New Cretaceous mammal fossil sheds light on evolution of middle ear

By: Thomas Schmitt Attorney on November 27, 2019 / comment : 0 China, Early Mammals, Fossils, Palaeontology

Researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and the American Museum of Natural History (AMNH) have reported a new species of multituberculate - a type of extinct Mesozoic rodent - with well-preserved middle ear bones from the Cretaceous Jehol Biota of China. The findings were published in Nature.

Reconstruction of Jeholbaatar kielanae [Credit: XU Yong]

The new mammal, Jeholbaatar kielanae, has a middle ear that is distinct from those of its relatives. WANG Yuanqing and WANG Haibing from IVPP, along with MENG Jin from AMNH, proposed that the evolution of its auditory apparatus might have been driven by specialization for feeding.

Fossil evidence shows that postdentary bones were either embedded in the postdentary trough on the medial side of the dentary or connected to the dentary via an ossified Meckel's cartilage in early mammals, prior to their migration into the cranium as seen in extant mammals.

Detachment of the mammalian middle ear bones from the dentary occurred independently at least three times. But how and why this process took place in different clades of mammals remains unclear.

The Jeholbaatar kielanae specimen was discovered in the Jiufotang Formation in China's Liaoning Province (Jehol Biota). It displays the first well-preserved middle-ear bones in multituberculates, providing solid evidence of the morphology and articulation of these bony elements, which are fully detached from the dentary.

It reveals a unique configuration with more complete components than those previously reported in multituberculates. The new fossil reveals a transitional stage in the evolution of the surangular - a "reptilian" jawbone.

In light of current evidence, scientists argue that the primary (malleus-incus) and secondary (squamosal-dentary) jaw joints co-evolved in allotherians, allowing a distinct palinal (anteroposterior) jaw movement while chewing.

Detachment of the auditory apparatus of the middle ear would have gained higher selective pressure in order to increase feeding efficiency, suggesting that evolution of the middle ear was probably triggered by functional constraints on the feeding apparatus in allotherians.

Source: Chinese Academy of Sciences [November 27, 2019]

New study shows a carnivorous dinosaur species regrew all its teeth every few months

By: Thomas Schmitt Attorney on November 27, 2019 / comment : 0 Dinosaurs, Fossils, Madagascar, Palaeontology

A meat-eating dinosaur species that lived in Madagascar some 70 million years ago replaced all its teeth every couple of months or so, a new study has found, surprising even the researchers.

Credit: Sae Bom Ra

In fact, Majungasaurus grew new teeth roughly two to 13 times faster than those of other carnivorous dinosaurs, says paper lead author Michael D. D'Emic, an assistant professor of biology at Adelphi University. Majungasaurus would form a new tooth in each socket every couple of months.

"This meant they were wearing down their teeth quickly, possibly because they were gnawing on bones," D'Emic says. "There is independent evidence for this in the form of scratches and gouges that match the spacing and size of their teeth on a variety of bones - bones from animals that would have been their prey."

Some animals today, too, will gnaw on bones, including rodents, D'Emic explains. It's a way for them to ingest certain nutrients. It also requires exceptionally strong teeth - but Majungasaurus did not have those.

"That's our working hypothesis for why they had such elevated rates of replacement," D'Emic says. The rapid-fire tooth growth puts Majungasaurus in same league with sharks and big, herbivorous dinosaurs, he adds.

CT scan-generated models of the jaws of Majungasaurus (left), Ceratosaurus (center) and Allosaurus (right), with microscopic views of the interior of their teeth below each model. Stripes running from upper left to lower right in each microscopic image are daily deposited incremental lines, which allow the amount of time it took for a tooth to grow to be reconstructed [Credit: D’Emic et al. 2019]

Although at least a few hundred meat-eating dinosaur species roamed the Earth, researchers have analyzed tooth-replacement rates for only about a half-dozen of them, D'Emic says. He also has looked into tooth-replacement patterns in plant-eating dinosaurs.

"I'm hoping this latest project spurs more people to study other species. I bet that will reveal further surprises," he says. "And hopefully that will lead to a better understanding of how dinosaurs evolved to be successful for so long."

Importantly, the recent study examined two additional species of predatory dinosaur (Allosaurus and Ceratosaurus), providing an opportunity to consider tooth-growth patterns at a broader scale.

In collaboration with Patrick O'Connor, professor of anatomy at Ohio University, and Ph.D. student Eric Lund, D'Emic used a collection of isolated fossil teeth to examine microscopic growth lines in the teeth. These growth lines are similar to tree rings, but instead of being deposited once a year, they were deposited daily. At the same, the team used computerized tomography (CT) on intact jaws to visualize unerupted teeth growing deep inside the bones. That allowed them to estimate tooth-replacement rates in a large number of individual jaws so they could cross-check their results.

People and climate led to Australia's megafauna extinction

By: Thomas Schmitt Attorney on November 27, 2019 / comment : 0 Australia, Climate Change, Early Mammals, Fossils, Palaeontology

The mystery of the role of people and climate in the fate of Australian megafauna might have been solved in a breakthrough study.

Pleistocene kangaroo was the largest and most heavily built kangaroo known [Credit: Flinders University]

'Megafauna', giant beasts that once roamed the continent -- including wombat-like creatures as big as cars, birds more than two metres tall, and lizards more than seven metres long -- became extinct about 42,000 years ago. But the role of people in their demise has been hotly debated for decades.

For the first time, the research suggests a combination of climate change and the impact of people sealed the fate of megafauna, at least in south-eastern Australia. And that distribution of freshwater -- a precious commodity for animals and people alike as the climate warmed -- can explain regional differences in the timing at which megafauna died out.

