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Flow in the asthenosphere drags tectonic plates along

A 3D computer model of the asthenosphere by Rice University geophysicists finds that the convective cycling and pressure-driven flow can sometimes cause the asthenosphere to move even faster than the tectonic plates riding atop it.
A 3D computer model of the asthenosphere by Rice University geophysicists finds that the convective cycling and pressure-driven flow can sometimes cause the asthenosphere to move even faster than the tectonic plates riding atop it. This 2D slice of data from the model shows stronger, faster moving sections of the asthenosphere (yellow) bracketed above and below by slower, more fluid regions (orange). Credit: A. Semple/Rice University

New simulations of Earth’s asthenosphere find that convective cycling and pressure-driven flow can sometimes cause the planet’s most fluid layer of mantle to move even faster than the tectonic plates that ride atop it.

That’s one conclusion from a new study by Rice University geophysicists who modeled flow in the 100-mile-thick layer of mantle that begins at the base of Earth’s tectonic plates, or lithosphere.

The study, which is available online in the journal Earth and Planetary Science Letters, takes aim at a much-debated question in geophysics: What drives the movement of Earth’s tectonic plates, the 57 interlocking slabs of the lithosphere that slip, grind and bump against one another in a seismic dance that causes earthquakes, builds continents and gradually reshapes the planet’s surface every few million years?

“Tectonic plates float on top of the asthenosphere, and the leading theory for the past 40 years is that the lithosphere moves independently of the asthenosphere, and the asthenosphere only moves because the plates are dragging it along,” said graduate student Alana Semple, lead co-author of the new study. “Detailed observations of the asthenosphere from a Lamont research group returned a more nuanced picture and suggested, among other things, that the asthenosphere has a constant speed at its center but is changing speeds at its top and base, and that it sometimes appears to flow in a different direction than the lithosphere.”

Computational modeling carried out at Rice offers a theoretical framework that can explain these puzzling observations, said Adrian Lenardic, a study co-author and professor of Earth, environmental and planetary sciences at Rice.

“We’ve shown how these situations can occur through a combination of plate- and pressure-driven flow in the asthenosphere,” he said. “The key was realizing that a theory developed by former Rice postdoc Tobias Höink had the potential to explain the Lamont observations if a more accurate representation of the asthenosphere’s viscosity was allowed for. Alana’s numerical simulations incorporated that type of viscosity and showed that the modified model could explain the new observations. In the process, this offered a new way of thinking about the relationship between the lithosphere and asthenosphere.”

Though the asthenosphere is made of rock, it is under intense pressure that can cause its contents to flow.

“Thermal convection in Earth’s mantle generates dynamic pressure variations,” Semple said. “The weakness of the asthenosphere, relative to tectonic plates above, allows it to respond differently to the pressure variations. Our models show how this can lead to asthenosphere velocities that exceed those of plates above. The models also show how flow in the asthenosphere can be offset from that of plates, in line with the observations from the Lamont group”

The oceanic lithosphere is formed at mid-ocean ridges and flows toward subduction zones where one tectonic plate slides beneath another. In the process, the lithosphere cools and heat from Earth’s interior is transferred to its surface. Subduction recycles cooler lithospheric material into the mantle, and the cooling currents flow back into the deep interior.

Semple’s 3D model simulates both this convective cycle and the asthenosphere. She credited Rice’s Center for Research Computing (CRC) for its help running simulations — some of which took as long as six weeks — on Rice’s DAVinCI supercomputer.

Semple said the simulations show how convective cycling and pressure-driven flow can drive tectonic movement.

“Our paper suggests that pressure-driven flow in the asthenosphere can contribute to the motion of tectonic plates by dragging plates along with it,” she said. “A notable contribution does come from ‘slab-pull,’ a gravity-driven process that pulls plates toward subduction zones. Slab-pull can still be the dominant process that moves plates, but our models show that asthenosphere flow provides a more significant contribution to plate movement than previously thought.”

The research was supported by the National Science Foundation. DAVinCI is administered by CRC and was procured in partnership with Rice’s Ken Kennedy Institute for Information Technology.

Reference:
Alana G. Semple, Adrian Lenardic. Plug flow in the Earth’s asthenosphere. Earth and Planetary Science Letters, 2018; 496: 29 DOI: 10.1016/j.epsl.2018.05.030

Note: The above post is reprinted from materials provided by Rice University. Original written by Jade Boyd.

Dino-bird dandruff research head and shoulders above rest

dandruff
Dr Maria McNamara, UCC: “What’s remarkable is that the fossil dandruff is almost identical to that in modern birds.” Credit: John Sheehan

Palaeontologists from University College Cork (UCC) in Ireland have discovered 125 million-year-old dandruff preserved amongst the plumage of feathered dinosaurs and early birds, revealing the first evidence of how dinosaurs shed their skin.

UCC’s Dr Maria McNamara and her team studied the fossil cells, and dandruff from modern birds, with powerful electron microscopes for the study, published today in the journal Nature Communications.

“The fossil cells are preserved with incredible detail — right down to the level of nanoscale keratin fibrils. What’s remarkable is that the fossil dandruff is almost identical to that in modern birds — even the spiral twisting of individual fibres is still visible,” said Dr Maria McNamara.

Just like human dandruff, the fossil dandruff is made of tough cells called corneocytes, which in life are dry and full of the protein keratin.

The study suggests that this modern skin feature evolved sometime in the late Middle Jurassic, around the same time as a host of other skin features evolved. “There was a burst of evolution of feathered dinosaurs and birds at this time, and it’s exciting to see evidence that the skin of early birds and dinosaurs was evolving rapidly in response to bearing feathers,” Dr McNamara added.

Dr McNamara led the study, in collaboration with her postdoctoral researcher Dr Chris Rogers; Dr Andre Toulouse and Tara Foley, also from UCC; Dr Paddy Orr from UCD, Ireland; and an international team of palaeontologists from the UK and China.

The dandruff is the first evidence of how dinosaurs shed their skin. The feathered dinosaurs studied — Microraptor, Beipiaosaurus and Sinornithosaurus — clearly shed their skin in flakes, like the early bird Confuciusornis studied by the team and also modern birds and mammals, and not as a single piece or several large pieces, as in many modern reptiles.

