bringing a single specimen back with him. He had no idea about the dozens of babies it contained.

Sebastian Egberts, a former graduate student and fossil preparator at the Jackson School, spotted the first sign of the babies years later when a grain-sized speck of tooth enamel caught his eye in 2009 as he was unpacking the fossil.

“It didn’t look like a pointy fish tooth or a small tooth from a primitive reptile,” said Egberts, who is now an instructor of anatomy at the Philadelphia College of Osteopathic Medicine. “It looked more like a molariform tooth (molar-like tooth) — and that got me very excited.”

A CT scan of the fossil revealed a handful of bones inside the rock. However, it took advances in CT-imaging technology during the next 18 years, the expertise of technicians at UT Austin’s High-Resolution X-ray Computed Tomography Facility, and extensive digital processing by Hoffman to reveal the rest of the babies — not only jaws and teeth, but complete skulls and partial skeletons.

The 3D visualizations Hoffman produced allowed her to conduct an in-depth analysis of the fossil that verified that the tiny bones belonged to babies and were the same species as the adult. Her analysis also revealed that the skulls of the babies were like scaled-down replicas of the adult, with skulls a tenth the size but otherwise proportional. This finding is in contrast to mammals, which have babies that are born with shortened faces and bulbous heads to account for big brains.

The brain is an energy-intensive organ, and pregnancy — not to mention childrearing — is an energy-intensive process. The discovery that Kayentatherium had a tiny brain and many babies, despite otherwise having much in common with mammals, suggests that a critical step in the evolution of mammals was trading big litters for big brains, and that this step happened later in mammalian evolution.

“Just a few million years later, in mammals, they unquestionably had big brains, and they unquestionably had a small litter size,” Rowe said.

The mammalian approach to reproduction directly relates to human development — including the development of our own brains. By looking back at our early mammalian ancestors, humans can learn more about the evolutionary process that helped shape who we are as a species, Rowe said.

“There are additional deep stories on the evolution of development, and the evolution of mammalian intelligence and behavior and physiology that can be squeezed out of a remarkable fossil like this now that we have the technology to study it,” he said.

Funding for the research was provided by the National Science Foundation, The University of Texas Geology Foundation and the Jackson School of Geosciences.

Reference:
Eva A. Hoffman, Timothy B. Rowe. Jurassic stem-mammal perinates and the origin of mammalian reproduction and growth. Nature, 2018; DOI: 10.1038/s41586-018-0441-3

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Faster than we thought—sulfurization of organic material

August 30, 2018

A view of the Issole River in southeastern France, where this research team studied sediments from the Pont d’Issole section, about 500 meters southeast of the village of La Bâtie Thorame‐Basse, Alpes de Haute Provence. Credit: Shutterstock

About 94 million years ago, something happened that led to an unusually high amount of organic material being preserved in oceans around the world.

The burial of this organic carbon—over about a half million years—pulled an enormous amount of CO2 out of the atmosphere and had a major impact on Earth’s climate.

The basic assumption has been that some combination of super-giant algae blooms and low levels of oxygen in the ocean allowed the organic carbon from these blooms to be preserved in sediments.

New research from the department of Earth and Planetary Sciences at Washington University in St. Louis shows that there is another process by which this carbon was preserved. Organic matter sulfurization—which previously had been thought to act over timescales of tens of thousands of years—can actually occur much faster, according to research published earlier this week in the journal Nature Communications.

This change in timescales may have sizable implications for how scientists understand the past and future of the Earth’s climate.

Organic matter sulfurization reactions can occur on the timescale of just hours to days, according to the paper, “Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization.”

“We can even induce them in 24 hours in the lab,” said Morgan Reed Raven, assistant professor in earth science at the University of California, Santa Barbara.

Raven headed this research as the Agouron Geobiology Fellow at Washington University.

The finding focused on a layer of sediment in the south of France from that time period, about 94 million years ago, known as the Ocean Anoxic Event 2 (OAE2). The site is more typical of other places and times on the planet then sites where many previous studies focused. For this reason, Raven said, “There are all sorts of places on Earth today where rapid sulfurization is on the table as a major mechanism for impacting how much carbon is preserved.”

The potential widespread nature of sulfurization as a manner of carbon preservation means that our understanding of the history of oxygen in the ocean may need to be reevaluated.

The amount of sedimentary carbon has acted as a kind of proxy for oxygen levels in the ocean. The more carbon in the sediment, the thinking went, the less oxygen was in the ocean. (If there’s no oxygen, there are no microbes or animals to eat organic material, so when that material dies, it accumulates in the ocean floor).

“That is probably still correct,” said David Fike, International Center for Energy, Environment & Sustainability (InCEES) Professor in the Department of Earth and Planetary Sciences in Arts & Sciences, associate director of InCEES and director of the Environmental Studies program.

“But Morgan showed this other process,” he said. “Even with oxygen in the system, if there is sulfur in the organic matter, nothing can easily eat it,” and the matter will still be preserved in the sediment.

“People have known about sulfurization, but they thought it was slow and not that important environmentally,” Fike said. “What Morgan has been able to show is that it is a much more efficient and powerful way to lock up matter, to trap the organics.”