The new study, led by a team of researchers from the ARC Centre of Excellence for Australian Biodiversity and Heritage (CABAH), analysed fossil data, climate reconstructions, and archaeological information describing patterns in human migration across south-eastern Australia.

The team developed and applied sophisticated mathematical models to test scenarios to explain regional variation in the periods during which people and megafauna coexisted.


"There has been much debate among scientists about what conditions led to this extinction event," said lead author Dr Frederik Saltre, Research Fellow and Coordinator of the Global Ecology Lab at Flinders University.

"Resolving this question is important because it is one of the oldest such extinction events anywhere after modern human beings evolved and left Africa", he added.

The findings, published in Nature Communications, are the result of analysis and complex modelling based on data including more than 10,000 fossils and archaeological records. Using high-quality fossil data and archaeological evidence of human activity, the researchers were able to map regional patterns of megafauna extinction.

They developed sophisticated models to test the impact of factors including climate, water availability, and human activity on localised patterns of megafauna extinction.

Credit: Flinders University

The extinction pattern could only be explained by the combination of people sharing the environment and the reduced of availability of freshwater due to climate change.

"The regional patterns in extinction are best explained by the hypothesis that people migrated across Australia, exploiting lakes and other sources of drinking water connecting the drier regions in between," said co-investigator Professor Corey Bradshaw of the Global Ecology Lab at Flinders University.

"It is plausible that megafauna species were attracted to the same freshwater sources as humans, thus increasing the chance of interactions."

The new insight that human pressure and climate change work together to trigger species extinction is a "stark warning" for the immediate future of the planet's biodiversity facing even stronger climate and habitat disruption, Dr Saltre concluded.

Source: Flinders University [November 27, 2019]

Animal-like embryos evolved before animals

By: Thomas Schmitt Attorney on November 27, 2019 / comment : 0 China, Fossils, Palaeontology

Animals evolved from single-celled ancestors, before diversifying into 30 or 40 distinct anatomical designs. When and how animal ancestors made the transition from single-celled microbes to complex multicellular organisms has been the focus of intense debate.

Three-dimensional reconstruction of a Caveasphaera specimen, showing cell structures [Credit: NIGPAS]

Until now, this question could only be addressed by studying living animals and their relatives, but now the research team has found evidence that a key step in this major evolutionary transition occurred long before complex animals appear in the fossil record, in the fossilised embryos that resemble multicellular stages in the life cycle of single-celled relatives of animals.

The team discovered the fossils named Caveasphaera in 609 million-year old rocks in the Guizhou Province of South China. Individual Caveasphaera fossils are only about half a millimeter in diameter, but X-ray microscopy revealed that they were preserved all the way down to their component cells.

Kelly Vargas, from the University of Bristol's School of Earth Sciences, said: "X-Ray tomographic microscopy works like a medical CT scanner, but allows us to see features that are less than a thousandth of a millimeter in size. We were able to sort the fossils into growth stages, reconstructing the embryology of Caveasphaera."

Co-author Zongjun Yin, from Nanjing Institute of Geology and Palaeontology in China, added: "Our results show that Caveasphaera sorted its cells during embryo development, in just the same way as living animals, including humans, but we have no evidence that these embryos developed into more complex organisms."

Computer models based on X-ray tomographic microscopy of the fossils, showing the successive stages of development [Credit: Philip Donoghue & Zongjun Yin]

Co-author Dr John Cunningham, also from University of Bristol, said: "Caveasphaera had a life cycle like the close living relatives of animals, which alternate between single-celled and multicellular stages. However, Caveasphaera goes one step further, reorganising those cells during embryology."

Co-author Stefan Bengtson, from the Swedish Museum of Natural History, said "Caveasphaera is the earliest evidence of this most important step in the evolution of animals, which allowed them to develop distinct tissue layers and organs".

Co-author Maoyan Zhu, also from Nanjing Institute of Geology and Palaeontology, said he is not totally convinced that Caveasphaera is an animal. He added: "Caveasphaera looks a lot like the embryos of some starfish and corals - we don't find the adult stages simply because they are harder to fossilise

Co-author Dr Federica Marone from the Paul Scherrer Institute in Switzerland said "this study shows the amazing detail that can be preserved in the fossil record but also the power of X-ray microscopes in uncovering secrets preserved in stone without destroying the fossils."

a) and b), SEM image(s) of naked Caveasphaera specimen(s) with cellular structures; e), f) showing detail of the cellular structures; c) and d), Caveasphaera specimens with well-preserved envelope [Credit: NIGPAS]

Co-author Professor Philip Donoghue, also from the University of Bristol's School of Earth Sciences, said "Caveasphaera shows features that look both like microbial relatives of animals and early embryo stages of primitive animals. We're still searching for more fossils that may help us to decide.

"Either way, fossils of Caveasphaera tell us that animal-like embryonic development evolved long before the oldest definitive animals appear in the fossil record."

The findings are published in Current Biology.

Source: University of Bristol [November 27, 2019]

World's oldest comma shrimp was way ahead of the curve

By: Thomas Schmitt Attorney on November 26, 2019 / comment : 0 Colombia, Fossils, Palaeontology

Scientists have discovered the world's oldest "comma" shrimp, a tiny crustacean shaped like its punctuation namesake. The 90-million-year-old creature fills in a major evolutionary gap for a family of marine animals now found in abundance around the planet, according to researchers from Yale and the University of Alaska. The discovery appears in the journal Proceedings of the Royal Society B.

Eobodotria muisca [Credit: Javier Luque]

The fossilized shrimp, named Eobodotria muisca, comes from Mesozoic rocks in tropical South America. Researchers found exceptionally well-preserved fossils representing more than 500 individuals between 6 and 8 millimeters long, with features that are rarely preserved in fossil crustaceans: mouthparts, the gut, tiny hairs, and small compound eyes.