Co-author Professor Mike Benton, from the University of Bristol’s School of Earth Sciences, said: “It’s unusual to be able to study the skin of a dinosaur, and the fact this is dandruff proves the dinosaur was not shedding its whole skin like a modern lizard or snake but losing skin fragments from between its feathers.”

Modern birds have very fatty corneocytes with loosely packed keratin, which allows them to cool down quickly when they are flying for extended periods. The corneocytes in the fossil dinosaurs and birds, however, were packed with keratin, suggesting that the fossils didn’t get as warm as modern birds, presumably because they couldn’t fly at all or for as long periods.

Reference:
Maria E. McNamara, Fucheng Zhang, Stuart L. Kearns, Patrick J. Orr, André Toulouse, Tara Foley, David W. E. Hone, Chris S. Rogers, Michael J. Benton, Diane Johnson, Xing Xu, Zhonghe Zhou. Fossilized skin reveals coevolution with feathers and metabolism in feathered dinosaurs and early birds. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-04443-x

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

When the dinosaurs died, so did forests — and tree-dwelling birds

The asteroid impact that eliminated non-avian dinosaurs destroyed global forests.
The asteroid impact that eliminated non-avian dinosaurs destroyed global forests. Here, a hyopothetical surviving bird lineage — small-bodied and specialized for a ground-dwelling lifestyle–flees a burning forest in the aftermath of the asteroid strike. Credit: Phillip M. Krzeminski

Sixty-six million years ago, the world burned. An asteroid crashed to Earth with a force one million times larger than the largest atomic bomb, causing the extinction of the dinosaurs. But dinosaurs weren’t the only ones that got hit hard — in a new study, scientists learned that the planet’s forests were decimated, leading to the extinction of tree-dwelling birds.

“Looking at the fossil record, at plants and birds, there are multiple lines of evidence suggesting that the forest canopies collapsed,” says Regan Dunn, a paleontologist at the Field Museum in Chicago and a co-author on the study in Current Biology. “Perching birds went extinct because there were no more perches.”

“We drew on a variety of approaches to stitch this story together,” said Daniel Field, the paper’s lead author, of the Milner Centre for Evolution at the University of Bath. “We concluded that the temporary elimination of forests in the aftermath of the asteroid impact explains why arboreal birds failed to survive across this extinction event. The ancestors of modern arboreal birds did not move into the trees until forests had recovered from the extinction-causing asteroid.”

The project’s pollen expert, Antoine Bercovici of the Smithsonian Institution and the Denver Museum of Nature and Science, helped determine that the world’s forests were destroyed by looking at microscopic fossils of pollen and spores. Dunn explains, “After a disaster like a forest fire or a volcanic eruption, the first plants to come back are the fastest colonizers — especially ferns.” That’s because ferns don’t sprout from seeds, but from spores, which are much smaller — just a single cell. “Spores are minuscule, the size of a grain of pollen, so they’re easily dispersed. They get picked up by the wind and go further than seeds can, and all they need to grow is a wet spot.”

“The spores are tiny — you could fit four across a single strand of your hair,” says Dunn. “To see them, we take a sample of rock from the time frame just after the collision and dissolve it in acid. Then we purify it so that all that remains is the organic debris, like pollen, spores and little leaf bits, then we look at them under a microscope.”

Immediately after the asteroid hit, the fossil record shows the charcoal remains of burnt trees, and then, tons of fern spores. An abundance of fern spores in the fossil record often comes on the heels of a natural disaster that destroyed larger plants like trees.

“Our study examined the fossil record from New Zealand, Japan, Europe and North America, which showed there was a mass deforestation across the globe at the end of the Cretaceous period,” says co-author Bercovici.

And with no more trees, the scientists found, tree-dwelling birds went extinct. The birds that did survive were ground-dwellers — birds whose fossilized remains show longer, sturdier legs like we see in modern ground birds like kiwis and emus. The Cretaceous equivalent of robins and sparrows, with delicate little legs made for perching on tree branches, had no place to live.

“Today, birds are the most diverse and globally widespread group of terrestrial vertebrate animals — there are nearly 11,000 living species,” says Field. “Only a handful of ancestral bird lineages succeeded in surviving the mass extinction event 66 million years ago, and all of today’s amazing living bird diversity can be traced to these ancient survivors.”

And while fossil animals like dinosaurs and birds often get more love than fossil plants, Dunn says that plants are critical to understanding life on earth. “Plants are everything, plants are the context in which all terrestrial life evolves and survives. They’re primary producers, they make energy available to all life forms by capturing it from the sun — we can’t do that.”

She also notes that while the dinosaurs and their perching bird neighbors died 66 million years ago, their plight is relevant today. “The end-Cretaceous event is the fifth mass extinction — we’re in the sixth,” says Dunn. “It’s important for us to understand what happens when you destroy an ecosystem, like with deforestation and climate change — so we can know how our actions will affect what comes after us.”

Reference:
Daniel J. Field, Antoine Bercovici, Jacob S. Berv, Regan Dunn, David E. Fastovsky, Tyler R. Lyson, Vivi Vajda, Jacques A. Gauthier. Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction. Current Biology, 2018; DOI: 10.1016/j.cub.2018.04.062

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

Study casts doubt on traditional view of pterosaur flight

Pterodactyls
This is an image of a reliable reconstruction. Soft tissues like ligaments play a big role in determining a joint’s range of motion. But soft tissues rarely fossilize, causing problems for paleontologists trying to reconstruct who extinct creatures may have lived. Now researchers have shown a new method for inferring the extent to which ligaments inhibit joint movement, which could be helpful in reconstructing ancient species. Credit: Armita Manafzadeh

Most renderings and reconstructions of pterodactyls and other extinct flying reptiles show a flight pose much like that of bats, which fly with their hind limbs splayed wide apart. But a new method for inferring how ancient animals might have moved their joints suggests that pterosaurs probably couldn’t strike that pose.

“Most of the work that’s being done right now to understand pterosaur flight relies on the assumption that their hips could get into a bat-like pose,” said Armita Manafzadeh, a Ph.D. student at Brown University who led the research with Kevin Padian of the University of California, Berkeley. “We think future studies should take into account that this pose was likely impossible, which might change our perspective when we consider the evolution of flight in pterosaurs and dinosaurs.”