Going forward, he said, this work highlights an additional process that will be important to include in climate modelling.

“We hope that through this paper and others,” Fike said, “modelers will see this as an important process to incorporate into their systems.”

Raven has done research in a variety of environments, the results of which will be published in forthcoming papers. “The hypotheses that came out of this paper do seem to be holding up,” she said. “And for understanding the formation of many extremely organic carbon-rich sediments, these rapid sulfur reactions are where the story is at.”

Reference:
Morgan Reed Raven et al, Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization, Nature Communications (2018). DOI: 10.1038/s41467-018-05943-6

Note: The above post is reprinted from materials provided by Washington University in St. Louis.

Geologists uncover new clues about largest mass extinction ever

August 28, 2018

The photo depicts a sample of mantle xenolith, rock sections of the lithosphere that get captured by the passing magma and erupted to the surface during the volcanic explosion. Credit: Michael W. Broadley.

A new study could help explain the driving force behind the largest mass extinction in the history of earth, known as the End-Permian Extinction.

The event, also known as the Great Dying, occurred around 250 million years ago when a massive volcanic eruption in what is today the Russian province of Siberia sent nearly 90 percent of all life right into extinction. Geologists call this eruption the Siberian Flood Basalts, and it ran for almost a million years.

“The scale of this extinction was so incredible that scientists have often wondered what made the Siberian Flood Basalts so much more deadly than other similar eruptions,” said Michael Broadley, a postdoctoral researcher at the Centre for Petrographic and Geochemical Research in Vandœuvre-lès-Nancy, France, and lead author of the paper.

The work, which was published in Nature Geoscience, was co-authored by Lawrence (Larry) Taylor, the former director of the Planetary Geosciences Institute at the University of Tennessee, Knoxville. Taylor, whose prolific career at UT spanned 46 years, passed away in September 2017 at age 79.

According to Broadley, “Taylor was instrumental in supplying samples of mantle xenoliths, rock sections of the lithosphere [a section of the planet located between the crust and the mantle] that get captured by the passing magma and erupted to the surface during the volcanic explosion. Taylor also provided advice throughout the study.”

Through the analysis of samples, Broadley and his team tried to determine the composition of the lithosphere. They found that before the Siberian Flood Basalts took place, the Siberian lithosphere was heavily loaded with chlorine, bromine, and iodine, all chemical elements from the halogen group. However, these elements seem to have disappeared after the volcanic eruption.

“We concluded that the large reservoir of halogens that was stored in the Siberian lithosphere was sent into the earth’s atmosphere during the volcanic explosion, effectively destroying the ozone layer at the time and contributing to the mass extinction,” Broadley said.

Reference:
Michael W. Broadley, Peter H. Barry, Chris J. Ballentine, Lawrence A. Taylor, Ray Burgess. End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles. Nature Geoscience, 2018; DOI: 10.1038/s41561-018-0215-4

Note: The above post is reprinted from materials provided by University of Tennessee at Knoxville.

Upper Cretaceous trench deposits of the Neo-Tethyan subduction zone

August 28, 2018

Paleogeographic scenario for the Jiachala Formation. a) Jiachala Formation, b)&c) other trench deposits to the west. Credit: Science China Press

The Jiachala Formation, which was fed largely from the Gangdese arc, has long been considered to comprise syn-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts and pollen assemblages. Because magmatic activity in the Gangdese arc continued through the Late Cretaceous and Paleogene, this scenario is incompatible with U-Pb ages of detrital zircons invariably older than the latest Cretaceous.

In order to solve this incongruence and constrain the depositional age and tectonic setting of the Jiachala Formation, a new study was carried out with stratigraphic, sedimentological, provenance analysis including sandstone petrography, detrital zircon U-Pb age and Hf isotopic data. Paleontological analysis was conducted by Prof. Xiumian Hu’s group at Nanjing University.

According to this research, the Jiachala Formation was originally deposited on a submarine fan in the trench environment at the active southern margin of the Asian plate. Sandstone petrography, detrital-zircon U-Pb ages and Hf isotope ratios indicate provenance from the Gangdese arc and the central Lhasa terrane. Because magmatic activity in the Gangdese arc was virtually continuous, the youngest population of detrital zircons contained in the Jiachala Formation constrain its depositional age as Late Cretaceous (~88-84 Ma). What’s more, based on the U-Pb age spectra of detrital zircons and sandstone petrography, there are no Paleocene-Eocene units similar to the Jiachala Formation that compare well with Upper Cretaceous exposed within and close to the Yalung Zangbo suture zone (Figure 1).

Integrated geological information indicates that the Jiachala Formation accumulated in the Neo-Tethyan trench during subduction of oceanic lithosphere (Figure 1).In summary, this research gives a new interpretation about the Jiachala Formation and enriches the case study of the arc trench system of the active Asian continental margin.

Reference:
Hanpu Fu et al, Upper Cretaceous trench deposits of the Neo-Tethyan subduction zone: Jiachala Formation from Yarlung Zangbo suture zone in Tibet, China, Science China Earth Sciences (2018). DOI: 10.1007/s11430-017-9223-5

Note: The above post is reprinted from materials provided by Science China Press.

