Wasous

About 2.6 million years ago, an oddly bright light arrived in the prehistoric sky and lingered there for weeks or months. It was a supernova some 150 light years away from Earth. Within a few hundred years, long after the strange light in the sky had dwindled, a tsunami of cosmic energy from that same shattering star explosion could have reached our planet and pummeled the atmosphere, touching off climate change and triggering mass extinctions of large ocean animals, including a shark species that was the size of a school bus.

A nearby supernova remnant [Credit: NASA]

The effects of such a supernova -- and possibly more than one -- on large ocean life are detailed in a paper just published in Astrobiology.

"I've been doing research like this for about 15 years, and always in the past it's been based on what we know generally about the universe -- that these supernovae should have affected Earth at some time or another," said lead author Adrian Melott, professor emeritus of physics & astronomy at the University of Kansas. "This time, it's different. We have evidence of nearby events at a specific time. We know about how far away they were, so we can actually compute how that would have affected the Earth and compare it to what we know about what happened at that time -- it's much more specific."

Melott said recent papers revealing ancient seabed deposits of iron-60 isotopes provided the "slam-dunk" evidence of the timing and distance of supernovae.

"As far back as the mid-1990s, people said, 'Hey, look for iron-60. It's a telltale because there's no other way for it to get to Earth but from a supernova.' Because iron-60 is radioactive, if it was formed with the Earth it would be long gone by now. So, it had to have been rained down on us. There's some debate about whether there was only one supernova really nearby or a whole chain of them. I kind of favor a combo of the two -- a big chain with one that was unusually powerful and close. If you look at iron-60 residue, there's a huge spike 2.6 million years ago, but there's excess scattered clear back 10 million years."

Melott's co-authors were Franciole Marinho of Universidade Federal de Sao Carlos in Brazil and Laura Paulucci of Universidade Federal do ABC, also in Brazil.

According to the team, other evidence for a series of supernovae is found in the very architecture of the local universe.

"We have the Local Bubble in the interstellar medium," Melott said. "We're right on its edge. It's a giant region about 300 light years long. It's basically very hot, very low-density gas -- nearly all the gas clouds have been swept out of it. The best way to manufacture a bubble like that is a whole bunch of supernovae blows it bigger and bigger, and that seems to fit well with idea of a chain. When we do calculations, they're based on the idea that one supernova that goes off, and its energy sweeps by Earth, and it's over. But with the Local Bubble, the cosmic rays kind of bounce off the sides, and the cosmic-ray bath would last 10,000 to 100,000 years. This way, you could imagine a whole series of these things feeding more and more cosmic rays into the Local Bubble and giving us cosmic rays for millions of years."

Muons showering Earth may have spelled curtains for Megalodon, a school-bus-sized shark, 2.6 million years ago [Credit: Karen Carr]

Whether or not there was one supernova or a series of them, the supernova energy that spread layers of iron-60 all over the world also caused penetrating particles called muons to shower Earth, causing cancers and mutations -- especially to larger animals.

"The best description of a muon would be a very heavy electron - but a muon is a couple hundred times more massive than an electron," Melott said. "They're very penetrating. Even normally, there are lots of them passing through us. Nearly all of them pass through harmlessly, yet about one-fifth of our radiation dose comes by muons. But when this wave of cosmic rays hits, multiply those muons by a few hundred. Only a small faction of them will interact in any way, but when the number is so large and their energy so high, you get increased mutations and cancer -- these would be the main biological effects. We estimated the cancer rate would go up about 50 percent for something the size of a human -- and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up."

A supernova 2.6 million years ago may be related to a marine megafaunal extinction at the Pliocene-Pleistocene boundary where 36 percent of the genera were estimated to become extinct. The extinction was concentrated in coastal waters, where larger organisms would catch a greater radiation dose from the muons.

According to the authors of the new paper, damage from muons would extend down hundreds of yards into ocean waters, becoming less severe at greater depths: "High energy muons can reach deeper in the oceans being the more relevant agent of biological damage as depth increases," they write.

Indeed, a famously large and fierce marine animal inhabiting shallower waters may have been doomed by the supernova radiation.

"One of the extinctions that happened 2.6 million years ago was Megalodon," Melott said. "Imagine the Great White Shark in 'Jaws,' which was enormous -- and that's Megalodon, but it was about the size of a school bus. They just disappeared about that time. So, we can speculate it might have something to do with the muons. Basically, the bigger the creature is the bigger the increase in radiation would have been."

The KU researcher said the evidence of a supernova, or series of them, is "another puzzle piece" to clarify the possible reasons for the Pliocene-Pleistocene boundary extinction.

"There really hasn't been any good explanation for the marine megafaunal extinction," Melott said. "This could be one. It's this paradigm change -- we know something happened and when it happened, so for the first time we can really dig in and look for things in a definite way. We now can get really definite about what the effects of radiation would be in a way that wasn't possible before."

Source: University of Kansas [December 11, 2018]

The analysis of the world’s most complete skeleton of an early human ancestor, conducted by a research collaboration involving the University of Liverpool, offers conclusive evidence that human ancestors became efficient upright walkers while they were still substantially tree dwelling animals.

Professor Ronald Clarke with Little Foot [Credit: University of Liverpool]

The first bones of the 3.67 million old skeleton, specimen StW 573 nicknamed ‘Little Foot’, were 12 foot bones and leg bone fragments identified in boxes in the 1990s. The rest of the skeleton has undergone two decades of painstaking excavation, cleaning, restoring and analysis. It was found in a very deep cavern, with the bone embedded in a concrete-like matrix. The bone is very delicate and in some cases literally paper-thin. However, it has given scientists a far greater understanding of how our species evolved.

Limbs intact

The over 90% complete skeleton of an old female, much more than twice as complete as the famous Lucy, and considerably older as well, Little Foot is a member of the genus Australopithecus, a widespread and varied genus of hominins to which Lucy belonged, and which was an early precursor to modern-day Homo sapiens which appeared roughly 300,000 years ago. Little Foot is the first fossil of Australopithecus ever to have been discovered with its limbs intact.