The research, published in Proceedings of the Royal Society B, is an effort to help paleontologists infer the range of motion of joints in a way that takes into account the soft tissues — particularly ligaments — that play key roles in how joints work. Generally, soft tissues don’t fossilize, leaving paleontologists to infer joint motion from bones alone. And there aren’t many constraints on how that’s done, Manafzadeh says. So she wanted to find a way to use present-day animals to test the extent to which ligaments limit joint motion.

It’s an idea that started with grocery store chickens, Manafzadeh says.

“If you pick up a raw chicken at the grocery store and move its joints, you’ll reach a point where you’ll hear a pop,” she said. “That’s the ligaments snapping. But if I handed you a chicken skeleton without the ligaments, you might think that its joints could do all kinds of crazy things. So the question is, if you were to dig up a fossil chicken, how would you think its joints could move, and how wrong would you be?”

For this latest study, she used not a grocery store chicken, but dead quail. Birds are the closest living relative of extinct pterosaurs and four-winged dinosaurs. After carefully cutting away the muscles surrounding the birds’ hip joints, she manipulated the joints while taking x-ray videos. That way, she could determine the exact 3-D positions of the bones in poses where the ligaments prevented further movement.

This technique enabled Manafzadeh to map out the range of motion of the quail hip with ligaments attached, which she could then compare to the range of motion that might have been inferred from bones alone. For the bones-only poses, Manafzadeh used traditional criteria that paleontologists often use — stopping where the two bones hit each other and when the movement pulled the thigh bone out of its socket.

She found that over 95 percent of the joint positions that seemed plausible with bones alone were actually impossible when ligaments were attached.

The next step was to work out how the range of motion of present-day quail hips might compare to the range of motion for extinct pterosaurs and four-winged dinosaurs.

The assumption has long been that these creatures flew a lot like bats do. That’s partly because the wings of pterosaurs were made of skin and supported by an elongated fourth finger, which is somewhat similar to the wings of bats. Bat wings are also connected to their hind limbs, which they splay out widely during flight. Many paleontologists, Manafzadeh says, assume pterosaurs and four-winged dinosaurs did the same. But her study suggests that wasn’t possible.

In quail, a bat-like hip pose seemed possible based on bones alone, but outward motion of the thigh bone was inhibited by one particular ligament — a ligament that’s present in a wide variety of birds and other reptiles related to pterosaurs. No evidence, Manafzadeh says, suggests that extinct dinosaurs and pterosaurs wouldn’t have had this ligament, too.

And with that ligament attached, this new study suggests that the bat-like pose would be impossible. According to Manafzadeh’s work, this pose would require the ligament to stretch 63 percent more than the quail ligament can. That’s quite a stretch, she says.

“That’s a huge difference that would need to be accounted for before it can be argued that a pterosaur or ‘four-winged’ dinosaur’s hip would be able to get into this bat-like pose,” Manafzadeh said. And that, she says, may require a rethinking of the evolution of flight in these animals.

In addition to calling into question traditional ideas about flight in pterosaurs and early birds, the research also provides new ways of assessing joint mobility for any joint of any extinct species by looking at its living relatives.

“What we’ve done is to provide a reliable way to quantify in 3-D everything a joint can do,” Manafzadeh said.

She hopes other researchers will use the method to study other joint systems and to better understand how other species may have moved their joints, walked and flown.

Reference:
Armita R. Manafzadeh, Kevin Padian. ROM mapping of ligamentous constraints on avian hip mobility: implications for extinct ornithodirans. Proceedings of the Royal Society B: Biological Sciences, 2018; 285 (1879): 20180727 DOI: 10.1098/rspb.2018.0727

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

Utah fossil reveals global exodus of mammals’ near relatives to major continents

Cifelliodon wahkarmoosuch
The new species Cifelliodon wahkarmoosuch is estimated to have weighed 2.5 pounds and probably grew to be about the size of a small hare. Credit: Keck School of Medicine of USC/Jorge A. Gonzalez

A nearly 130-million-year-old fossilized skull found in Utah is an Earth-shattering discovery in one respect.

The small fossil is evidence that the super-continental split likely occurred more recently than scientists previously thought and that a group of reptile-like mammals that bridge the reptile and mammal transition experienced an unsuspected burst of evolution across several continents.

“Based on the unlikely discovery of this near-complete fossil cranium, we now recognize a new, cosmopolitan group of early mammal relatives,” said Adam Huttenlocker, lead author of the study and assistant professor of clinical integrative anatomical sciences at the Keck School of Medicine of USC.

The study, published in the journal Nature on May 16, updates the understanding of how mammals evolved and dispersed across major continents during the age of dinosaurs. It suggests that the divide of the ancient landmass Pangea continued for about 15 million years later than previously thought and that mammal migration and that of their close relatives continued during the Early Cretaceous (145 to 101 million years ago).

“For a long time, we thought early mammals from the Cretaceous (145 to 66 million years ago) were anatomically similar and not ecologically diverse,” Huttenlocker said. “This finding by our team and others reinforce that, even before the rise of modern mammals, ancient relatives of mammals were exploring specialty niches: insectivores, herbivores, carnivores, swimmers, gliders. Basically, they were occupying a variety of niches that we see them occupy today.”

The study reveals that the early mammal precursors migrated from Asia to Europe, into North America and further onto major Southern continents, said Zhe-Xi Luo, senior author of the study and a paleontologist at the University of Chicago.

Fossil find: a new species

Huttenlocker and his collaborators at the Utah Geological Survey and The University of Chicago named the new species Cifelliodon wahkarmoosuch.

Found in the Cretaceous beds in eastern Utah, the fossil is named in honor of famed paleontologist Richard Cifelli. The species name, “wahkarmoosuch” means “yellow cat” in the Ute tribe’s language in respect of the area where it was found.

Scientists used high-resolution computed tomography (CT) scanners to analyze the skull.

“The skull of Cifelliodon is an extremely rare find in a vast fossil-bearing region of the Western Interior, where the more than 150 species of mammals and reptile-like mammal precursors are represented mostly by isolated teeth and jaws,” said James Kirkland, study co-author in charge of the excavation and a Utah State paleontologist.

With an estimated body weight of up to 2.5 pounds, Cifelliodon would seem small compared to many living mammals, but it was a giant among its Cretaceous contemporaries. A full-grown Cifelliodon was probably about the size of a small hare or pika (small mammal with rounded ears, short limbs and a very small tail).

It had teeth similar to fruit-eating bats and could nip, shear and crush. It might have incorporated plants into its diet.