"We are amazed by how similar Eobodotria muisca is to today's species," said Yale paleontologist Javier Luque, lead author of the study. "There are eight families or main groups of living comma shrimp, and none of them have a confirmed fossil occurrence. This means we had no idea when modern comma shrimp evolved, until now."

The only previous record of a modern-looking comma shrimp is a 160-million-year-old fossil from Europe, Luque said. Although that shrimp fit within the range of comma shrimp body forms, it couldn't be linked to any of the main modern families of comma shrimp.

Eobodotria muisca, on the other hand, belongs to the Bodotriidae family of living comma shrimp, Luque said, extending the fossil record of that family of shrimp by nearly 100 million years.

The new species lived during the mid-Cretaceous period, when a long, narrow inland sea covered a large part of what is today the Eastern and Central Andes of Colombia. Luque found the fossils together with fossils of the crab Callichimaera perplexa. Eobodotria muisca is named after the Muisca native Americans who lived in the Colombian Andes.

Luque said that the similarity between Eobodotria muisca and its modern relatives suggests that the rates of external anatomical changes over millions of years in this group was low compared to other crustacean groups found in the same location. He also noted that the new cache of fossils is the first of its kind in northern South America.

Sarah Gerken of the University of Alaska-Anchorage is co-author of the study.

Gerken and Luque said most of the Eobodotria muisca fossils they found were adult males. Large aggregations of males usually happen in the water column when they are searching for females by means of their large antennae for smelling and their flappy tail appendages for swimming—both features that females lack, the researchers explained.

One possible explanation for this unusual accumulation of adult males is that they could have died suddenly in the water column while swarming in search of females, and then sunk down to the soft bottom where they fossilized, Gerken and Luque said.

The researchers said the discovery not only helps paleontologists understand the origin of the comma shrimp's curved body, it also can be used to help understand the origins of related crustaceans on the evolutionary family tree.

Author: Jim Shelton | Source: Yale University [November 26, 2019]

Did human hunting activities alone drive great auks' extinction?

By: Thomas Schmitt Attorney on November 26, 2019 / comment : 0 Early Birds, Fossils, Genetics, Iceland, North America, Palaeontology, Scotland

New insight on the extinction history of a flightless seabird that vanished from the shores of the North Atlantic during the 19th century has been published in eLife.

A mounted great auk skin, The Brussels Auk (RBINS 5355), from the collections at the Royal Belgian Institute of Natural Sciences (RBINS) [Credit: Thierry Hubin, RBINS]

The findings suggest that intense hunting by humans could have caused the rapid extinction of the great auk, showing how even species that exist in large and widespread populations can be vulnerable to exploitation.

Great auks were large, flightless diving birds thought to have existed in the millions. They were distributed around the North Atlantic, with breeding colonies along the east coast of North America and especially on the islands off Newfoundland. They could also be found on islands off the coasts of Iceland and Scotland, as well as throughout Scandinavia.

But these birds had a long history of being hunted by humans. They were poached for their meat and eggs during prehistoric times, and this activity was further intensified in 1500 AD by European seamen visiting the fishing grounds of Newfoundland. Their feathers later became highly sought after in the 1700s, contributing further to their demise.

"Despite the well-documented history of exploitation since the 16th century, it is unclear whether hunting alone could have been responsible for the species' extinction, or whether the birds were already in decline due to natural environmental changes," says lead author Jessica Thomas, who completed the work as part of her PhD studies at Bangor University, UK, and the University of Copenhagen, Denmark, and is now a postdoctoral researcher at Swansea University, Wales, UK.

Great auk humeri from Funk Island. These samples are part of the great auk collection at the American Museum of Natural History [Credit: J. Thomas]

To investigate this further, Thomas and her collaborators carried out combined analyses of ancient genetic data, GPS-based ocean current data, and population viability - a process that looks at the probability of a population going extinct within a given number of years. They sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and used their analyses to reconstruct the birds' population structure and dynamics throughout the Holocene period, the last 11,700 years of Earth's history.

"Taken together, our data don't suggest that great auks were at risk of extinction prior to intensive human hunting behaviour in the early 16th century," explains co-senior author Thomas Gilbert, Professor of Evolutionary Genomics at the University of Copenhagen. "But critically, this doesn't mean that we've provided solid evidence that humans alone were the cause of great auk extinction. What we have demonstrated is that human hunting pressure was likely to have caused extinction even if the birds weren't already under threat from environmental changes."

Gilbert adds that their conclusions are limited by a couple of factors. The mitochondrial genome represents only a single genetic marker and, due to limited sample preservation and availability, the study sample size of 41 is relatively small for population genetic analyses.

"Despite these limitations, the findings help reveal how industrial-scale commercial exploitation of natural resources have the potential to drive an abundant, wide-ranging and genetically diverse species to extinction within a short period of time," says collaborator Gary Carvalho, Professor in Zoology (Molecular Ecology) at Bangor University. This echoes the conclusions of a previous study* on the passenger pigeon, a bird that existed in significant numbers before going extinct in the early 20th century.

"Our work also emphasises the need to thoroughly monitor commercially harvested species, particularly in poorly researched environments such as our oceans," concludes co-senior author Michael Knapp, Senior Lecturer in Biological Anthropology and Rutherford Discovery Fellow at the University of Otago, New Zealand. "This will help lay the platform for sustainable ecosystems and ensure more effective conservation efforts."

Source: eLife [November 26, 2019]

Extra-terrestrial impacts may have triggered 'bursts' of plate tectonics

By: Thomas Schmitt Attorney on November 26, 2019 / comment : 0 Earth Science, Geology, Palaeontology

When - and how - Earth's surface evolved from a hot, primordial mush into a rocky planet continually resurfaced by plate tectonics remain some of the biggest unanswered questions in earth science research. Now a new study, published in Geology, suggests this earthly transition may in fact have been triggered by extra-terrestrial impacts.