Little Foot’s fossil bones [Credit: Patrick Landmann/Science Photo Library]

The studies support the argument of her discoverer, Professor Ronald Clarke of the University of the Witwatersrand, that there were two species of Australopithecus living at the same time in South Africa’s ‘Cradle of Humankind’, Australopithecus africanus, which was small, like Lucy, and probably primarily tree-dwelling, and Australopithecus prometheus, which was probably just within the range of modern human stature.

Important finding

As part of the study, which has been reported in Nature Science, Professor Robin Crompton, Honorary University of Liverpool Research Associate in Musculoskeletal Biology, and his colleagues analysed how she would have walked.


Professor Crompton, states: “This hominin, for the first time in the fossil record, had longer lower limbs than upper limbs, like ourselves. This is an important finding, as the slightly older hominin Ardipithecus, which came before Australopithecus, had longer arms than legs – more like other great apes such as the gorilla.

“That means she was being selected for long stride length in bipedalism. Moreover, unlike Lucy, ‘Littlefoot’ had a hip joint like our own, able to transmit large forces from the trunk to the leg and vice versa. Although Little Foot’s legs were longer than her arms, they had not yet achieved the great relative leg length found in humans. Thus, she would not have been as good at carrying objects as we are. However, she would have been much better at climbing trees than modern humans.

“It is most likely that she would have resided in an area that was a mix of tropical rainforest, broken woodland and grassland, through which she would roam around. She would have lived primarily on forest fruits and leaves”

Source: University of Liverpool [December 10, 2018]

Our future on Earth may also be our past. In a study published in the Proceedings of the National Academy of Sciences, researchers show that humans are reversing a long-term cooling trend tracing back at least 50 million years. And it's taken just two centuries.

Epihippus gracilis, one of the many early horses found in the Hancock Mammal Quarry in Oregon, depicted around 30 million years ago. Their ancestors would have gotten their start in the Eocene [Credit: National Park Services]

By 2030, Earth's climate is expected to resemble that of the mid-Pliocene, going back more than 3 million years in geologic time. Without reductions in our greenhouse gas emissions, our climates by 2150 could compare to the warm and mostly ice-free Eocene, an epoch that characterized the globe 50 million years ago.

"If we think about the future in terms of the past, where we are going is uncharted territory for human society," says the study's lead author, Kevin Burke, who conducted the work while a graduate student in the lab of paleoecologist John "Jack" Williams, professor of geography at the University of Wisconsin-Madison. "We are moving toward very dramatic changes over an extremely rapid time frame, reversing a planetary cooling trend in a matter of centuries."

All of the species on Earth today had an ancestor that survived the Eocene and the Pliocene, but whether humans and the flora and fauna we are familiar with can adapt to these rapid changes remains to be seen. The accelerated rate of change appears to be faster than anything life on the planet has experienced before.

The new study builds upon work Williams and colleagues first published in 2007, which compared future climate projections to historical climate data from the early 20th century. The new study relies on extensive data about climate conditions to probe much deeper in Earth's geologic past and expand those comparisons.

"We can use the past as a yardstick to understand the future, which is so different from anything we have experienced in our lifetimes," says Williams. "People have a hard time projecting what the world will be like five or 10 years from now. This is a tool for predicting that -- how we head down those paths, and using deep geologic analogs from Earth's history to think about changes in time."

During the Eocene, Earth's continents were packed more closely together and global temperatures averaged 23.4 degrees Fahrenheit (13 degrees Celsius) warmer than they are today. Dinosaurs had recently gone extinct and the first mammals, like ancestral whales and horses, were spreading across the globe. The Arctic was occupied by swampy forests like those found today in the southern U.S.

Future climate analogs for the years 2020, 2050, 2100 and 2200 according to three well-established models. If greenhouse gas emissions are not curbed, the study says, the climate will continue to warm until it begins to resemble the Eocene in 2100 [Credit: Burke et al. 2018]

In the Pliocene, North and South America joined tectonically, the climate was arid, land bridges allowed animals to spread across continents and the Himalayas formed. Temperatures were between 3.2 and 6.5 degrees Fahrenheit (1.8 to 3.6 degrees Celsius) warmer than they are today.

For the study, Burke and Williams -- along with colleagues at the University of Bristol, Columbia University, University of Leeds, NASA Goddard Institute for Space Studies and the National Center for Atmospheric Research -- examined the similarities between future climate projections as set forth by the Intergovernmental Panel on Climate Change Fifth Assessment Report and several periods of geologic history.

These included the Early Eocene, the mid-Pliocene, the Last Interglacial (129 to 116 thousand years ago), the mid-Holocene (6,000 years ago), the pre-industrial era (before A.D. 1850) and the early 20th century.

They used Representative Concentration Pathway 8.5 (RCP8.5), which represents a future climate scenario in which we do not mitigate greenhouse gas emissions, and RCP4.5, a scenario in which we moderately reduce greenhouse gas emissions, and climate simulations using three different but well-established models: the Hadley Centre Coupled Model version 3, the Goddard Institute for Space Studies ModelE2-R and the Community Climate System Model.

While not without their flaws, each of these models represents the best available data and state-of-the-art techniques.

Under both scenarios and across each model, compared to previous eras, the Earth's climate most closely resembled the mid-Pliocene by 2030 (under RCP8.5) or 2040 (under RCP4.5). Under the greenhouse gas stabilization scenario of RCP4.5, the climate then stabilizes at mid-Pliocene-like conditions, but under the higher greenhouse gas emissions of RCP8.5, the climate continues to warm until it begins to resemble the Eocene in 2100, achieving Eocene-like conditions more broadly by 2150.

The models showed these deep-geological climates emerging first from the center of continents and then expanding outward over time. Temperatures rise, precipitation increases, ice caps melt and climates become temperate near the Earth's poles.

"Madison (Wisconsin) warms up more than Seattle (Washington) does, even though they're at the same latitude," Williams explains. "When you read that the world is expected to warm by 3 degrees Celsius this century, in Madison we should expect to roughly double the global average."