The newly named species had a relatively small brain and giant “olfactory bulbs” to process sense of smell. The skull had tiny eye sockets, so the animal probably did not have good eyesight or color vision. It possibly was nocturnal and depended on sense of smell to root out food, Huttenlocker said.

Supercontinent existed longer than previously thought

Huttenlocker and his colleagues placed Cifelliodon within a group called Haramiyida, an extinct branch of mammal ancestors related to true mammals. The fossil was the first of its particular subgroup — Hahnodontidae — found in North America.

The fossil discovery emphasizes that haramiyidans and some other vertebrate groups existed globally during the Jurassic-Cretaceous transition, meaning the corridors for migration via Pangean landmasses remained intact into the Early Cretaceous.

Most of the Jurassic and Cretaceous fossils of haramiyidans are from the Triassic and Jurassic of Europe, Greenland and Asia. Hahnodontidae was previously known only from the Cretaceous of Northern Africa. It is to this group that Huttenlocker argues Cifelliodon belongs, providing evidence of migration routes between the continents that are now separated in northern and southern hemispheres.

“But it’s not just this group of haramiyidans,” Huttenlocker said. “The connection we discovered mirrors others recognized as recently as this year based on similar Cretaceous dinosaur fossils found in Africa and Europe.”

Reference:
Adam K. Huttenlocker, David M. Grossnickle, James I. Kirkland, Julia A. Schultz, Zhe-Xi Luo. Late-surviving stem mammal links the lowermost Cretaceous of North America and Gondwana. Nature, 2018; DOI: 10.1038/s41586-018-0126-y

Note: The above post is reprinted from materials provided by University of Southern California. Original written by Zen Vuong.

Land rising above the sea 2.4 billion years ago changed planet Earth

A conceptual rendering suggests how Earth's land elevations and oceans may have appeared during the assembly of Kenorland, left, and later, right, after the Great Oxygenation Event. A University of Oregon-led study has potentially narrowed the window on when significant amounts of land emerged from under the ocean's surface.
A conceptual rendering suggests how Earth’s land elevations and oceans may have appeared during the assembly of Kenorland, left, and later, right, after the Great Oxygenation Event. A University of Oregon-led study has potentially narrowed the window on when significant amounts of land emerged from under the ocean’s surface. Credit: Graphic by Ilya Bindeman

Chemical signatures in shale, the Earth’s most common sedimentary rock, point to a rapid rise of land above the ocean 2.4 billion years ago that possibly triggered dramatic changes in climate and life.

In a study published in the May 24 issue of the journal Nature, researchers report that shale sampled from around the world contains archival quality evidence of almost imperceptible traces of rainwater that caused weathering of land from as old as 3.5 billion years ago.

Notable changes in the ratios of oxygen 17 and 18 with more common oxygen 16, said lead author Ilya Bindeman, a geologist at the University of Oregon, allowed researchers to read the chemical history in the rocks.

In doing so, they established when newly surfaced crust was exposed to weathering by chemical and physical processes, and, more broadly, when the modern hydrologic process of moisture distillation during transport over large continents started.

The evidence is from analyses of three oxygen isotopes, particularly the rare but stable oxygen 17, in 278 shale samples drawn from outcrops and drill holes from every continent and spanning 3.7 billion years of Earth’s history. The analyses were done in Bindeman’s Stable Isotope Laboratory.

Based on his own previous modeling and other studies, Bindeman said, total landmass on the planet 2.4 billion years ago may have reached about two-thirds of what is observed today. However, the emergence of the new land happened abruptly, in parallel with large-scale changes in mantle dynamics.

Isotopic changes recorded in the shale samples at that time also coincides with the hypothesized timing of land collisions that formed Earth’s first supercontinent, Kenorland, and high-mountain ranges and plateaus.

“Crust needs to be thick to stick out of water,” Bindeman said. “The thickness depends on its amount and also on thermal regulation and the viscosity of the mantle. When the Earth was hot and the mantle was soft, large, tall mountains could not be supported. Our data indicate that this changed exponentially 2.4 billion years ago. The cooler mantle was able to support large swaths of land above sea level.”

Temperatures on the surface when the new land emerged from the sea would have likely been hotter than today by several tens of degrees, he said.

The study found a stepwise change in triple-isotopes of oxygen around that time frame. That, the scientists said, resolves previous arguments for a gradual or stepwise emergence of land between 1.1 and 3.5 billion years ago. At 2.4 billion years ago, Bindeman said, the newly emerged land began to consume carbon dioxide from the atmosphere amid chemical weathering.

The timing also coincides with the transition from the Archean Eon, when simple prokaryotic life forms, archaea and bacteria, thrived in water, to the Proterozoic Eon, when eukaryotes, such as algae, plants and fungi, emerged.

“In this study, we looked at how weathering proceeded over 3.5 billion years,” Bindeman said. “Land rising from water changes the albedo of the planet. Initially, Earth would have been dark blue with some white clouds when viewed from space. Early continents added to reflection. Today we have dark continents because of lots of vegetation.”

Exposure of the new land to weathering, he said, may have set off a sink of greenhouse gases such carbon dioxide, disrupting the radiative balance of the Earth that generated a series of glacial episodes between 2.4 billion and 2.2 billion years ago. That, he said, may have spawned the Great Oxygenation Event in which atmospheric changes brought significant amounts of free oxygen into the air. Rocks were oxidized and became red. Archean rocks are gray.

In the absence of much land, he said, photons from the sun interacted with water and heated it. A bright surface, provided by emerging land, would reflect sunlight back into space, creating additional torque on radiative-greenhouse balance and a change in climate.

“What we speculate is that once large continents emerged, light would be reflected back into space and initiate runaway glaciation,” Bindeman said. “Earth would have seen its first snowfall.”

Shales are formed by the weathering of crust.

“They tell you a lot about the exposure to air and light and precipitation,” Bindeman said. “The process of forming shale captures organic products and eventually helps to generate oil. Shales provide us with a continuous record of weathering.”

Reference:
I. N. Bindeman, D. O. Zakharov, J. Palandri, N. D. Greber, N. Dauphas, G. J. Retallack, A. Hofmann, J. S. Lackey, A. Bekker. Rapid emergence of subaerial landmasses and onset of a modern hydrologic cycle 2.5 billion years ago. Nature, 2018; 557 (7706): 545 DOI: 10.1038/s41586-018-0131-1

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

Genome structure of dinosaurs discovered by bird-turtle comparisons

Apalone spinifera spiny softshell turtle
This is an Apalone spinifera spiny softshell turtle hatchling. Credit: Nicole Valenzuela

A discovery by scientists at the University of Kent has provided significant insight into the overall genome structure of dinosaurs.