Spherules in the Barberton greenstone belt in the Kaapvaal craton, South Africa [Credit: Lowe et al., 2014]

"We tend to think of the Earth as an isolated system, where only internal processes matter," says Craig O'Neill, director of Macquarie University's Planetary Research Centre. "Increasingly, though, we're seeing the effect of solar system dynamics on how the Earth behaves."

Modelling simulations and comparisons with lunar impact studies have revealed that following Earth's accretion about 4.6 billion years ago, Earth-shattering impacts continued to shape the planet for hundreds of millions of years. Although these events appear to have tapered off over time, spherule beds -- distinctive layers of round particles condensed from rock vaporized during an extra-terrestrial impact -- found in South Africa and Australia suggest the Earth experienced a period of intense bombardment about 3.2 billion years ago, roughly the same time the first indications of plate tectonics appear in the rock record.

This coincidence caused O'Neill and co-authors Simone Marchi, William Bottke, and Roger Fu to wonder whether these circumstances could be related. "Modelling studies of the earliest Earth suggest that very large impacts - more than 300 km in diameter - could generate a significant thermal anomaly in the mantle," says O'Neill. This appears to have altered the mantle's buoyancy enough to create upwellings that, according to O'Neill, "could directly drive tectonics."

But the sparse evidence found to date from the Archaean - the period of time spanning 4.0 to 2.5 billion years ago - suggests that mostly smaller impacts less than 100 km in diameter occurred during this interval. To determine whether these more modest collisions were still large and frequent enough to initiate global tectonics, the researchers used existing techniques to expand the Middle Archaean impact record and then developed numerical simulations to model the thermal effects of these impacts on Earth's mantle.

The results indicate that during the Middle Archaean, 100-kilometer-wide impacts (about 30 km wider than the much younger Chixculub crater) were capable of weakening Earth's rigid, outermost layer. This, says O'Neill, could have acted as a trigger for tectonic processes, especially if Earth's exterior was already "primed" for subduction.

"If the lithosphere were the same thickness everywhere, such impacts would have little effect," states O'Neill. But during the Middle Archean, he says, the planet had cooled enough for the mantle to thicken in some spots and thin in others. The modelling showed that if an impact were to happen in an area where these differences existed, it would create a point of weakness in a system that already had a large contrast in buoyancy - and ultimately trigger modern tectonic processes.

"Our work shows there is a physical link between impact history and tectonic response at around the time when plate tectonics was suggested to have started," says O'Neill. "Processes that are fairly marginal today - such as impacting, or, to a lesser extent, volcanism - actively drove tectonic systems on the early Earth," he says. "By examining the implications of these processes, we can start exploring how the modern habitable Earth came to be."

Source: Geological Society of America [November 26, 2019]

Dinosaur skull turns paleontology assumptions on their head

By: Thomas Schmitt Attorney on November 25, 2019 / comment : 0 Dinosaurs, Fossils, North America, Palaeontology

A team of researchers at the University of Alberta has unearthed a well-preserved Styracosaurus skull--and its facial imperfections have implications for how paleontologists identify new species of dinosaurs.

Styracosaurus skull [Credit: Pixabay]

The skull was discovered by Scott Persons in 2015, then a graduate student in the Department of Biological Sciences, during an expedition in the badlands northwest of Dinosaur Provincial Park.

Nicknamed Hannah, the dinosaur was a Styracosaurus - a horned dinosaur over five metres in length with a fan of long horns. UAlberta paleontologists led by Robert Holmes, professor in the Department of Biological Sciences, have learned much from those horns--because they aren't symmetrical.

"When parts of one side of the skull were missing, paleontologists have assumed that the missing side was symmetrical to the one that was preserved," explained Persons. "Turns out, it isn't necessarily. Today, deer often have left and right antlers that are different in terms of their branching patterns. Hannah shows dramatically that dinosaurs could be the same way."

Hannah's skull, seen from all sides. The jacket used to recover Hannah’s skull weighed 2500 kilograms—requiring a helicopter to retrieve from the field! [Credit: Scott Persons]

The differences in the skull's left and right halves are so extreme that had the paleontologists found only isolated halves, they might have concluded that they belong to two different species

"The skull shows how much morphological variability there was in the genus," said Holmes. Like the antlers of modern deer and moose, Hannah shows that the pattern of dinosaur horns could vary significantly--meaning some fossils that were once assumed to be unique species will have to be reevaluated.

Tradition dictates that the person who finds an important dinosaur specimen gets to give it a nickname. "Hannah the dinosaur is named after my dog," explained Persons, now a professor and museum curator at the College of Charleston. "She's a good dog, and I knew she was home missing me while I was away on the expedition."

Paleontologist Scott Persons, pictured alongside the partially-uncovered skull. The Styracosaurus skull has implications for how horned dinosaurs are identified [Credit: Scott Persons]

Despite the nickname, paleontologists have no way of knowing if the dinosaur was female. But they have learned other details from the skull--from a partnership with researchers in the Faculty of Engineering.

"Ahmed Qureshi and graduate student Baltej Rupal in the Faculty of Engineering assisted us in performing a 3D laser scan of the skull," said Persons. "That let our publication to include a digital reconstruction, allowing scientists all over the world to download the 3D model and inspect it in detail."

"This is the future of paleontological collections: digital dinosaurs."

The paper was published in Cretaceous Research.

Author: Andrew Lyle | Source: University of Alberta [November 25, 2019]

16-million-year-old fossil shows springtails hitchhiking on winged termite

By: Thomas Schmitt Attorney on November 25, 2019 / comment : 0 Dominican Republic, Fossils, Palaeontology

When trying to better the odds for survival, a major dilemma that many animals face is dispersal -- being able to pick up and leave to occupy new lands, find fresh resources and mates, and avoid intraspecies competition in times of overpopulation.