Lombok quakes not necessarily leading to a big bang

August 28, 2018

The Mount Rinjani crater in Lombok, Indonesia. Credit: Monash University

Table of Contents

In recent weeks, the volcanic island of Lombok, in Indonesia, has been battered by a series of powerful earthquakes, each greater than M6 and each located deep beneath Lombok’s volcanic complex. The very presence of the volcano naturally leads to public concerns that these earthquakes are in some way related and we could expect an eruption to follow.

Lombok, a popular tourist destination for many Australians, shot to worldwide attention when two devastating quakes killed nearly 500 people (the first M6.4 on 29 July and the second almost M7 on 5 August). Pictures were seen on Australian media of clearly distressed Aussies queuing at the airport to get out as quickly as possible.

The reality on the ground, however, was far worse, with reports of more than 350,000 people displaced by the quakes. On 19 August, two more large earthquakes rocked the island, the first M6.3 and the second even larger at M6.9.

For those who live through earthquakes, the greatest anxieties often come from the long, drawn-out period of aftershocks that follow the main event. Many Indonesians have been living in makeshift shelters, uncertain of whether their homes are structurally stable, and painfully aware that fresh, damaging quakes happen any moment.

In the ring of fire

Lombok is perhaps not as well-known as its western neighbour, Bali, but remains a beautiful destination of choice. This island, like many of the Indonesian archipelago, lies on the infamous ring of fire. Just south of Lombok, tectonic plates are colliding at some of the fastest rates in the world (greater than 7cm per year), in a process known as subduction, where one plate slides under the other deep into the mantle. It’s the stresses from subduction that causes many earthquakes to occur, and it’s the heating up of the subducting plate and subsequent melting that leads to many volcanoes on the overlying plate.

As a result, Indonesia is used to both earthquakes and volcanic activity. On Lombok, the Rinjani volcanic complex rises on the northeastern side of the island, and indeed its natural beauty is one of the features that attracts tourists to the island.

Unfortunately, this particular volcanic complex also has some infamy. Mount Samalas, which is part of the complex, is thought to have erupted in 1275 with an explosion more powerful than Krakatoa – possibly triggering the northern hemisphere’s Little Ice Age.

The question of whether the earthquakes could signify a pending volcanic eruption is no small matter. We have no reliable method of predicting when a volcanic eruption or an earthquake will occur, due to the complexity of the Earth.

Nonetheless, we can look for clues. Earthquakes have been known to trigger or at least predate small eruptions.

Some concentrated sequences of earthquakes are also thought to track the movement of molten rock through the Earth. In this case, the earthquakes are somewhat unusual. In a standard earthquake sequence we expect the first earthquake, the mainshock, to be followed by a series of aftershocks of smaller magnitudes that tail off with time.

However, here, the first M6.4 earthquake was followed by a larger M6.9 earthquake, and a fortnight later two other earthquakes of similar magnitude. Each of these earthquakes was at different depths within the crust but at roughly the same location, on the northeastern side of Lombok, almost directly beneath Rinjani.

Key indicators

Thankfully, before anyone leaps to conclusions, we can use some of the outstanding global datasets that geoscientists collect to infer whether these earthquakes are indicators of magma rising into Rinjani.

First of all, there’s no obvious vertical time progression of seismicity that could indicate rising magma. Instead, the aftershocks from this earthquake sequence appear to be migrating laterally away from Lombok towards the east and the neighbouring island of Sumbawa.

Secondly, we can examine seismic signals from the earthquakes and determine how much fault slip is occurring relative to fault opening, using what scientists refer to as moment tensor solutions. This isn’t an exact science, but if magma were triggering the earthquakes we may expect to see some component of opening on the faults. In this case the moment tensor solutions seem to show the faults were mostly purely slipping.

Finally, the orientations of the faults hosting the earthquakes and the direction they slipped in are all consistent with the regional stress state caused by subduction, and could easily just be stress-triggered events rather than anything to do with magma.

For the moment, this series of earthquakes remains an alarming but mysterious sequence. The key thing now is for the local and international authorities to be allowed to carefully monitor the situation.

We have a number of tools at our disposal that help. These include looking for increases in gas emissions at Mount Rinjani, and using instruments such as tiltmeters to check whether ground deformation is occurring.

We hope these events will indeed die down and life for the locals can return to normal, with the support of the Indonesian government and international aid, including Australia’s. One day I hope to visit Lombok and climb its mountains, to see one of the Earth’s great wonders sleeping.

Note: The above post is reprinted from materials provided by Monash University.

How did alvarezsaurian dinosaurs evolve monodactyl hand?

August 24, 2018

This is a Bannykus resoration. Credit: SHI Aijuan

Digit reduction occurs many times in tetrapod evolution, and the most famous example is the ‘horse series’ of North America. An international research team announced the discovery of two new Chinese dinosaurs: Bannykus and Xiyunykus, in the journal Current Biology, which shed light on how alvarezsaurian dinosaurs reduced and lost their fingers.

The new dinosaurs are based on two fossils collected by a joint research team led by XU Xing from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) of the Chinese Academy of Sciences. Xiynykus was discovered in 2005 in Zhunggar Basin, northwestern China, and Bannykus was discovered a few years later in 2009 in western Inner Mongolia, north-central China.