By comparing the genomes of different species, chiefly birds and turtles, the Kent team were able to determine how the overall genome structure (i.e. the chromosomes) of many people’s favourite dinosaur species — like Velociraptor or Tyrannosaurus — might have looked through a microscope.

The research was carried out in the laboratory of Professor Darren Griffin, of the University’s School of Biosciences, and is now published in the journal Nature Communications. It involved extrapolating the likely genome structure of a shared common ancestor of birds and turtles that lived around 260 million years ago — 20 million years before the dinosaurs first emerged.

Dr Becky O’Connor, senior postdoctoral researcher and co-author of the Nature Communications paper, then traced how chromosomes changed over evolutionary time from a reptile ancestor to the present day.

The team found that, although the individual chromosomes rearranged their genes internally, this did not occur much at all between the chromosomes — what the scientists describe as ‘a significant discovery’.

Birds (which are themselves living dinosaurs) have a lot of chromosomes compared to most other species and that is possibly one of the reasons why they are so diverse. This research suggests that the pattern of chromosomes (karyotype) seen in early emerging dinosaurs and later theropods is similar to that of most birds and, again, may help explain their great diversity.

The new discovery suggests that, had scientists had the opportunity to make a chromosome preparation from a theropod dinosaur, it might have looked very similar to that of a modern-day ostrich, duck or chicken.

One of the key pieces of biotechnology that made it possible was the development of a set of fluorescent probes derived from birds that worked well on the chromosomes of turtles.

The genetics laboratory run by Professor Darren Griffin in Kent’s School of Biosciences carries out research into how genes organise into chromosomes and how that is different between species. The work is a collaboration with Dr Denis Larkin at the Royal Veterinary College in London, Iowa State University, the University of Cambridge, Oxford Genome Technologies and the Natural History Museum, London. The work is a collaboration with Dr Denis Larkin at the Royal Veterinary College in London, Iowa State University, the University of Cambridge, the Cambridge company Cytocell and the Natural History Museum, London.

Reference:
Rebecca E. O’Connor, Michael N. Romanov, Lucas G. Kiazim, Paul M. Barrett, Marta Farré, Joana Damas, Malcolm Ferguson-Smith, Nicole Valenzuela, Denis M. Larkin, Darren K. Griffin. Reconstruction of the diapsid ancestral genome permits chromosome evolution tracing in avian and non-avian dinosaurs. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-04267-9

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

Major fossil study sheds new light on emergence of early animal life 540 million years ago

Cambrian predator and stem-lineage euarthropod Anomalocaris canadensis from the Burgess Shale, Canada.
These are exceptionally preserved soft-bodied fossils of the Cambrian predator and stem-lineage euarthropod Anomalocaris canadensis from the Burgess Shale, Canada. Top left: Frontal appendage showing segmentation similar to modern-day euarthropods. Bottom right: Full body specimen showing one pair of frontal appendages (white arrows) and mouthparts consisting of plates with teeth (black arrow) on the head. Credit: A. Daley

All the major groups of animals appear in the fossil record for the first time around 540-500 million years ago — an event known as the Cambrian Explosion — but new research from the University of Oxford in collaboration with the University of Lausanne suggests that for most animals this ‘explosion’ was in fact a more gradual process.

The Cambrian Explosion produced the largest and most diverse grouping of animals the Earth has ever seen: the euarthropods. Euarthropoda contains the insects, crustaceans, spiders, trilobites, and a huge diversity of other animal forms alive and extinct. They comprise over 80 percent of all animal species on the planet and are key components of all of Earth’s ecosystems, making them the most important group since the dawn of animals over 500 million years ago.

A team based at Oxford University Museum of Natural History and the University of Lausanne carried out the most comprehensive analysis ever made of early fossil euarthropods from every different possible type of fossil preservation. In an article published today in the Proceedings of the National Academy of Sciences they show that, taken together, the total fossil record shows a gradual radiation of euarthropods during the early Cambrian, 540-500 million years ago.

The new analysis presents a challenge to the two major competing hypotheses about early animal evolution. The first of these suggests a slow, gradual evolution of euarthropods starting 650-600 million years ago, which had been consistent with earlier molecular dating estimates of their origin. The other hypothesis claims the nearly instantaneous appearance of euarthropods 540 million years ago because of highly elevated rates of evolution.

The new research suggests a middle-ground between these two hypotheses, with the origin of euarthropods no earlier than 550 million years ago, corresponding with more recent molecular dating estimates, and with the subsequent diversification taking place over the next 40 million years.

“Each of the major types of fossil evidence has its limitation and they are incomplete in different ways, but when taken together they are mutually illuminating and allow a coherent picture to emerge of the origin and radiation of the euarthropods during the lower to middle Cambrian,” explains Professor Allison Daley, who carried out the work at Oxford University Museum of Natural History and at the University of Lausanne. “This indicates that the Cambrian Explosion, rather than being a sudden event, unfolded gradually over the ~40 million years of the lower to middle Cambrian.”

The timing of the origin of Euarthropoda is very important as it affects how we view and interpret the evolution of the group. By working out which groups developed first we can trace the evolution of physical characteristics, such as limbs.

It has been argued that the absence of euarthropods from the Precambrian Period, earlier than around 540 million years ago, is the result of a lack of fossil preservation. But the new comprehensive fossil study suggests that this isn’t the case.

“The idea that arthropods are missing from the Precambrian fossil record because of biases in how fossils are preserved can now be rejected,” says Dr Greg Edgecombe FRS from the Natural History Museum, London, who was not involved in the study. “The authors make a very compelling case that the late Precambrian and Cambrian are in fact very similar in terms of how fossils preserve. There is really just one plausible explanation — arthropods hadn’t yet evolved.”

Harriet Drage, a PhD student at Oxford University Department of Zoology and one of the paper’s co-authors, says: “When it comes to understanding the early history of life the best source of evidence that we have is the fossil record, which is compelling and very complete around the early to middle Cambrian. It speaks volumes about the origin of euarthropods during an interval of time when fossil preservation was the best it has ever been.”