The study also showed that under RCP8.5, "novel" climates emerge across nearly 9 percent of the planet. These are conditions that do not have known geologic or historical precedent and they concentrate in eastern and southeastern Asia, northern Australia and the coastal Americas.

"Based on observational data, we are tracking on the high end of the emissions scenarios, but it's too soon to tell," says Burke. "We may be somewhere between RCP4.5 and RCP8.5, though if we increase our climate mitigation efforts -- like switching to renewable energy -- we could find ourselves closer to the low end."

About a decade ago, Swedish scientist Johan Rockström and colleagues introduced the idea of "safe operating space," referring to the climate conditions under which modern agricultural societies developed. By comparing to the deep past, Williams and Burke say, we are able to better understand the planetary boundaries and thresholds that delineate this space.

"The further we move from the Holocene, the greater the potential that we move out of safe operating space," says Williams, a faculty affiliate with the UW-Madison Nelson Institute Center for Climatic Research. "In the roughly 20 to 25 years I have been working in the field, we have gone from expecting climate change to happen, to detecting the effects, and now, we are seeing that it's causing harm. People are dying, property is being damaged, we're seeing intensified fires and intensified storms that can be attributed to climate change. There is more energy in the climate system, leading to more intense events."

In their paper, the researchers try to strike a balance between alarm and optimism. On the one hand, Earth is headed into the unknown in our children's and grandchildren's lifetimes. On the other, life has long proven to be resilient. And, Williams says, in many places we are moving away from fossil fuels toward more sustainable and carbon-free energy sources. But more needs to be done.

"We've seen big things happen in Earth's history -- new species evolved, life persists and species survive. But many species will be lost, and we live on this planet," says Williams. "These are things to be concerned about, so this work points us to how we can use our history and Earth's history to understand changes today and how we can best adapt."

Author: Kelly April Tyrrell | Source: University of Wisconsin-Madison [December 10, 2018]

Iridescence is responsible for some of the most striking visual displays in the animal kingdom. Now, thanks to a new study of feathers from almost 100 modern bird species, scientists have gained new insights into how this colour diversity evolved.

Two of the fossils sampled for the study with the fossil melanosomes found in each fossil (scanning electron microscope images). Scaniacypselus to the left and Primotrogon to the right. Melanosome shape varies in the different samples, and is indicative of colour. The sample furthest to the left was predicted as iridescent [Credit: Jakob Vinther & Fiann Smithwick]

Iridescence refers to the phenomena where colour changes when an object is viewed from different angles. Birds produce this varying coloration in their feathers by using nanoscale arrays of melanin-filled organelles (melanosomes) layered with keratin. In this form of structural colouration, the shapes of melanosomes together with the thickness of keratin layers determine what colour is produced.

While melanosome morphology has previously been used to predict colour in fossil animals, melanosome variation in iridescent feathers has not been analysed on as large a scale until this study.

As reported in the journal Evolution, a team of University of Bristol researchers used scanning electron microscopy to quantify melanosome extracts from the feathers of 97 species of modern birds with iridescent plumage, taken from the collections of the Zoological Museum of Copenhagen.

The study showed that iridescent feathers contain the most varied melanosome morphologies of all types of bird coloration sampled to date. Unlike black, grey and brown feathers that always contain solid melanosomes, iridescent feathers can contain melanosomes that are hollow and/or flattened.

Scaniacypselus fossil (above) compared with its modern day equivalent, the Plume-toed Swiftlet [Credit: Fossil: Jakob Vinther & Fiann Smithwick/Daniel Field]

"We found that melanosomes in modern iridescent feathers are more diverse in shape than those found in grey, black or brown feathers combined (that also contain melanosomes)," said lead author Klara Nordén, who conducted the study during her undergraduate years at Bristol's School of Earth Sciences. "It is already known that structural colouration is responsible for 70 per cent of the colour variability in birds. These two facts might be coupled -- birds evolved varied forms of melanosomes to achieve ever greater diversity in colour.

"I wanted to find out if we could improve current predictive models for fossil colour based on melanosome morphology by including all types of melanosomes found in iridescent feathers."

Dr Jakob Vinther, co-author of the study and a leading researcher in the field of paleocolour at Bristol's School of Biological Sciences, had already collected the perfect fossil samples to test the new model on.

"We had sampled Scaniacypselus, related to modern tree swifts, and Primotrogon, ancestor to modern trogons. These groups are iridescent today and have flat and hollow melanosomes. Did their 48-million-year-old ancestors from Germany also have iridescent plumage?"

Primotrogon fossil (above) compared with its modern day equivalent, the Narina Trogon [Credit: Fossil: Jakob Vinther & Fiann Smithwick/Daniel Field]

Interestingly, the model predicted that Primotrogon probably was iridescent, but it used solid rather than hollow melanosomes, unlike its modern descendants.

"This demonstrates how we now have the tools to map out the evolution of iridescence in fossil lineages," said Klara, who is now a PhD student at Princeton University. "It opens the door to many new discoveries of dazzling displays in fossil birds and other dinosaurs."

The current study focused on mapping out how melanosomes vary in iridescent feathers. Further avenues of research might examine why birds utilise such diversity of melanosome types in iridescent feathers. These insights could ultimately enhance our understanding of why fossil birds or dinosaurs might have used such morphologies, revealing something about their behaviour.

Source: University of Bristol [December 10, 2018]

A QUT-led collaboration with University of Adelaide reveals that Australia's pint-sized banded hare-wallaby is the closest living relative of the giant short-faced kangaroos which roamed the continent for millions of years, but died out about 40,000 years ago.

The diminutive banded hare-wallaby linked to the giant Sthenurinae kangaroos [Credit: Queensland University of Technology]

Published in Systematic Biology, the research involved the first near-complete mitochondrial (mt) genome sequencing from extinct Australian megafauna.