The new Alvarezsaurian dinosaurs are among the most bizarre groups of theropods, with extremely short, robust forelimbs with a single functional claw and gracile, bird-like skulls and hindlimbs. These specializations have led to controversy about their phylogenetic placement, biogeographic history, and ecological role in Mesozoic ecosystems.

AT early times, unspecialized alvarezsaur fossils were the key to resolving this controversy, but until recently the group had at least a 90 million year gap in its fossil record, especially during the Early Cretaceous.

The new dinosaurs fall nearly at the midpoint of the 90-million year temporal gap between the earliest and latest alvarezsaurs. They contribute key phylogenetic and biogeographic information that firmly resolves Alvarezsauria as a monophyletic clade originating in Asia and dispersing to other continents.

The new findings show that clear anatomical specializations also present in later members of the clade, such as a hypertrophied first digit, mechanically efficient forearm, and robust humerus. However, they preserve plesiomorphic forelimb proportions not present in later-branching members.

Together, these observations document a major macroevolutionary shift from the plesiomorphic theropod condition of a relatively long arm and grasping hand in the earliest alvarezsaurs (e.g., Haplocheirus), to a long arm with a specialized hand in Bannykus and Xiyunykus, to the highly specialized short-limbed, functionally monodactyl hand in the latest evolving members of the clade. “This transition plays out in an incremental fashion over more than 50 million years,” said XU, “it could one day potentially serve as a classic example of macroevolution akin to the ‘horse series’ of North America.” “Alvarezsaurs are weird animals,” said Dr. Jonah Choiniere from the University of the Witwatersrand of South Africa, a co-author of the report, “with their strong, clawed hands and weak jaws, they appear to be the dinosaurian analogue to today’s aardvarks and anteaters.”

But the earliest alvarezsaurs had more typical, meat-eating teeth and hands useful for catching small prey, and only later-evolving alvarezsaurs evolved a hand with a huge, single claw capable perhaps of tearing open rotting logs and anthills. Bannykus and Xiyunykus are important because they show transitional steps in the process of alvarezsaurs adapting to new diets. “The fossil record is the best source of information about how anatomical features evolve,” said James Clark from George Washington University, “and like other classic examples of evolution such as the ‘horse series,’ these dinosaurs show us how a lineage can make a major shift in its ecology over time.”

Dr. Roger Benson from the University of Oxford said, “The new fossils have long arms, showing that alvarezsaurs evolved short arms only later in their evoutionary history, in species with small body sizes. This is quite different to what happens in the classic example of tyrannosaurs, which have short arms and giant size.”

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

Rare intermediate fossils give researchers insight into evolution of bird-like dinosaur

August 24, 2018

An international team of researchers discovered a new species of dinosaur, Xiyunykus pengi, during an expedition to Xinjiang, China. The discovery is the latest stemming from a partnership between the George Washington University and the Chinese Academy of Sciences. The findings were published today in Current Biology along with the description of a second new intermediate species, Bannykus wulatensis.

Xiyunykus and Bannykus are both alvarezsaurs, an enigmatic group of dinosaurs that share many characteristics with birds. Their bodies are slender, with a bird-like skull and many small teeth instead of the usual large, sharp cutting teeth of their meat-eating relatives.

“When we described the first well-known alvarezsaur, Mononykus, in 1993, we were amazed at the contrast between its mole-like arms and its roadrunner-like body, but there were few fossils connecting it back to other theropod groups,” James Clark, the Ronald Weintraub Professor of Biology at the GW Columbian College of Arts and Sciences, said.

However, alvarezsaurs did not always look this way. Early members of the group had relatively long arms with strong-clawed hands and typical meat-eating teeth. Over time, the alvarezsaurs evolved into dinosaurs with mole-like arms and a single claw. The discovery of the new specimens allowed the researchers to uncover an important shift in how the specialized features of the alvarezsaurs evolved.

“It can be hard to pin down the relationships of highly specialized animals. But fossil species with transitional features, like Xiyunykus and Bannykus, are tremendously helpful because they link bizarre anatomical features to more typical ones,” Jonah Choiniere, an associate professor at Wits University and member of the research team, said.

The fossils were discovered during an expedition co-led by Dr. Clark and Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences. Xiyunykus pengi is the ninth species of dinosaur identified by the partnership between GW and the academy.

“Our international field teams have been tremendously productive over the years,” Dr. Xu said. “This research showcases just some of our incredible discoveries.”

The fieldwork and research were supported by U.S. National Science Foundation grant EAR 0922187.

Reference:
Xing Xu, Jonah Choiniere, Qingwei Tan, Roger B.J. Benson, James Clark, Corwin Sullivan, Qi Zhao, Fenglu Han, Qingyu Ma, Yiming He, Shuo Wang, Hai Xing, Lin Tan. Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution. Current Biology, 2018; DOI: 10.1016/j.cub.2018.07.057

Note: The above post is reprinted from materials provided by George Washington University.