Reference:
Allison C. Daley, Jonathan B. Antcliffe, Harriet B. Drage, Stephen Pates. Early fossil record of Euarthropoda and the Cambrian Explosion. Proceedings of the National Academy of Sciences, 2018; 201719962 DOI: 10.1073/pnas.1719962115

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

Japanese student discovers new crustacean species in deep sea hydrothermal vent

Stygiopontius senokuchiae
Image of a male Stygiopontius senokuchiae taken with a confocal laser microscope. This new species of copepod was discovered by Kumamoto University student, Reina Senokuchi. The white scale bar is 0.2 mm long. Credit: Photograph by Kumamoto University Associate Professor Takeshi Kitano

A new species of microcrustacean (Stygiopontius ) was collected from a submarine hot spring (hydrothermal vent) of a volcanic seamount (Myojin-sho caldera) in the Pacific Ocean off the coast of Japan. This crustacean group lives only around deep-sea hydrothermal vents in the central Atlantic or eastern Pacific Oceans. The new species is the first of its kind discovered in Japanese waters. Reina Senokuchi, a Kumamoto University student, was the first to make the discovery saying, “When I realized that it might be a new species, I was both delighted and very surprised. I couldn’t believe it was true.”

Portals to New Worlds

There are many hydrothermal vents in the deep waters east of Japan. The water in these vents is heated by volcanic activity under the ocean floor blown into the sea. In the vicinity of these openings, bacteria function as the primary producer of organic matter and convert mineral resources contained in the hot water into energy, a process called chemosynthesis. The organisms here are not found in any other type of environment on the planet. Some can be found in vents throughout the world’s oceans, yet others appear to live only in specific areas.

A research group headed by Associate Professor Motohiro Shimanaga of Kumamoto University studies the ecosystems of deep sea hydrothermal vents. Between 2012 and 2014, Dr. Shimanaga’s group surveyed hydrothermal vents in the calderas of three submarine volcanos in the Izu Islands (in the Izu-Bonin Arc) and collected samples of organisms to learn more about these mysterious life forms.

Research on the Pacific Rim

The area surveyed included hydrothermal vents at depths between 800 and 1400 meters in the Myojin-sho caldera, the Myojin abyssal hill, and the Bayonnaise abyssal hill, which are about 420 km south of Tokyo. Researchers mapped the areas and retrieved samples using an unmanned deep-sea sub. One of the samples included the new species of Stygiopontius, a type of copepod.

Copepods can be found all over the earth. They are ecologically important because they feed on phytoplankton and are a food source for many other creatures. Until this discovery, copepods of the genus Stygiopontius had only been found in deep sea hydrothermal vents in the center of the Atlantic and East Pacific Oceans, but not in the deep waters east of Japan.

When Ms. Reina Senokuchi, a student of Kumamoto University at that time of the study, examined the copepod from the Japan coast sample, she discovered that it had several morphological differences compared to other species of the genus Stygiopontius. Both male and female specimens of the new Stygiopontius species were found at all three investigation sites, with body lengths of 685 to 786 micrometers for females and 446 to 483 micrometers for males. Assistant Professor Daisuke Uyeno of Kagoshima University, an expert in morphological analysis of microorganisms, conducted an analysis of this tiny copepod and published a paper on the group’s findings.

The new species was named Stygiopontius senokuchiae after its discoverer Ms. R. Senokuchi. “I was very happy because I did not think it would be named before I graduated. It was definitely worth the effort to sketch out the microscopic observations,” she said upon hearing the news.

“Our next challenge is to figure out how this species adapted to the deep sea hydrothermal vent environment,” said Ms. Senokuchi’s mentor, Dr. Shimanaga. “We are also very interested in clarifying just how this species has spread from one hydrothermal zone to another, since the distances between the vents are relatively large.”

Reference:
DAISUKE UYENO, HIROMI K WATANABE, MOTOHIRO SHIMANAGA. A new dirivultid copepod (Siphonostomatoida) from hydrothermal vent fields of the Izu-Bonin Arc in the North Pacific Ocean. Zootaxa, 2018; 4415 (2): 381 DOI: 10.11646/zootaxa.4415.2.8

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

Establishing a time scale for 10 million years ago

The exposure of the Neogene strata in the Linxia Basin of Gansu Province. Credit: Science China Press

The timescale is the basis to reconstruct the history of the Earth and biological evolution. A research on a chronostratigraphic sequence of the Chinese Neogene with accurate geological datings was published online in Science China: Earth Sciences.

The Chinese Neogene terrestrial deposits are widely exposed. In the Linxia Basin of Gansu Province, for example, there are continuous deposits from the Oligocene to Pleistocene, covering the complete Neogene period and bearing rich mammalian fossils (Fig. 1). The rapidly evolved mammalian fossils contribute efficiently to the division and correlation of Neogene strata. A uniform Neogene biostratigraphic framework for China has already been established, with seven mammalian ages named. With a developed stratigraphic basis for the geochronologic ages, seven chronostratigraphic stages have been established for the Chinese Neogene terrestrial strata, namely the Miocene Xiejian (Fig. 2), Shanwangian, Tunggurian, Bahean, and Baodean stages, and the Pliocene Gaozhuangian and Mazegouan stages.

Based on a series of research achievements, refined biostratigraphic, paleomagnetic and isotopic methods were combined and applied to continuous sections, and a Chinese Neogene chronostratigraphic sequence with accurate geological ages was established and improved by the research team of Prof. Deng Tao at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences in recent years. The researchers published their study, titled “Neogene integrative stratigraphy and timescale of China,” in Science China: Earth Sciences.

In Eurasia, Chinese Neogene deposits are more suitable for the establishment of an accurate Neogene biostratigraphic sequence than those of Europe, since the terrestrial deposits in Europe often limited, and many important faunas are unearthed from fissure-fillings. Chinese Neogene deposits are widespread and well suited for magnetostratigraphic analysis, despite the few radiometric dates available. The lower boundaries of most of the stages could be correlated with those of the marine stages in the International Chronostratigraphic Chart, except the Tunggurian Stage, which is correlated with the European land mammal age.