- DNA was sequenced from inner ear bones (petrous bones) of a 45,000-year-old giant short-faced kangaroo, Simosthenurus occidentalis, part of the Sthenurinae sub-family, found at Mt Cripps in Tasmania

- These are the longest DNA sequences ever recovered from Australia's extinct megafauna, with more than 16,000 base pairs of mtDNA, which is used to help understand evolutionary relationships

- The results support an evolutionary link between giant short-faced kangaroos (Sthenurinae) and the threatened banded hare-wallaby, Lagostrophus fasciatus

- The study also combined the DNA evidence with fossil and anatomical data to trace body size change over the evolutionary history of kangaroos and wallabies

The analysis was conducted by QUT evolutionary biologists Ph.D. researcher Manuela Cascini and Associate Professor Matthew Phillips, from the Science and Engineering Faculty, in collaboration with University of Adelaide's Professor Alan Cooper and Dr. Kieren Mitchell, who undertook the DNA sequencing at the Australian Centre for Ancient DNA.

Credit: Queensland University of Technology

Lead author Ms Cascini, a molecular biologist who moved from Italy to undertake her Ph.D. research with Associate Professor Phillips, said her project also involved analysis of mtDNA sequenced from the inner ear bones of another ancient extinct macropod that was found in Tasmania – the giant wallaby, Protemnodon anak, which weighed up to 150 kilograms.

Small fragments of ancient DNA sequenced from this giant wallaby species and from the giant short-faced kangaroo were first reported on by University of Adelaide scientists in 2015.

"Our analysis confirmed their conclusion that the giant wallabies are close relatives of the iconic living Macropus genus of kangaroos and wallabies," Ms Cascini said.

"However that earlier study provided insufficient DNA to confidently place the giant short-faced kangaroos on the evolutionary tree.

"We've now been able to show the strongest evidence yet that the closest living relative of these massive Sthenurinae kangaroos, which weighed up to about 240 kilograms, is the tiny, 2-kilogram banded hare-wallaby. These wallabies live in the wild only on islands off Western Australia and are classified as vulnerable."

Largest of the extinct giant short-faced kangaroos, Procoptodon goliah, featured on an Australia Post stamp  [Credit: Queensland University of Technology]

Associate Professor Phillips said the larger amount of mtDNA sequenced in this study by the University of Adelaide collaborators helped enable the strong finding on the banded hare-wallaby link.

"This is by far the most genetic data that anyone has extracted out of Australian megafauna, and it was taken from the petrous bones which are denser and often seem to hold DNA better," he said.
"You find a lot of ancient DNA studies of megafauna from permafrost in northern Europe and northern America because the cold helps preserve the DNA. But in Australia the hotter climate and older age of the megafauna is far less favourable for DNA preservation."

Dr. Mitchell said Tasmania's cooler climate and higher-altitude caves "make for much better DNA preservation than we find elsewhere in Australia, so we focused our hunt for high-quality megafaunal DNA there".

Associate Professor Phillips said other findings of the study on the evolution of kangaroos and wallabies (macropods) included:

- The macropod ancestors diverged from tree-living possums around 41 to 46 million years ago

- They remained small, in the 2-15 kg range, while Australia was more dominated by rainforest

- As the climate cooled and dried, and as the forests opened up over the past 10 million years, at least four different kangaroo lineages independently evolved to megafaunal size (more than 44 kg)

- This includes the short-faced kangaroos, the giant Protemnodon wallabies, and the living red and grey kangaroos.

Author: Rose Trapnell | Source: Queensland University of Technology [December 10, 2018]

The largest extinction in Earth's history marked the end of the Permian period, some 252 million years ago. Long before dinosaurs, our planet was populated with plants and animals that were mostly obliterated after a series of massive volcanic eruptions in Siberia.

This illustration shows the percentage of marine animals that went extinct at the end of the Permian era by latitude, from the model (black line) and from the fossil record (blue dots). A greater percentage of marine animals survived in the tropics than at the poles. The color of the water shows the temperature change, with red being most severe warming and yellow less warming. At the top is the supercontinent Pangaea, with massive volcanic eruptions emitting carbon dioxide. The images below the line represent some of the 96 percent of marine species that died during the event. Includes  fossil drawings by Ernst Haeckel/Wikimedia; Blue crab photo by Wendy Kaveney/Flickr; Atlantic cod photo by Hans-Petter Fjeld/Wikimedia; Chambered nautilus photo by ©2010 John White/CalPhotos [Credit: Justin Penn and Curtis Deutsch/University of Washington]

Fossils in ancient seafloor rocks display a thriving and diverse marine ecosystem, then a swath of corpses. Some 96 percent of marine species were wiped out during the "Great Dying," followed by millions of years when life had to multiply and diversify once more.

What has been debated until now is exactly what made the oceans inhospitable to life - the high acidity of the water, metal and sulfide poisoning, a complete lack of oxygen, or simply higher temperatures.

New research from the University of Washington and Stanford University combines models of ocean conditions and animal metabolism with published lab data and paleoceanographic records to show that the Permian mass extinction in the oceans was caused by global warming that left animals unable to breathe. As temperatures rose and the metabolism of marine animals sped up, the warmer waters could not hold enough oxygen for them to survive.

"This is the first time that we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, which then allows us to make predictions about the causes of extinction in the future," said first author Justin Penn, a UW doctoral student in oceanography.

This fossilized spiraling shark tooth is from the Helicoprion, an unusual shark that lived during the Permian. The tooth whorl was located inside the shark’s lower jaw. The fossil is on display at the Idaho Museum of Natural History [Credit: James St. John/Flickr]

Researchers ran a climate model with Earth's configuration during the Permian, when the land masses were combined in the supercontinent of Pangaea. Before ongoing volcanic eruptions in Siberia created a greenhouse-gas planet, oceans had temperatures and oxygen levels similar to today's. The researchers then raised greenhouse gases in the model to the level required to make tropical ocean temperatures at the surface some 10 degrees Celsius (20 degrees Fahrenheit) higher, matching conditions at that time.