Research into deadly 2016 Italian earthquakes could improve future seismic forecasts

August 24, 2018

Location of survey site at rupture across a road near Castelluccio, Italy. The rupture occurred during the third earthquake in the seismic sequence and gives researchers a record of the deformation. Credit: Laura Gregory, University of Leeds

The timing and size of three deadly earthquakes that struck Italy in 2016 may have been pre-determined, according to new research that could improve future earthquake forecasts.

A joint British-Italian team of geologists and seismologists have shown that the clustering of the three quakes might have been caused by the arrangement of a cross-cutting network of underground faults.

The findings show that although all three earthquakes occurred on the same major fault, several smaller faults prevented a single massive earthquake from occurring instead and also acted as pathways for naturally occurring fluids that triggered later earthquakes.

The cluster of three earthquakes, termed a “seismic sequence” by seismologists, each had magnitudes greater than six and killed more than 300 people in Italy’s Apennine mountains between 24 August and 30 October 2016.

The research, led by Durham University, UK, comes ahead of the second anniversary of the start of the earthquake sequence.

The study is published in the journal Earth and Planetary Science Letters.

The researchers say the findings could have wider implications for the study of seismic hazards, enabling scientists to better understand potential earthquake sequences following a quake.

Dr Richard Walters, Assistant Professor in the Department of Earth Sciences, Durham University, said: “These results address a long-standing mystery in earthquake science — why a major fault system sometimes fails in a single large earthquake that ruptures its entire length, versus failing in multiple smaller earthquakes drawn-out over months or years.

“Our results imply that even though we couldn’t have predicted when the earthquake sequence would start, once it got going, both the size and timing of the major earthquakes may have been pre-determined by the arrangement of faults at depth.

“This is all information we could hypothetically know before the event, and therefore, this could be a hugely important avenue for improving future earthquake forecasts.”

Dr Walters and the team used satellite data to estimate which part of the fault failed in each earthquake, and compared this pattern with the location and timing of thousands of tiny aftershocks throughout the seismic sequence.

They found that intersections of small faults with the main fault system separated each of the three largest earthquakes, strongly suggesting these intersections stop the growth of each earthquake and prevent the faults failing in a single large event.

But in addition, the scientists also found that after the first earthquake, thousands of aftershocks crept northwards along these same fault intersections at a rate of around 100 metres per day, in a manner consistent with naturally occurring water and gas being pumped along the faults by the first earthquake on 24 August, 2016.

The second earthquake, on the 26 October, occurred exactly when these fluids reached its location, therefore controlling the relative timing of failure.

Dr Walters added: “It was a big surprise that these relatively small faults were having such a huge influence over the whole sequence.

“They stop the first earthquake in its tracks, and then they channel the fluids that start the sequence up again months later. No-one’s ever seen this before.”

Co-author Dr Laura Gregory, in the School of Earth and Environment, at the University of Leeds, UK, said it was important to understand whether or not a fault fails in a seismic sequence, and that the team’s results were only made possible by combining a varied array of different datasets.

Dr Gregory said: “A seismic sequence has vastly different implications for seismic hazard compared to a single large earthquake. If the faults in Italy in 2016 had failed together in one big event, the impact on the local population would have been much worse.

“This is the first time we’ve ever had this quality of modern data over one of these earthquake sequences, and bringing together a range of specialists was key for unpicking how the earthquakes related to one another.

“I was scrambling over the mountainside immediately after each earthquake with British and Italian colleagues, measuring the metre-high cliffs that had suddenly formed. Meanwhile, other members of our team were analysing data from seismometers stationed around the world, or were mapping the tiny bending of the ground around the faults using satellites orbiting the planet at 500 miles altitude.”

The research was partly supported by the UK’s Natural Environment Research Council, via an Urgency Grant, and through the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET).

Reference:
R.J. Walters, L.C. Gregory, L.N.J. Wedmore, T.J. Craig, K. McCaffrey, M. Wilkinson, J. Chen, Z. Li, J.R. Elliott, H. Goodall, F. Iezzi, F. Livio, A.M. Michetti, G. Roberts, E. Vittori. Dual control of fault intersections on stop-start rupture in the 2016 Central Italy seismic sequence. Earth and Planetary Science Letters, 2018; 500: 1 DOI: 10.1016/j.epsl.2018.07.043

Note: The above post is reprinted from materials provided by Durham University.

Two new Chinese dinosaurs discovered

August 24, 2018

From left to right: Haplocheirus, Xiyunykus, Bannykus, and Shuvuuia. Note the lengthening of the jaws, reduction of the teeth, and changes in the hand and arm. Credit: Viktor Radermacher

Professor Jonah Choiniere from the University of the Witwatersrand, Johannesburg, South Africa was a leading member of the team and is a co-author on the research.

The dinosaurs are both alvarezsaurs, an enigmatic group of theropod [meat-eating] dinosaurs, which have many similarities with birds and which show adaptations thought to be related to eating insects that live in colonies.

“Alvarezsaurs are weird animals,” said Choiniere. “With their strong, clawed hands and weak jaws, they appear to be the dinosaurian analogue to today’s aardvarks and anteaters.”

But alvarezsaurs did not originally eat insects. The earliest members of the group had more typically meat-eating teeth and hands, useful for catching small prey. Only later-evolving members reduced their teeth and evolved a hand with a huge, single claw capable – perhaps – of tearing open rotting logs and anthills.