Distribution of springtails on termite and ant hosts within ~ 16 Ma old Dominican amber [Credit: N. Robin, C. D'Haese and P. Barden]

For birds, butterflies and other winged creatures, covering long distances may be as easy as the breeze they travel on. But for soil-dwellers of the crawling variety, the hurdle remains: How do they reach new, far-off habitats?

For one group of tiny arthropods called springtails (Collembola), a recent fossil discovery now suggests their answer to this question has been to piggyback on the dispersal abilities of others, literally.

In findings published in BMC Evolutionary Biology, researchers at the New Jersey Institute of Technology (NJIT) and Museum national d'Histoire naturelle have detailed the discovery of an ancient interaction preserved in 16-million-year-old amber from the Dominican Republic: 25 springtails attached to, and nearby, a large winged termite and ant from the days of the early Miocene.

The fossil exhibits a number of springtails still attached to the wings and legs of their hosts, while others are preserved as if gradually floating away from their hosts within the amber. Researchers say the discovery highlights the existence of a new type of hitchhiking behavior among wingless soil-dwelling arthropods, and could be key to explaining how symphypleonan springtails successfully achieved dispersal worldwide.

Distribution of springtails on termite and ant hosts within ~ 16 Ma old Dominican amber, and illustration of location of springtails on social insects [Credit: N. Robin, C. D’Haese and P. Barden]

"The existence of this hitchhiking behavior is especially exciting given the fact that modern springtails are rarely described as having any interspecfic association with surrounding animals," said Ninon Robin, the paper's first author whose postdoctoral research at NJIT's Department of Biological Sciences was funded by the Fulbright Program of the French-American Commission. "This finding underscores how important fossils are for telling us about unsuspected ancient ecologies as well as still ongoing behaviors that were so far simply overlooked."

Today, springtails are among the most common arthropods found in moist habitats around the world. Most springtails possess a specialized appendage under their abdomen they use to "spring" away in flee-like fashion to avoid predation. However this organ is not sufficient for traversing long distances, especially since most springtails are unable to survive long in dry areas.

The hitchhikers the researchers identified belong to a lineage of springtails found today on every continent, known as Symphypleona,which they say may have been "pre-adapted" to grasping on to other arthropods through prehensile antennae.

Because springtails would have encountered such winged termites and ants frequently due to their high abundance during the time of the preservation, these social insects may have been their preferred hosts for transportation.

Allacma fusca is a species belonging to one of the three main groups of springtails today known as Symphypleona [Credit: Urmas Tartes/Wikipedia]

"Symphypleonan springtails are unusual compared to other Collembola in that they have specialized antennae that are used in mating courtship," said Phillip Barden, assistant professor of biology at NJIT and the study's principal investigator. "This antennal anatomy may have provided an evolutionary pathway for grasping onto other arthropods. In this particular fossil, we see these specialized antennae wrapping around the wings and legs of both an ant and termite. Some winged ants and termites are known to travel significant distances, which would greatly aid in dispersal."

Barden says that the discovery joins other reports from the Caribbean and Europe of fossil springtails attached to a beetle, a mayfly and a harvestman in amber, which together suggest that this behavior may still exist today.

Barden notes that evidence of springtail hitchhiking may not have been captured in such high numbers until now due to the rarity of such a fossilized interaction, as well as the nature of modern sampling methods for insects, which typically involves submersion in ethanol for preservation.

"Because it appears that springtails reflexively detach from their hosts when in danger, evidenced by the detached individuals in the amber, ethanol would effectively erase the link between hitchhiker and host," said Barden. "Amber derives from fossilized sticky tree resin and is viscous enough that it would retain the interaction. ... Meaning, sometimes you have to turn to 16-million-year-old amber fossils to find out what might be happening in your backyard."

Author: Jesse Jenkins | Source: New Jersey Institute of Technology [November 25, 2019]

Scientists find a place on Earth where there is no life

By: Thomas Schmitt Attorney on November 22, 2019 / comment : 0 Astrobiology, Biology, Earth Science, Ethiopia, Geology, Palaeontology

Living beings, especially microorganisms, have a surprising ability to adapt to the most extreme environments on our planet, but there are still places where they cannot live. European researchers have confirmed the absence of microbial life in hot, saline, hyperacid ponds in the Dallol geothermal field in Ethiopia.

Hyperacid, hypersaline and hot ponds in the geothermal field of Dallol (Ethiopia). Despite the presence of liquid water, this multi-extreme system does not allow the development of life, according to a new study. The yellow-greenish colour is due to the presence of reduced iron [Credit: Puri Lopez-Garcia]

The infernal landscape of Dallol, located in the Ethiopian depression of Danakil, extends over a volcanic crater full of salt, where toxic gases emanate and water boils in the midst of intense hydrothermal activity. It is one of the most torrid environments on Earth. There, daily temperatures in winter can exceed 45° C and there are abundant hypersaline and hyperacid pools, with pH values that are even negative.

A recent study, published this year, pointed out that certain microorganisms can develop in this multi-extreme environment (simultaneously very hot, saline and acid), which has led its authors to present this place as an example of the limits that life can support, and even to propose it as a terrestrial analogue of early Mars.

However, now a French-Spanish team of scientists led by biologist Purificacion Lopez Garcia of the French National Centre for Scientific Research (CNRS) has published an article in Nature Ecology & Evolution that concludes otherwise. According to these researchers, there is no life in Dallol's multi-extreme ponds.

Measuring hydrothermal fluid temperature among acid gases in active chimneys [Credit: Puri Lopez-Garcia]

"After analysing many more samples than in previous works, with adequate controls so as not to contaminate them and a well-calibrated methodology, we have verified that there's no microbial life in these salty, hot and hyperacid pools or in the adjacent magnesium-rich brine lakes," stresses Lopez Garcia.