The model reproduces the resulting dramatic changes in the oceans. Oceans lost about 80 percent of their oxygen. About half the oceans' seafloor, mostly at deeper depths, became completely oxygen-free.

To analyze the effects on marine species, the researchers considered the varying oxygen and temperature sensitivities of 61 modern marine species -- including crustaceans, fish, shellfish, corals and sharks -- using published lab measurements. The tolerance of modern animals to high temperature and low oxygen is expected to be similar to Permian animals because they had evolved under similar environmental conditions. The researchers then combined the species' traits with the paleoclimate simulations to predict the geography of the extinction.

"Very few marine organisms stayed in the same habitats they were living in -- it was either flee or perish," said second author Curtis Deutsch, a UW associate professor of oceanography.

A fossil from Morocco of a Diademaproetus, one of the trilobites that were plentiful in the world’s oceans but went extinct at the end of the Permian [Credit: Géry Parent/Flickr]

The model shows the hardest hit were organisms most sensitive to oxygen found far from the tropics. Many species that lived in the tropics also went extinct in the model, but it predicts that high-latitude species, especially those with high oxygen demands, were nearly completely wiped out.

To test this prediction, co-authors Jonathan Payne and Erik Sperling at Stanford analyzed late-Permian fossil distributions from the Paleoceanography Database, a virtual archive of published fossil collections. The fossil record shows where species were before the extinction, and which were wiped out completely or restricted to a fraction of their former habitat.

The fossil record confirms that species far from the equator suffered most during the event.

"The signature of that kill mechanism, climate warming and oxygen loss, is this geographic pattern that's predicted by the model and then discovered in the fossils," Penn said. "The agreement between the two indicates this mechanism of climate warming and oxygen loss was a primary cause of the extinction."

A fossil of a Paramblypterus, a species of fish that went extinct during the Permian. This fossil is on display at the State Museum of Natural History in Karlsruhe, Germany [Credit: H. Zell/WikiCommons]

The study builds on previous work led by Deutsch showing that as oceans warm, marine animals' metabolism speeds up, meaning they require more oxygen, while warmer water holds less. That earlier study shows how warmer oceans push animals away from the tropics.

The new study combines the changing ocean conditions with various animals' metabolic needs at different temperatures. Results show that the most severe effects of oxygen deprivation are for species living near the poles.

"Since tropical organisms' metabolisms were already adapted to fairly warm, lower-oxygen conditions, they could move away from the tropics and find the same conditions somewhere else," Deutsch said. "But if an organism was adapted for a cold, oxygen-rich environment, then those conditions ceased to exist in the shallow oceans."

The so-called "dead zones" that are completely devoid of oxygen were mostly below depths where species were living, and played a smaller role in the survival rates. "At the end of the day, it turned out that the size of the dead zones really doesn't seem to be the key thing for the extinction," Deutsch said. "We often think about anoxia, the complete lack of oxygen, as the condition you need to get widespread uninhabitability. But when you look at the tolerance for low oxygen, most organisms can be excluded from seawater at oxygen levels that aren't anywhere close to anoxic."

This roughly 1.5-foot slab of rock from southern China shows the Permian-Triassic boundary. The bottom section is pre-extinction limestone. The upper section is microbial limestone deposited after the extinction [Credit: Jonathan Payne/Stanford University]

Warming leading to insufficient oxygen explains more than half of the marine diversity losses. The authors say that other changes, such as acidification or shifts in the productivity of photosynthetic organisms, likely acted as additional causes.

The situation in the late Permian -- increasing greenhouse gases in the atmosphere that create warmer temperatures on Earth -- is similar to today.

"Under a business-as-usual emissions scenarios, by 2100 warming in the upper ocean will have approached 20 percent of warming in the late Permian, and by the year 2300 it will reach between 35 and 50 percent," Penn said. "This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change."

The study is published in the journal Science.

Author: Hannah Hickey | Source: University of Washington [December 06, 2018]

Paleontologists from Russia have described a new dinosaur, the Volgatitan. Seven of its vertebrae, which had remained in the ground for about 130 million years, were found on the banks of the Volga, not far from the village of Slantsevy Rudnik, five kilometers from Ulyanovsk. The study has been published in the latest issue of Biological Communications.

Volgatitan simbirskiensis anterior caudal vertebra (holotype), in right lateral (A), anterior (B), left lateral (C), posterior (D), dorsal (E), and ventral (F) views [Credit: Alexander Averianov and Vladimir Efimov]

The Volgatitan belongs to the group of sauropods - giant herbivorous dinosaurs with a long neck and tail, who lived on Earth about 200 to 65 million years ago. Weighing around 17 tons, the ancient reptile from the banks of the Volga was not the largest among its relatives. The scientists described it from seven caudal vertebrae. The bones belonged to an adult dinosaur which is manifested by neural arches (parts of the vertebrae protecting the nerves and blood vessels), which completely merged with the bodies of the vertebrae.

The remains of the dinosaur were discovered near the village of Slantsevy Rudnik. This is where, in 1982, Vladimir Efimov discovered three large vertebrae that had fallen out of a high cliff. Later, in 1984-1987, three nodules of limestone fell off, which contained the remaining vertebrae. In his works, the head of the Undorovsky Paleontology Museum called the unusual finds "giant vertebrae of unknown taxonomic affiliation".

"In the early 1990s, Vladimir Efimov showed photographs of the bones to Lev Nesov, a well-known Leningrad paleontologist," recollected Alexander Averianov. Lev Nesov thought that the vertebrae belonged to sauropods, giant herbivorous dinosaurs. In 1997, Vladimir Efimov published a preliminary note about this find in the Paleontological Journal. He referred to the vertebrae as a sauropod of the Brachiosauridae family. Last July, I finally managed to visit him in Undory and study the bones, and also managed to determine that they belonged to the new taxon of titanosaurs."

The dinosaur received a scientific name - Volgatitan simbirskiensis. It comes from the Volga River and the city of Simbirsk (currently, Ulyanovsk). Titans are ancient Greek gods known for their large size. Therefore, according to a paleontological tradition, this word is used in many scientific names of sauropods from the group of titanosaurs. It is also part of the name of the group.