The biostratigraphic markers of the Chinese Neogene stages are usually first appearance of a single taxon, some representing regional species replacement, others indicating intercontinental migration of certain taxa. For instance, the lower boundaries of the two Upper Miocene stages, Bahean and Baodean have the first appearances of Hipparion dongxiangense and H. forstenae (Fig. 3) as biostratigraphic markers, respectively, and the geological ages of their lower boundaries are corresponding to those of the marine Tortonian (11.63 Ma) and Messinian (7.25 Ma).

The Chinese Neogene mammalian biostratigraphic divisions have become the core to establish the Asian framework. Candidate stratotype sections have been proposed for all the Chinese Neogene stages according to the principle and rule of modern stratigraphy, and other Chinese Neogene strata in different regions are comprehensively correlated.

Reference:
Tao Deng et al, Neogene integrative stratigraphy and timescale of China, Science China Earth Sciences (2018). DOI: 10.1007/s11430-017-9155-4

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

How does a one-tonne dino hatch its eggs?

Feathered carnivores called oviraptorosaurs did not sit directly on their eggs, so as not to crush them, a new study found

Most dinosaurs buried their eggs and hoped for the best, but some species—including a few hefty ones—built nests and pampered unhatched offspring much as birds do today, researchers reported Wednesday.

Which raises an intriguing question: How did creatures nearly as heavy as a hippo brood eggs without squashing them?

“Large species may have not sat directly on their eggs,” explained Kohei Tanaka, a researcher at Nagoya University Museum and lead author of a study in Biology Letters that details the incubation strategy of feathered carnivores called oviraptorosaurs.

“Eggs are arranged in a circular pattern with a large central opening,” he told AFP, describing clutches of potato-shaped eggs found in China up to half-a-metre (20 inches) long and weighing up to seven kilos (15 pounds) each.

“The dinosaurs likely sat in the middle of the nest so that they didn’t crush the eggs.”

That didn’t keep the unborn dinos warm, but it may have protected them from predators and the elements, Tanaka speculated.

Modern birds descend from a large group of mostly carnivorous dinosaurs called theropods, all of which—including the fearsome T-rex—are thought to have laid eggs.

But very few theropods built nests, which is why the brooding displayed by oviraptorosaurs—a clade of several dozen species ranging from the turkey-sized Caudipteryx to the 1.4-tonne Gigantoraptor—is so important.

Sitting on eggshells

“The incubation behaviour of birds—such as adults sitting in the nest and possibly brooding—likely evolved from theropod dinosaurs,” said Tanaka. “Our research provides additional evidence.”

Oviraptorosaurs lived during the Cretaceous period, the 80 million years leading up to the asteroid or comet strike blamed for wiping out non-avian, terrestrial dinosaurs.

They had short snouts and beak-like jaws with few or no teeth, and some sported bony crests on their heads. Evidence of generous plumage—especially on the tail—has been found on several species.

Besides the spoke-like arrangement of the fossilised eggs, the eggshell itself provided further evidence that large oviraptorosaurs sat near their unborn progeny, not on top of them.

The eggs of big dinos, the researchers discovered, were more fragile than the eggs of smaller ones, which were clearly designed to carry more weight.

How big is too big to park a dino butt on top of unhatched eggs?

“That’s hard to say,” said Tanaka. “There is a gap in the data, but the threshold should be between 200 and 500 kilos (440 and 1,110 pounds).”

Oviraptorosaurs were falsely accused by early paleontologists of stealing the eggs so often found along side their fossil remains, giving rise to their name: “egg-thief lizards.”

Reference:
Incubation behaviours of oviraptorosaur dinosaurs in relation to body size, Biology Letters, DOI: 10.1098/rsbl.2018.0135 

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

Major shift in marine life occurred 33 million years later

sea-lilies
A news study shows how sea-lilies were in the Southern Hemisphere until much more recently than previously thought. Credit: Pete Bucktrout @ BAS

A new study of marine fossils from Antarctica, Australia, New Zealand and South America reveals that one of the greatest changes to the evolution of life in our oceans occurred more recently in the Southern Hemisphere than previously thought. The results are published today (17 May 2018) in the journal Communications Biology.

The Marine Mesozoic Revolution (MMR) is a key theory in evolutionary history. While dinosaurs ruled the land, profound changes occurred in the shallow seas that covered the Earth.

During the Mesozoic, around 200 million years ago, marine predators evolved that could drill holes and crush the shells of their prey. And although small in comparison to dinosaurs, these new predators, including crustacea and some types of modern fish, had a dramatic impact on marine life.

Among the species most heavily affected were sea lilies or isocrinids — invertebrates tethered to the seafloor by graceful stalks. Side on, these stalks resemble a vertebral column; in cross section, they are shaped like a five-pointed star — because sea lilies are related to starfish, sea urchins, and sand dollars. At their height during the Paleozoic, forests of sea lilies carpeted seafloors the world over.

Their restricted ability to move made sea lilies vulnerable to the new predators, so during the MMR they were forced into deeper waters in order to survive. Because it marked such a radical change in marine communities, scientists have long sought to understand this shift. They believed it occurred around 66 million years ago, but this new study shows that in the Southern Hemisphere, sea lilies remained in shallow waters until much more recently — around 33 million years ago.

A team from British Antarctic Survey, the University of Cambridge, the University of Western Australia, and the Royal Botanic Gardens, Victoria, made the discovery when they brought together field samples from Antarctica and Australia, with fossils from museum collections for the first time. The study provides conclusive evidence that this change happened at different times in different parts of the globe, and in the Antarctic and Australia, sea lilies hung on in shallow waters until the end of the Eocene, around 33 million years ago and it is unknown exactly why.

The study shows that knowing more about the Antarctic can reshape — or overturn — existing scientific theories.

According to lead author Dr Rowan Whittle from British Antarctic Survey: “It is surprising to see such a difference in what was happening at either end of the world. In the Northern Hemisphere these changes happened whilst the dinosaurs ruled the land, but by the time these sea lilies moved into the deep ocean in the Southern Hemisphere the dinosaurs had been extinct for over 30 million years.

“Given how the ocean is changing and projected to change in the future it is vital that we understand how different parts of the world could be affected in different ways and at a range of timescales.”

To get this richer picture of how sea lilies responded to the changing oceans of the Southern Hemisphere over millions of years, the team travelled to some of the remotest regions of Western Australia and Antarctica. Their hunt for fossil sea lilies was rewarded by the discovery of nine new species.