“The new fossils have long arms, and so show that alvarezsaurs evolved short arms only later in their evolutionary history, in species with small body sizes. This is quite different to what happens in the classic example of tyrannosaurs, which have short arms and giant size,” said co-author Professor Roger Benson of Oxford University.

Bannykus and Xiyunykus are important because they show transitional steps in the process of alvarezsaurs adapting to new diets.

“The fossil record is the best source of information about how anatomical features evolve,” said James Clark, co-author and an Honorary Professor at Wits University. “And like other classic examples of evolution such as the ‘horse series’, these dinosaurs show us how a lineage can make a major shift in its ecology over time.”

The specimens were discovered during collaborative international fieldwork in China. Xiyunykus was discovered in 2005 in Xinjiang, north-western China. Bannykus was discovered a few years later, in 2009, in Inner Mongolia, north-central China.

Both research trips were joint expeditions co-led by Professors Xu Xing (Institute for Vertebrate Palaeontology and Palaeoanthropology, Beijing) and James Clark (George Washington University, Washington DC).

“Our international field teams have been tremendously productive over the years,” said Xing. “And this research showcases just some of our incredible discoveries.”

Once the fossils were discovered, their further study was made possible by a joint South Africa/China collaborative grant through South Africa’s National Research Foundation, held by Choiniere and Xu.

“The joint research programme has helped in so many ways,” said Choiniere. “China and South Africa have a great deal of overlap in palaeontology, and it has been a privilege to cross-train students over the last two years.”

Note: The above post is reprinted from materials provided by University of the Witwatersrand.

Landslides triggered by human activity on the rise

August 24, 2018

Photograph panorama looking over the devastation of the Kedarnath landslide, June 2013, Uttarakhand state, India. Credit: Vaibhav Kaul, University of Sheffield

More than 50,000 people were killed by landslides around the world between 2004 and 2016, according to a new study by researchers at UK’s Sheffield University. The team, who compiled data on over 4800 fatal landslides during the 13-year period, also revealed for the first time that landslides resulting from human activity have increased over time. The research is published today in the European Geosciences Union journal Natural Hazards and Earth System Sciences.

The team found that over 700 fatal landslides that occurred between 2004 and 2016 had a human fingerprint. Construction works, legal and illegal mining, as well as the unregulated cutting of hills (carving out land on a slope) caused most of the human-induced landslides.

“We were aware that humans are placing increasing pressure on their local environment, but it was surprising to find clear trends within the database that fatal landslides triggered by construction, illegal hillcutting and illegal mining were increasing globally during the period of 2004 and 2016,” says Melanie Froude, a postdoctoral researcher at Sheffield’s Department of Geography and lead author of the study.

While the trend is global, Asia is the most affected continent: “All countries in the top 10 for fatal landslide triggered by human activity are located in Asia,” says Froude. The number 1 country is India, which accounts for 20% of these events. It is also the country where human-triggered fatal landslides are increasing at the highest rate, followed by Pakistan, Myanmar and the Philippines.

Dave Petley, a professor and Vice-President for Research and Innovation at the University of Sheffield, started collecting data on fatal landslides after realising that many databases on natural disasters were “significantly underestimating the extent of landslide impact.” While earthquakes and storms are deadlier, landslides do cause a significant number of fatalities.

The researchers identified a total of 4800 fatal landslides, excluding those triggered by earthquakes, that occurred around the world between 2004 and 2016 and caused a total of about 56,000 deaths. The most tragic event identified by the researchers was the Kedarnath landslide in June 2013 in India, which resulted in over 5000 deaths. It was due to extreme weather conditions that caused flash floods and massive mudflows, which affected thousands of religious pilgrims trapped in a mountain area.

Since 2004, Petley has painstakingly collected data on fatal landslides from online English-language media reports. To confirm the news were accurate, Petley — and more recently Froude, who reviewed all landslide accounts — checked each report whenever possible against government and aid agency articles, academic studies or through personal communication. Details about the landslides, such as location, impacts or cause, were added to their Global Fatal Landslide Database.

“Collecting these reports and organising them into a database shows us where landslides are frequently harming people, what causes these landslides and whether there are patterns in fatal landslide occurrence over time. The database provides us with an overview of the impact of landslides on society,” explains Petley.

Aside from Asia, where 75% of landslides in the database occurred, the areas most affected are in Central and South America, the Caribbean islands, and East Africa. In Europe, the Alps are the region with more fatal landslides.

In support of past studies, the researchers also found that 79% of landslides in their database were triggered by rainfall. Most events happen during the northern hemisphere summer, when cyclones, hurricanes and typhoons are more frequent and the monsoon season brings heavy rains to parts of Asia.

The Natural Hazards and Earth System Sciences study highlights that fatal landslides are more common in settlements, along roads, and at sites rich in precious resources. They occur more frequently in poor countries and affect poor people disproportionately, the researchers say.