Today, along with the Volgatitan from Russia, 12 valid dinosaur taxa have already been described. There are only three sauropods among them: Tengrisaurus starkovi, Sibirotitan astrosacralis and Volgatitan simbirskiensis. The first two are the first sauropods in Russia, which were also studied by St Petersburg University scientists in 2017. According to Aleksandr Averianov, the description of dinosaur taxa in recent years has become possible due to the progress in understanding the anatomy and phylogeny of dinosaurs. In addition, the Russian sauropod allowed scientists to learn more about how these species of ancient reptiles had lived and developed.

"Previously, it was believed that the evolution of titanosaurs took place mainly in South America with some taxa moving into North America, Europe and Asia only in the Late Cretaceous," explained the St Petersburg University professor. In Asia, representatives of a broader group of titanosauriform, such as the recently described Siberian titanium, dominated in the early Cretaceous. However, the recent description of the Tengrisaurus from the Early Cretaceous of Transbaikal Region and the finding of the Volgatitan indicate that titanosaurs in the Early Cretaceous were distributed much more widely; and, perhaps, important stages of their evolution took place in Eastern Europe and Asia."

Source: Akson Russian Science Communication Association [December 06, 2018]

An ancient, dolphin-like marine reptile resembles its distant relative in more than appearance, according to an international team of researchers that includes scientists from North Carolina State University and Sweden's Lund University. Molecular and microstructural analysis of a Stenopterygius ichthyosaur from the Jurassic (180 million years ago) reveals that these animals were most likely warm-blooded, had insulating blubber and used their coloration as camouflage from predators.

Spectacular soft-tissue fossil (MH 432; Urweltmuseum Hauff, Holzmaden, Germany). Cells, cellular organelles and original  biomolecules have been discovered in preserved soft parts of an approximately 180-million-year-old ichthyosaur (literally 'fish-lizard'). Photographic (top) and diagrammatic (bottom) representation of the 85-cm-long fossil (which corresponds to roughly half of the original length of the animal) [Credit: Johan Lindgren]

"Ichthyosaurs are interesting because they have many traits in common with dolphins, but are not at all closely related to those sea-dwelling mammals," says research co-author Mary Schweitzer, professor of biological sciences at NC State with a joint appointment at the North Carolina Museum of Natural Sciences and visiting professor at Lund University. "We aren't exactly sure of their biology either. They have many features in common with living marine reptiles like sea turtles, but we know from the fossil record that they gave live birth, which is associated with warm-bloodedness. This study reveals some of those biological mysteries."

Johan Lindgren, associate professor at Sweden's Lund University and lead author of a paper describing the work, published in Nature, put together an international team to analyze an approximately 180 million-year-old Stenopterygius fossil from the Holzmaden quarry in Germany.

"Both the body outline and remnants of internal organs are clearly visible," says Lindgren. "Remarkably, the fossil is so well-preserved that it is possible to observe individual cellular layers within its skin."

Researchers identified cell-like microstructures that held pigment organelles within the fossil's skin, as well as traces of an internal organ thought to be the liver. They also observed material chemically consistent with vertebrate blubber, which is only found in animals capable of maintaining body temperatures independent of ambient conditions.

Lindgren sent samples from the fossil to international colleagues, including Schweitzer. The team conducted a variety of high-resolution analytical techniques, including time-of-flight secondary ion mass spectrometry (ToF SIMS), nanoscale secondary ion mass spectrometry (NanoSIMS), pyrolysis-gas chromatography/mass spectrometry, as well as immunohistological analysis and various microscopic techniques.

Schweitzer and NC State research assistant Wenxia Zheng extracted soft tissues from the samples and performed multiple, high-resolution immunohistochemical analyses. "We developed a panel of antibodies that we applied to all of the samples, and saw differential binding, meaning the antibodies for a particular protein -- like keratin or hemoglobin -- only bound to particular areas," Schweitzer says. "This demonstrates the specificity of these antibodies and is strong evidence that different proteins persist in different tissues. You wouldn't expect to find keratin in the liver, for example, but you would expect hemoglobin. And that's what we saw in the responses of these samples to different antibodies and other chemical tools."

Lindgren's lab also found chemical evidence for subcutaneous blubber. "This is the first direct, chemical evidence for warm-bloodedness in an ichthyosaur, because blubber is a feature of warm-blooded animals," Schweitzer says.

Taken together, the researchers' findings indicate that the Stenopterygius had skin similar to that of a whale, and coloration similar to many living marine animals -- dark on top and lighter on the bottom -- which would provide camouflage from predators, like pterosaurs from above, or pliosaurs from below.

"Both morphologically and chemically, we found that although Stenopterygius would be loosely considered 'reptiles,' they lost the scaly skin associated with these animals -- just as the modern leatherback sea turtle has," Schweitzer says. "Losing the scales reduces drag and increases maneuverability underwater.

"This animal's preservation is unusual, especially for a marine environment -- but then, the Holzmaden formation is known for its exceptional preservation. This specimen has given us more evidence that these tissues and molecules can preserve for extremely long periods, and that soft tissue analysis can shed light on evolutionary patterns, relationships, and how ancient animals functioned in their environment.

"Our results were repeatable and consistent across labs. This work really shows what we're capable of discovering when we perform a multidisciplinary, multi-institutional study of an exceptional specimen."

Source: North Carolina State University [December 05, 2018]

Researchers at the RIKEN Center for Biosystems Dynamics (BDR) and collaborators have described for the first time the development of the hagfish inner ear. Published in the journal Nature, the study provides a new story for inner ear evolution that began with the last common ancestor of modern vertebrates.

The eel-shaped, slime-producing hagfish is a living fossil, remaining unchanged in its structure and habits for over 300 million years [Credit: Gerald & Buff Corsi/Getty Images]

Comparing organs among related animals can be helpful when trying to understand the evolutionary process, and will ultimately help us better understand organogenesis--the process through which organs develop. This underlying philosophy helped guide the collaborative effort to study the inner ear led by Shigeru Kuratani at RIKEN BDR.