"What does exist is a great diversity of halophilic archaea (a type of primitive salt-loving microorganisms) in the desert and the saline canyons around the hydrothermal site," the biologist explains, "but neither in the hyperacid and hypersaline pools themselves, nor in the so-called Black and Yellow lakes of Dallol, where magnesium abounds. And all this despite the fact that microbial dispersion in this area, due to the wind and to human visitors, is intense."

This is confirmed by the results of all the various methods used by the team, including the massive sequencing of genetic markers to detect and classify microorganisms, microbial culture attempts, fluorescent flow cytometry to identify individual cells, chemical analysis of brines and scanning electron microscopy combined with X-ray spectroscopy.

Microbial cells (on the left) can be easily confounded with silica-rich mineral precipitates (on the right) [Credit: Puri Lopez-Garcia]

Lopez Garcia alerts that some silica-rich Dallol mineral precipitates may look like microbial cells under a microscope, so what is seen must be analysed well: "In other studies, apart from the possible contamination of samples with archaea from adjacent lands, these mineral particles may have been interpreted as fossilized cells, when in reality they form spontaneously in the brines even though there is no life."

According to the authors, this work "helps to circumscribe the limits of habitability and demands caution when interpreting morphological bio-signatures on Earth and beyond," that is, one should not rely on the apparently cellular or 'biological' aspect of a structure, because it could have an abiotic origin.

"In addition, our study presents evidence that there are places on the Earth's surface, such as the Dallol pools, which are sterile even though they contain liquid water," stresses Lopez Garcia. This means that the presence of liquid water on a planet, which is often used as a habitability criterion, does not directly imply that it has life.

Colourful hyperacid and hypersline hydrothermal ponds at the geothermal field of Dallol [Credit: Puri Lopez-Garcia]

In this case, the researchers have found two physical-chemical barriers that prevent the presence of living organisms in ponds: the abundance of chaotropic magnesium salts (an agent that breaks hydrogen bridges and denatures biomolecules) and the simultaneous confluence of hypersaline, hyperacid and high-temperature conditions.

"We would not expect to find life forms in similar environments on other planets, at least not based on a biochemistry similar to terrestrial biochemistry," points out Lopez Garcia, who insists on the need to have multiple indications, to analyse all types of alternatives and to be very prudent with interpretations before reaching any conclusions in astrobiology.

Both the French-Spanish group, in which researchers from the Geological and Mining Institute of Spain and the Autonomous University of Madrid participate, and other international teams continue to investigate the extreme environment of Dallol, where completely sterile pools could alternate with others with slightly better biophysical conditions that allow the presence of archaea and other extremophilic microorganisms. In any case, this is an exceptional environment to continue studying the limits of life.

Source: Plataforma SINC [November 22, 2019]

Two million-year-old ice cores provide first direct observations of an ancient climate

By: Thomas Schmitt Attorney on November 21, 2019 / comment : 0 Antarctic, Climate Change, Earth Science, Palaeoclimate, Palaeontology

Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica that provide the first direct observations of Earth's climate at a time when the furred early ancestors of modern humans still roamed.

Princeton University-led researchers have extracted 2 million-year-old ice cores from Antarctica -- the oldest yet recovered -- that provide the first direct observations of prehistoric atmospheric conditions and temperatures. They used data from the ice cores to answer long-held questions about how our current colder, longer glacial cycle emerged [Credit: Sean Mackay, Boston University]

Gas bubbles trapped in the cores -- which are the oldest yet recovered -- contain pristine samples of carbon dioxide, methane and other gases that serve as "snapshots" of prehistoric atmospheric conditions and temperatures, the researchers recently reported in the journal Nature. The cores were collected in the remote Allan Hills of Antarctica.

First author Yuzhen Yan, who received his Ph.D. in geosciences from Princeton in 2019, explained that because ice flows and compresses over time, continual ice cores only extend back to 800,000 years ago. The cores he and his co-authors retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot.

"You don't get a sense of how things changed continually, but you get an idea of big changes over time," said Yan, whose graduate research on ice cores supported by a 2016 Walbridge Fund Graduate Award for Environmental Research from the Princeton Environmental Institute (PEI) was a basis for the current work.

The ice cores reported in Nature are the latest to come out of the research group of senior author John Higgins, a Princeton associate professor of geosciences, PEI associated faculty and Yan's doctoral co-adviser. A previous team led by Higgins recovered a 1 million-year-old ice core from the Allan Hills, which was the oldest ice core ever recorded by scientists when it was reported in the journal Proceedings of the National Academy of Sciences in 2015. The cores were dated by measuring isotopes of the gas argon trapped in bubbles in the ice, a technique developed by co-author Michael Bender, Princeton professor of geosciences, emeritus, and PEI associated faculty.

Gas bubbles trapped in the cores contain pristine samples of carbon dioxide, methane and other gases that serve  as 'snapshots' of the ancient climate. Because ice flows and compresses over time, the cores the researchers retrieved are like scenes collected from a very long movie that do not show the whole film, but convey the overall plot [Credit: Sean Mackay, Boston University]

"The ability to measure atmospheric composition directly is one of the biggest advantages of ice cores," Yan said. "That's why people spend years and years in the most isolated places getting them."

In the latest publication, the researchers use data from the ice cores to answer long-held questions about how our current glacial cycle emerged. Up until roughly 1.2 million years ago, Earth's ice ages consisted of thinner, smaller glaciers that came and went every 40,000 years on average.

Then, after what is known as the Mid-Pleistocene Transition, there emerged our current world characterized by colder and longer glacial cycles of 100,000 years. The two periods are known as the 40k and 100k world, respectively.