In the Himalayan mountain region, especially in Nepal and India, many of the fatal landslides triggered by construction occurred on road construction sites in rural areas, while in China many happened in urban building sites. “The prevalence of landslides in these settings suggests that regulations to protect workers and the public are insufficient or are not being sufficiently enforced. In the case of roads, maintaining safety during construction is difficult when it is economically unviable to completely shut roads because alternative routes involve substantial 100 mile + detours,” says Froude.

Landslides triggered by hillcutting are mostly a problem in rural areas, where many people illegally collect material from hillslopes to build their houses. “We found several incidents of children being caught-up in slides triggered as they collected coloured clay from hillslopes, for decoration of houses during religious festivals in Nepal. Educating communities who undertake this practise on how to do it safely, will save lives,” Froude says.

“With appropriate regulation to guide engineering design, education and enforcement of regulation by specialist inspectors, landslides triggered by construction, mining and hillcutting are entirely preventable,” Froude emphasises. “The study highlights that we need to refocus our efforts globally on preventable slope accidents,” concludes Petley.

Reference:
Melanie J. Froude, David N. Petley. Global fatal landslide occurrence from 2004 to 2016. Natural Hazards and Earth System Sciences, 2018; 18 (8): 2161 DOI: 10.5194/nhess-18-2161-2018

Note: The above post is reprinted from materials provided by European Geosciences Union.

228 million year old fossil sheds light on how turtles evolved

August 23, 2018

Illustration showing what Eorhynchochelys would have looked like in life. Credit: Adrienne Stroup, Field Museum

There are a couple of key features that make a turtle a turtle: its shell, for one, but also its toothless beak. A newly-discovered fossil turtle that lived 228 million years ago is shedding light on how modern turtles developed these traits. It had a beak, but while its body was Frisbee-shaped, its wide ribs hadn’t grown to form a shell like we see in turtles today.

“This creature was over six feet long, it had a strange disc-like body and a long tail, and the anterior part of its jaws developed into this strange beak,” says Olivier Rieppel, a paleontologist at Chicago’s Field Museum and one of the authors of a new paper in Nature. “It probably lived in shallow water and dug in the mud for food.”

The new species has been christened Eorhynchochelys sinensis — a mouthful, but with a straightforward meaning. Eorhynchochelys (“Ay-oh-rink-oh-keel-is”) means “dawn beak turtle” — essentially, first turtle with a beak — while sinensis, meaning “from China,” refers to the place where it was found by the study’s lead author, Li Chun of China’s Institute of Vertebrate Paleontology and Paleoanthropology.

Eorhynchochelys isn’t the only kind of early turtle that scientists have discovered — there is another early turtle with a partial shell but no beak. Until now, it’s been unclear how they all fit into the reptile family tree. “The origin of turtles has been an unsolved problem in paleontology for many decades,” says Rieppel. “Now with Eorhynchochelys, how turtles evolved has become a lot clearer.”

The fact that Eorhynchochelys developed a beak before other early turtles but didn’t have a shell is evidence of mosaic evolution — the idea that traits can evolve independently from each other and at a different rate, and that not every ancestral species has the same combination of these traits. Modern turtles have both shells and beaks, but the path evolution took to get there wasn’t a straight line. Instead, some turtle relatives got partial shells while others got beaks, and eventually, the genetic mutations that create these traits occurred in the same animal.

“This impressively large fossil is a very exciting discovery giving us another piece in the puzzle of turtle evolution,” says Nick Fraser, an author of the study from National Museums Scotland. “It shows that early turtle evolution was not a straightforward, step-by-step accumulation of unique traits but was a much more complex series of events that we are only just beginning to unravel.”

Fine details in the skull of Eorhynchochelys solved another turtle evolution mystery. For years, scientists weren’t sure if turtle ancestors were part of the same reptile group as modern lizards and snakes — diapsids, which early in their evolution had two holes on the sides of their skulls — or if they were anapsids that lack these openings. Eorhynchochelys’s skull shows signs that it was a diapsid. “With Eorhynchochelys’s diapsid skull, we know that turtles are not related to the early anapsid reptiles, but are instead related to evolutionarily more advanced diapsid reptiles. This is cemented, the debate is over,” says Rieppel.

The study’s authors say that their findings, both about how and when turtles developed shells and their status as diapsids, will change how scientists think about this branch of animals. “I was surprised myself,” says Rieppel. “Eorhynchochelys makes the turtle family tree make sense. Until I saw this fossil, I didn’t buy some of its relatives as turtles. Now, I do.”

This study was contributed to by Institute of Vertebrate Paleontology and Paleoanthropology, the CAS Center for Excellence in Life and Paleoenvironment, National Museums Scotland, the Field Museum, and the Canadian Museum of Nature.

Reference:
Chun Li, Nicholas C. Fraser, Olivier Rieppel, Xiao-Chun Wu. A Triassic stem turtle with an edentulous beak. Nature, 2018; 560 (7719): 476 DOI: 10.1038/s41586-018-0419-1

Note: The above post is reprinted from materials provided by Field Museum.

Amber unveils evolution of ancient antlions

August 23, 2018

Reconstruction of two lacewing larvae. Credit: YANG Dinghua

Myrmeleontiformia, consisting of antlions and their relatives, are an ancient group of lacewing insects characterized by predatory larvae with unusual morphologies and behaviors. An international team led by Prof. WANG Bo from the Chinese Academy of Sciences (NIGPAS) and two Italian researchers found fossil Myrmeleontiformia fauna from the mid-Cretaceous (approximately 100 million years ago) preserved in Burmese amber. The study was published in Nature Communications on August 22, 2018.