The story begins with a difference between jawed and jawless vertebrates. Jawed vertebrates like humans have inner ears with three semicircular canals, which are what allow us to sense our position and stay balanced in the world, and especially to sense 3-D acceleration. The fossil record shows that a group of jawless fish from the Paleozoic era only had two semicircular canals. In order to understand the evolutionary changes that led three canals, the team looked at the only two types of jawless vertebrates that still exist on earth: lampreys and hagfish.

Lampreys are thought to have two semicircular canals, while hagfish only have one. However, hagfish are no longer thought to be more primitive than lampreys. A series of molecular biological experiments was able to clarify the issue. Analyzing the regulatory genes that control the development of the semicircular canals showed that the basic pattern of inner ear development is similar for all vertebrates, including lampreys and hagfish. Key genes, such as Tbx1 and Patched were expressed at the same places with the same timing across all three types of vertebrate.

The anterior and posterior canals in jawed vertebrates appear to be genetically homologous to the anterior and posterior parts of the lamprey canal, while the pattern for the single hagfish canal is likely an evolved trait, not a primitive condition. The difference between the jawed and lawless fish is the presence of the common crus, a structure that connects the anterior and posterior canals in jawed vertebrates. The current study could not determine whether the common crus is something that jawed vertebrates gained or something that was lost in jawless vertebrates.

Further analysis focused on the Otx1 gene. This gene is required for proper development of the lateral canal, the third canal that is unique to jawed vertebrates. The researchers found that despite the lack of a lateral canal, lampreys and hagfish both expressed Otx1 in the proper location during development. This was somewhat surprising as its expression was thought to be an advent that led to the evolution of the lateral canal. Instead, it appears that Otx1 expression in the otic vesicle is an ancient feature for all vertebrates.

A more complete understanding will be possible by performing studies with an animal that represents the lineages before jawed and jawless vertebrates diverged.

Source: RIKEN [December 05, 2018]

A team of scientists led by Jingmai O'Connor from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Chinese Academy of Sciences, reported the first occurrence of medullary bone in Enantiornithes, the dominant clade of birds during the Cretaceous.

Main slab of Pengornithid Enantiornithine, preserved in three-dimensions unlike most compression fossils  from the Jehol Biota. Scale bar is one centimetre [Credit: Jingmai O'Connor]

Medullary bone is a bone tissue unique to birds today. It is present only in females about to lay eggs and forms in the empty spaces within the skeleton. This bone tissue serves as a reservoir for calcium needed to form the eggshell. Medullary bone has been reported in a variety of non-avian dinosaurs including Tyrannosaurus rex, ornithopod dinosaurs like Tenontosaurus, and several sauropods (huge long-necked dinosaurs) including Mussasaurus. It has also been identified in pterosaurs, which are flying reptiles closely related to dinosaurs.

Since the first report of medullary bone in a Mesozoic fossil in 2005, this tissue has attracted great interest because it links birds and dinosaurs. However, the presence of this bone tissue in pterosaurs and non-avian dinosaurs is perplexing. Non-avian dinosaurs were so large and their eggs so small that they shouldn't have required medullary bone. Since pterosaurs laid soft-shelled eggs, they also shouldn't have required medullary bone.

Cross section of the femur bone viewed under polarized light showing the thick layer of medullary bone within the medullary cavity [Credit: Jingmai O'Connor]

Some reported instances of medullary bone are probably actually bone pathologies causing abnormal growth. However, in this report, IVPP scientists, working together with Mark Norell from the American Museum of Natural History and Greg Erickson from Florida State University, argued that no previous description of medullary bone in a Mesozoic reptile was well supported.

The new report is the best support for medullary bone in the Mesozoic so far since it was found throughout the entire preserved skeleton, suggesting it was part of a system-wide process rather than a local pathology. However, the authors concede that scientists still know too little about medullary bone to confirm, without additional evidence (e.g., association with a nest or eggs), that the fossilized individual with this tissue was reproductively active.

In light of the currently available evidence, medullary bone might have been an entirely avian feature even in the Mesozoic. It evolved as a result of the thinned, hollow bones in birds, which lightened the skeleton for flight, as well as their increased egg size.

The findings were published in Nature Communications.

Source: Chinese Academy of Sciences [December 05, 2018]

Scientists are painting the clearest picture yet of what life may have been like for Neanderthals living in Southern France some 250,000 years ago, and to do it, they're using an unlikely day-to-day record of what their environment was like—their teeth.

Teeth may be an important new resource for understanding the lives of our extinct relatives, said Daniel Green, a postdoctoral fellow at the Forsyth Institute, an affiliate of Harvard Dental School of Medicine [Credit: Kris Snibbe/Harvard University]

A team of researchers showed that examining the teeth of Neanderthal infants could yield insight into nursing and weaning behavior as well as winter and summer cycles. The study even found evidence that the Neanderthals had been exposed to lead—the earliest such exposure ever recorded in any human ancestor.

The study from researchers Daniel Green, a postdoctoral fellow at the Harvard-affiliated Forsyth Institute; Tanya Smith, a former Harvard professor now at Griffith University in Australia; and Icahn School of Medicine at Mount Sinai researchers Christine Austin and Manish Arora, who is also a former postdoctoral fellow at the Harvard T.H. Chan School of Public Health, was recently published in Science Advances.

"Humans are very different from other apes," said Green, one of the first authors of the study. "We are curious to understand what made us different in evolutionary history, and a lot of people have looked to the climate to understand those differences.

"Obviously, we are changing the climate today, but in the past the climate was shaping us, and a number of theories suggest that changes in the seasonal availability of water drove us to take one part of our behavioral repertoire—stone-tool-making—and use that much more frequently," he continued.

"But that idea is hard to test … because we don't know what rainfall was like 2, 3, or 4 million years ago. It turns out teeth are a really good way of addressing this problem because they grow in rings, like a tree, but those rings are formed every day."