Some existing theories have stated that the 100k world -- which includes the last ice age that ended 11,700 years ago -- came about because of a long-term decline in atmospheric carbon dioxide, Yan said. But the researchers found that this was not the case -- average carbon dioxide was relatively steady through the 40k and 100k worlds. While the lowest temperatures and carbon dioxide levels of the 40k world were greater than the low points of the 100k world, the highest levels of both ages were similar.

"It could be the case that after the Mid-Pleistocene Transition, something occurred that lowered global glacial temperatures and atmospheric carbon dioxide values," Yan said. "This is the first time we have direct access to these greenhouse gas measurements. The ice core also opens up an array of new measurement possibilities that can give us insights into the 40k world when glacial cycles were very different from what we have today."

The researchers collected the 2 million-year-old ice cores in the remote Allan Hills, where high winds help create  the environmental conditions that draw ancient ice toward the surface. They found that although a long-term decline in atmospheric carbon dioxide did not directly lead to today's colder glacial cycle, temperature and global ice volume nonetheless tracked carbon dioxide closely [Credit: Sean Mackay, Boston University]

Although a long-term decline in average atmospheric carbon dioxide may not have directly led to the 100k world, the researchers nonetheless observed a correlation between carbon dioxide and global temperature, Bender said.

"To say that carbon dioxide is not a factor would be completely wrong," Bender said. "During the 40,000- and 100,0000-year glacial-interglacial cycles, temperature and global ice volume tracks carbon dioxide rather closely. Carbon dioxide changes are required to get from the cooler glacial temperatures to the warmer interglacial temperatures."

The amount of carbon dioxide now in the atmosphere tops 400 parts-per-million (ppm), which is nearly 100 ppm higher than the highest levels of the 40k world, Yan said.

"We're seeing carbon dioxide levels not seen in 2 million years," Yan said. "While our data suggest that long-term carbon dioxide decline was not the decisive factor in the Mid-Pleistocene Transition, it does not mean that carbon dioxide does not have the capability to bring about global-scale changes.

"We're in a different situation now -- carbon dioxide is the major player in our current world," he said. "If we want to look into the geologic past for an analogy of what's going on in our world today, we need to go beyond 2 million years to find it."

Author: Morgan Kelly | Source: Princeton University [November 21, 2019]

New fossils shed light on how snakes got their bite and lost their legs

By: Thomas Schmitt Attorney on November 20, 2019 / comment : 0 Australia, Fossils, Palaeontology, South America

New fossils of an ancient legged snake, called Najash, shed light on the origin of the slithering reptiles.

Lifelike rendition of Najash [Credit: Raul O. Gomez, Universidad de Buenos Aires]

The fossil discoveries published in Science Advances have revealed they possessed hind legs during the first 70 million years of their evolution. They also provide details about how the flexible skull of snakes evolved from their lizard ancestors.

The evolution of the snake body has captivated researchers for a long time - representing one of the most dramatic examples of the vertebrate body's ability to adapt - but a limited fossil record has obscured our understanding of their early evolution until now.

Dr Alessandro Palci, from Flinders University, was part of the international research team that performed high-resolution (CT) scanning and light microscopy of the preserved skulls of Najash to reveal substantial new anatomical data on the early evolution of snakes.

Najash specimens from LBPA [Credit: Garberoglio et al. 2019]

"Snakes are famously legless, but then so are many lizards. What truly sets snakes apart is their highly mobile skull, which allows them to swallow large prey items. For a long time we have been lacking detailed information about the transition from the relatively rigid skull of a lizard to the super flexible skull of snakes".

"Najash has the most complete, three-dimensionally preserved skull of any ancient snake, and this is providing an amazing amount of new information on how the head of snakes evolved. It has some, but not all of the flexible joints found in the skull of modern snakes. Its middle ear is intermediate between that of lizards and living snakes, and unlike all living snakes it retains a well-developed cheekbone, which again is reminiscent of that of lizards."

Flinders University and South Australian Museum researcher Professor Mike Lee, was also part of the study, and adds "Najash shows how snakes evolved from lizards in incremental evolutionary steps, just like Darwin predicted."

CT scan reconstructions of the articulated skull of Najash [Credit: Garberoglio et al. 2019]

The new snake family tree also reveals that snakes possessed small but perfectly formed hind legs for the first 70 million years of their evolution.

"These primitive snakes with little legs weren't just a transient evolutionary stage on the way to something better. Rather, they had a highly successful body plan that persisted across many millions of years, and diversified into a range of terrestrial, burowing and aquatic niches," says Professor Lee.

Source: Flinders University [November 20, 2019]

Huge tsunami hit Oman 1,000 years ago

By: Thomas Schmitt Attorney on November 19, 2019 / comment : 0 Earth Science, Geology, Middle East, Oman, Palaeontology

15-meter high waves that pushed boulders the weight of a Leopard tank inland: This is more or less how one can imagine the tsunami that hit the coast of today's Sultanate of Oman about 1,000 years ago, as concluded by a recent study by the universities of Bonn, Jena, Freiburg and RWTH Aachen. The findings also show how urgently the region needs a well-functioning early warning system. But even then, coastal residents would have a maximum of 30 minutes to get to safety in a similar catastrophe. The study will be published in the journal Marine Geology, but is already available online.

Klaus Reicherter from the University of Aachen examines a boulder that the tsunami carried onto the cliffs [Credit: Gosta Hoffmann/Uni Bonn]

Oman lies in the east of the Arabian Peninsula. The coasts of the Sultanate are repeatedly struck by tsunamis, most recently in 2013. Even with the most severe of these in recent times, the Makran event in 1945, the damage remained comparatively low. Back then, the tidal wave reached a height of three meters.