Their findings show that Myrmeleontiformia did not gain considerable morphological novelty during the subsequent 100 million years, and their diversity seemed to result from different combinations of a limited set of character traits in a complex trade-off. This morphological stasis helped in reconstructing behaviors not preserved by a trace in the fossil record. Inference of these behaviors sheds light on the ecological niche and lifestyle of extinct Myrmeleontiformia.

Statistical correlation analysis strongly supports a correlation between a selection of morphological traits and two hunting strategies of these ambush predators—camouflaging and fossoriality—allowing the researchers to reconstruct habits of the extinct species.

The findings suggested that fossorial specializations evolved more than once across Myrmeleontiformia from arboreal ancestors. The fossorial lifestyle of antlions was certainly one of the factors leading to their success, allowing these insects to colonize and diversify in arid habitats where they survived considerable changes in terrestrial environments during the Cretaceous lineages.

The Burmese fossils showed that debris carrying characterized this lineage for at least 100 million years. All of these camouflaging lacewings were equipped with elongate protuberances. The strong statistical correlation between the presence of these protuberances and camouflaging behavior demonstrated that this trait is an indicator of such behavior, even when the debris covering is not directly preserved in the amber piece together with the larvae.

This research also implies that camouflaging behavior arose at least three times within Myrmeleontiformia. Camouflaging and fossoriality appear widespread across the lineage, and both behaviors allowed the predatory larvae to hide from their unsuspecting prey.

Reference:
Davide Badano et al, Diverse Cretaceous larvae reveal the evolutionary and behavioural history of antlions and lacewings, Nature Communications (2018). DOI: 10.1038/s41467-018-05484-y

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

A timescale for the origin and evolution of all of life on Earth

August 23, 2018

Earth from near space.
Credit: © dell / Fotolia

A new study led by scientists from the University of Bristol has used a combination of genomic and fossil data to explain the history of life on Earth, from its origin to the present day.

Palaeontologists have long sought to understand ancient life and the shared evolutionary history of life as a whole.

However, the fossil record of early life is extremely fragmented, and its quality significantly deteriorates further back in time towards the Archaean period, more than 2.5 billion years ago, when the Earth’s crust had cooled enough to allow the formation of continents and the only life forms were microbes.

Holly Betts, lead author of the study, from the University of Bristol’s School of Earth Sciences, said: “There are few fossils from the Archaean and they generally cannot be unambiguously assigned to the lineages we are familiar with, like the blue-green algae or the salt-loving archaebacteria that colours salt-marshes pink all around the world.

“The problem with the early fossil record of life is that it is so limited and difficult to interpret — careful reanalysis of the some of the very oldest fossils has shown them to be crystals, not fossils at all.”

Fossil evidence for the early history of life is so fragmented and difficult to evaluate that new discoveries and reinterpretations of known fossils have led to a proliferation of conflicting ideas about the timescale of the early history of life.

Co-author Professor Philip Donoghue, also from Bristol’s School of Earth Sciences, added: “Fossils do not represent the only line of evidence to understand the past. A second record of life exists, preserved in the genomes of all living creatures.”

Co-author Dr Tom Williams, from Bristol’s School of Biological Sciences, said: “Combining fossil and genomic information, we can use an approach called the ‘molecular clock’ which is loosely based on the idea that the number of differences in the genomes of two living species (say a human and a bacterium) are proportional to the time since they shared a common ancestor.”

By making use of this method the team at Bristol and Mark Puttick from the University of Bath were able to derive a timescale for the history of life on Earth that did not rely on the ever-changing age of the oldest accepted fossil evidence of life.

Co-author Professor Davide Pisani said: “Using this approach we were able to show that the Last Universal Common Ancestor all cellular life forms, ‘LUCA’, existed very early in Earth’s history, almost 4.5 Billion years ago — not long after Earth was impacted by the planet Theia, the event which sterilised Earth and led to the formation of the Moon.

“This is significantly earlier than the currently accepted oldest fossil evidence would suggest.

“Our results indicate that two “primary” lineages of life emerged from LUCA (the Eubacteria and the Archaebacteria), approximately one Billion years after LUCA.

“This result is testament to the power of genomic information, as it is impossible, based on the available fossil information, to discriminate between the oldest eubacterial and archaebacterial fossil remains.”

The study confirms modern views that the eukaryotes, the lineage to which human life belongs (together with the plants and the fungi, for example), is not a primary lineage of life. Professor Pisani added: “It is rather humbling to think we belong to a lineage that is billions of years younger than life itself.”

Reference:
Holly C. Betts, Mark N. Puttick, James W. Clark, Tom A. Williams, Philip C. J. Donoghue, Davide Pisani. Integrated genomic and fossil evidence illuminates life’s early evolution and eukaryote origin. Nature Ecology & Evolution, 2018; DOI: 10.1038/s41559-018-0644-x

Note: The above post is reprinted from materials provided by University of Bristol.

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