And much like tree rings, he said, changes in the environment—such as winters and summers—are recorded in the chemical composition of teeth, giving modern scientists a window into the seasonal patterns with which Neanderthals contended.

The study builds partly on research Green conducted several years ago as part of his Ph.D., in which he raised a flock of 10 sheep at Harvard's Concord Field Station.

"What we did was collect 700 gallons of glacial melt water from Montana, so we could give it to the sheep and contrast it with Boston water as a way to create these artificial, experimental seasons," Green said. "Everything was carefully controlled—we were measuring their body chemistry in real time, their environmental chemistry in real time, and we built a computational and statistical model to predict, based on measurements we can make in the teeth, what the seasons were like when they were living."

The technique proved to be so effective, Green said, that not only could he identify the seasonal differences between the two water supplies, he was even able to spot short-lived environmental changes like snowstorms.

"Everything was working, but we were seeing one small blip," he said. "When we went back to the animals' lives … it turned out that there had been two big snow storms that were not a planned part of the experiment. The sheep had eaten snow from the ground, and that was reflected in their tooth chemistry. So the system worked so well that it actually ended up re-creating storm events, and teaching us about our own experiment."

Informed by these findings, and adding barium and lead measurements to the oxygen isotope analyses in teeth, Smith and her international team of archaeologists, biological anthropologists, Earth scientists, and public health specialists were able to identify a similar seasonal pattern in Neanderthal teeth.

"We can see that one of the Neanderthals was born in the spring and weaned from mother's milk in the fall, and we can see they were exposed to lead a number of discrete times in the winter," Green said. "That was a striking result, and there is still a lot of mystery about it. We don't actually know where that lead comes from … but we do know that later, during the Roman period and onward, there were lead mines in the area, so it's possible that lead in the ground had contaminated some water or food sources."

What is known, Green said, is that teeth may be an important new resource for understanding the lives of our extinct relatives.

"The oxygen analysis used in this study is a new type that has been used only a few times previously," Green said. "So to validate that work, and show we can pick out these seasonal cycles from Neanderthal teeth, we looked at some of the analyses I had done for my Ph.D., used them to validate the technique, and we then applied it to Neanderthals."

Going forward, Green hopes to trace the source of lead exposure found in the Neanderthal teeth, but also believes the finding may set other scientists on the path to searching for similar exposures in other early populations. The ability to track these exposures in teeth opens the door to using the technique in contemporary populations as well, he said.

"If people are saying they have been exposed to lead or that their water isn't clean, we could go to that community and look at the teeth children are losing naturally," Green said. "We could use this type of analysis to understand who has been exposed, by how much, and what kind of interventions are needed to deal with those issues."

Green also said he hopes to see researchers apply the technique to other early human ancestors, particularly those in Africa, in an effort to understand the environmental challenges they faced as they evolved.

"I didn't expect that the very detailed and technical geochemical work I did would apply to such a salient question about the lives of Neanderthals and in Europe, so this has been very rewarding for me," he said. "It's very exciting to have these cousins who are so closely related to us, and who contributed to our DNA, and to see these very precise moments in their lives and place them in some sort of environmental and seasonal context."

Author: Peter Reuell | Source: Harvard University [December 04, 2018]

An international group of scientists led by researchers from the University of Bristol have advanced our understanding of how ancient animals saw the world by combining the study of fossils and genetics.

A fossil trilobite with its complex eye. These ancient animals were inferred to have minimally possessed four opsins, like many modern arthropods, and should have therefore been able to see colours [Credit: University of Bristol]

Ancestors of insects and crustaceans that lived more than 500 million years ago in the Cambrian period were some of the earliest active predators, but not much is known about how their eyes were adapted for hunting.

Work published in the Proceedings of the Royal Society B suggests that when fossil and genetic data are assessed in tandem, previously inaccessible and exciting conclusions about long dead species can be made.

By examining the morphological characteristics of fossils' eyes, alongside the genetic visual pigment clues, a cross-disciplinary team led by a collaboration between the University of Bristol's Davide Pisani, Professor of Phylogenomics in the School of Earth Sciences and Nicholas Roberts, Professor of Sensory Ecology in the School of Biological Sciences, were able to find that ancient predators with more complex eyes are likely to have seen in colour.

Professor Pisani remarked: "Being able to combine fossil and genetic data in this way is a really exciting frontier of modern palaeontological and biological research. Vision is key to many animals' behaviour and ecology, and understanding how extinct animals perceived their environment will help enormously to clarify how they evolved."

By calculating the time of emergence of different visual pigments, and then comparing them to the inferred age of origin of key fossil lineages, the researchers were able to work out the number of pigments likely to have been possessed by different fossil species. They found that fossil animals with more complex eyes appeared to have more visual pigments, and that the great predators of the Cambrian period may have been able to see in colour.

Dr James Fleming, Professor Pisani and Roberts' former PhD student, explained: "Animal genomes and therefore opsin genes (constituting the base of different visual pigments) evolve by processes of gene duplication. The opsin and the pigment that existed before the duplication is like a parent, and the two new opsins (and pigments) that emerge from the duplication process are like children on a family tree.

"We calculated the birth dates of these children and this allowed understanding of what the ancient world must have seemed like to the animals that occupied it. We found that while some of the fossils we considered had only one pigment and were monochromat, i.e. they saw the world as if looking into a black and white TV, forms with more complex eyes, like iconic trilobites, had many pigments and most likely saw their world in colours."

The combinations of complex eyes and multiple kinds of visual pigments are what allows animals to distinguish between different objects based on colour alone - what we know as colour vision.

Professor Roberts commented: "It is remarkable to see how in only a very few million years the view those animals' had of their world changed from greys to the colourful world we see today."

The project involved scientists from all across the world - from the UK as well as Denmark, Italy, Korea and Japan, where Dr Fleming has now moved to work as a postdoctoral researcher. Each of them brought their own specialities to this multidisciplinary work, providing expertise in genetics, vision, taxonomy and palaeontology.

Source: University of Bristol [December 04, 2018]