The scientists have now discovered evidence of a tsunami which is likely to have been much more powerful, with waves of up to 15 meters. For this purpose, the researchers from Bonn, Jena and Aachen concentrated their terrain investigations on a 200-kilometer coastal strip in northeastern Oman. "There we identified 41 large boulders, which were apparently carried inland by the force of the water," explains Dr. Gösta Hoffmann from the Institute for Geosciences at the University of Bonn.

Quartz clock in the rock

Some of the boulders were probably formed when the tsunami shattered parts of the cliffs; for one of them, the largest weighing around 100 metric tons, scientists were even able to determine the exact point at which it broke off. Others show traces of marine organisms such as mussels or oysters that cannot survive on land. "Certain methods can be used to determine their time of death," says the geologist Gösta Hoffmann. "This allowed us to establish when the boulders were washed ashore."

The quartz crystals in the rock also represent a kind of clock: They provide information about the last time they were exposed to the sun. This allowed the scientists to deduce how long the rocks had been in the place where they were found. The scientists from Freiburg are specialists in this method. "Many of these measurements gave us a value of about 1,000 years," emphasizes Hoffmann. "This corresponds well with the dating results of clay fragments we found in tsunami sediments. They originate from vessels used by coastal dwellers."

During sampling (from the left): Christoph Grutzner (University of Jena); Benjamin Koster, Klaus Reicherter and Sascha Schneiderwind (all University of Aachen) [Credit: Gosta Hoffmann/Uni Bonn]

The Arabian and Eurasian tectonic plates collide in the Arabian Sea. They move towards each other at a speed of about four centimeters per year. During this process, one plate slides beneath the other. Sometimes they get stuck in this subduction zone. This can cause tensions that intensify more and more over years and decades. If they suddenly come loose with a violent jolt, the water column above the plates starts to move. This can lead to the extremely destructive waves that are characteristic of tsunamis.

"So far it has been unclear to what extent the Arabian and Eurasian plates get stuck," says Hoffmann. At the Makran event of 1945, for example, the effects were locally confined. The current findings, however, suggest that the tensions can also build up and unload on a very large scale - there is no other feasible explanation for the enormous forces at work at the time. "It is therefore extremely important that a tsunami early warning system is put in place for this region," stresses the geologist.

Nevertheless, even a smaller tsunami would have devastating consequences today: A large part of the vital infrastructure in the Sultanate of Oman has been built near the coast, such as the oil refineries and seawater desalination plants. A well-functioning warning system can, however, at least give residents some time to get to safety. Not very much though: Tsunamis move at the speed of a passenger aircraft; in the best case, the time between the alarm and the wave's impact would therefore be little more than 30 minutes.

Source: University of Bonn [November 19, 2019]

New finding on origin of avian predentary in Mesozoic birds

By: Thomas Schmitt Attorney on November 18, 2019 / comment : 0 China, Early Birds, Fossils, Palaeontology

The predentary bone is one of the most enigmatic skeletal elements in avian evolution. Located at the tip of the lower jaw, this bone is absent in more primitive birds and in living birds; it is thought to have been lost during evolution. For over 30 years, the origin and function of the avian predentary has remained mysterious.

This is a reconstruction of Yanornis martini feeding on fish along a shallow  lakeshore of the Jehol biota [Credit: Michael Rothman]

Now, however, Alida Bailleul, LI Zhiheng, Jingmai O'Connor and ZHOU Zhonghe from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences have made significant progress towards solving this long-standing mystery. Their findings were published in Proceedings of the National Academy of Sciences.

Using a battery of analytical methods, the team, led by Dr. Bailleul, presents strong evidence that the avian predentary was covered by a keratinous beak - a horny sheath that covers the bones of the rostrum in all living birds, all of which are edentulous and have beaks. It also provides evidence the predentary was proprioceptive, i.e., it was able to detect external mechanical stimuli; and was mobile - thus representing a now extinct form of cranial kinesis.

Cranial kinesis occurs when joints are able to move within the skull - mainly between the upper jaw and the braincase. This feature is widespread in living birds; however, it is thought to be mostly absent in Mesozoic birds.

Based on her examination of the fossilized tissues of the predentary and other jaw elements of Yanornis martini from the Jehol Biota, Dr. Bailleul identified a specific type of cartilage inside the joint between the predentary and dentary that strongly suggests some movement between these elements.

The pink arrow points to the predentary and the blue arrow points to the upper portion of the jaw, which has no teeth. Together, they may have been covered by a keratinous beak, and the predentary was most likely mobile [Credit: IVPP]

The team noticed that the predentary is only found in ornithuromorphs that have teeth. However, the tip of the premaxilla - the bone of the upper bill that would have occluded with the predentary - is without teeth. This suggests that the tip of the upper jaw, like the predentary, was also covered with a keratinous beak.

The tiny beak at the tip of the skull, combined with the sensitive and mobile predentary bone and teeth that were most likely also proprioceptive, represents a unique feeding adaptation that allowed greater dexterity when manipulating food. Although bizarre and now extinct, this unique feeding apparatus persisted in the ornithuromorph clade for at least 58 million years, from the Early to the Late Cretaceous.

Using information from the fossilized tissues and preexisting data on the embryology of living birds, the team also formulated a hypothesis regarding the origin of this bone, suggesting it is a sesamoid, similar to the human knee cap. Identification as a sesamoid means this bone is a novel skeletal innovation unique to one lineage of ornithuromorphs, and that it did not arise from a preexisting skull bone.

Although additional research on fossils birds (and also extant birds) is required to confirm some of these hypotheses, the predentary is such a small bone that it is only rarely preserved, thus making it very difficult - if not impossible - to find specimens that can shed light on the remaining pieces of this mystery.

Source: Chinese Academy of Sciences [November 18, 2019]