Co-author Dr Aaron Hunter from the University of Cambridge says: “We have documented how these sea lilies evolved as Australia split away from Antarctica moving north and becoming the arid outback we know today, while ice formed over the South Polar Region.

“The sea lilies survived in the shallow waters for millions of years longer than their Northern Hemisphere cousins, but as the continents moved further apart, they eventually had nowhere to go but the deep ocean depths where they have clung on to existence to this day.”

Reference:
Rowan J. Whittle, Aaron W. Hunter, David J. Cantrill, Kenneth J. McNamara. Globally discordant Isocrinida (Crinoidea) migration confirms asynchronous Marine Mesozoic Revolution. Communications Biology, 2018; 1 (1) DOI: 10.1038/s42003-018-0048-0

Note: The above post is reprinted from materials provided by British Antarctic Survey.

Yellowstone ‘extremely relevant’ to origin of life

Yellowstone National Park
Yellowstone National Park

Montana State University scientists have found a new lineage of microbes living in Yellowstone National Park’s thermal features that sheds light on the origin of life, the evolution of archaeal life and the importance of iron in early life.

Professor William Inskeep and his team of researchers published their findings May 14 in the scientific journal Nature Microbiology.

“The discovery of archaeal lineages is critical to our understanding of the universal tree of life and evolutionary history of the Earth,” the group wrote. “Geochemically diverse thermal environments in Yellowstone National Park provide unprecedented opportunities for studying archaea in habitats that may represent analogues of early Earth.”

Archaea is one of the three domains of life, the others being bacteria and eukaryotes. Like bacteria, archaea are single-cell organisms. The eukaryote domain contains more cellularly complex organisms, such as humans, other animals, plants and fungi.

The scientists called the new archaeal lineage Marsarchaeota after Mars, the red planet, because these organisms thrive in habitats containing iron oxides. Within Marsarchaeota, they discovered two main subgroups that live throughout Yellowstone and thrive in hot, acidic water where iron oxide is the main mineral. One subgroup lives in water above 122 degrees Fahrenheit, and the other lives in water above 140 to 176 degrees. The water is about as acidic as grapefruit juice. Their microbial mats are red because of the iron oxide.

“It’s interesting that the habitat of these organisms contains (iron) minerals similar to those found on the surface of Mars,” Inskeep said.

He added that microbes produce iron oxide, but the Marsarchaeota do not. They might be involved in reducing iron into a simpler form, “which is important from an early Earth standpoint. Iron cycling has been implicated as being extremely important in early Earth conditions.”

The Marsarchaeota live fairly deep in microbial mats, but they still require low levels of oxygen, Inskeep said. The subgroups are so abundant that, together, they can account for as much as half of the organisms living within a single microbial mat.

The scientists studied microbial mats throughout Yellowstone. Microorganisms in these “microbial beaver dams” produce iron oxide that creates terraces, which, in turn, block streams. As water (only a couple of millimeters deep) runs over the terraces, oxygen is captured from the atmosphere and supplied to the Marsarchaeota.

“Physics comes together with chemistry and microbiology,” Inskeep said. “It’s like a sweet spot of conditions that this group of organisms likes.”

In addition to learning more about life on early Earth and the potential for life on Mars, Inskeep said the research can help scientists understand more about high-temperature biology.

“Knowing about this new group of archaea provides additional pieces of the puzzle for understanding high-temperature biology,” he said. “That could be important in industry and molecular biology.”

The work that resulted in the Nature Microbiology paper was the culmination of research that took place over the past decade, said Inskeep, who has studied the geochemistry and microbiology of Yellowstone’s high-temperature environments for the last 20 years. Inskeep is a professor of geomicrobiology in MSU’s Department of Land Resources and Environmental Sciences in the College of Agriculture and co-founder of MSU’s Thermal Biology Institute.

The lead authors of the Nature Microbiology paper earned their doctorates at MSU and were part of NSF’s Integrative Graduate Education and Research Traineeship (IGERT) program while at MSU. Zackary Jay is now a postdoctoral researcher in the Department of Chemical and Biological Engineering in the Norm Asbjornson College of Engineering and the Center for Biofilm Engineering at MSU. Jacob Beam is now a postdoctoral researcher at Bigelow Laboratory for Ocean Sciences at East Boothbay, Maine.

“In the end, after many years of work, it’s exciting, and a relief, to have our team’s work recognized and published, particularly in a high impact journal,” Jay said.

Other co-authors were Mensur Dlakic from MSU’s Department of Microbiology and Immunology in the College of Letters and Science and College of Agriculture; Douglas Rusch from the Center for Bioinformatics at Indiana University; and Mark Kozubal from the Thermal Biology Institute, MSU’s Department of Land Resources and Environmental Sciences, and Sustainable Bioproducts in Bozeman.

The Yellowstone research was a collaboration involving the Thermal Biology Institute, the Montana Agriculture Experiment Station (MAES) and the Yellowstone Center for Resources (National Park Service). Funding came from IGERT, the Pacific Northwest National Laboratory and MAES. The U.S. Department of Energy Joint Genome Institute in Walnut Creek, California, sponsored the genetic sequencing.

Reference:
Zackary J. Jay, Jacob P. Beam, Mensur Dlakić, Douglas B. Rusch, Mark A. Kozubal, William P. Inskeep. Marsarchaeota are an aerobic archaeal lineage abundant in geothermal iron oxide microbial mats. Nature Microbiology, 2018; DOI: 10.1038/s41564-018-0163-1

Note: The above post is reprinted from materials provided by Montana State University. Original written by Evelyn Boswell.

Fossil record reveals changes in Earth’s movement and rotation

Earth

Professor James Crampton from Victoria University’s School of Geography, Environment, and Earth Sciences worked with a research team from GNS Science and the Universities of Wisconsin, California Riverside, and Chicago to examine the fossils of graptoloids, an extinct type of plankton that floated in ancient oceans. They found evidence that regular changes in the Earth’s orbit and axis of rotation caused significant changes in both the evolution and extinction rates of these creatures.

“This research is very exciting, because the relationship between these orbital changes and extinction has never been shown before in truly ancient ecosystems,” says Professor Crampton. “There’s a strong debate in science about the impact on extinction and evolution of environmental change versus interactions between species (such as competition for food). With this study we can provide evidence of the impact of environmental changes on life on Earth. The evolution cycle changes we see occurred relatively soon after the first evolution of complex ecosystems, and during one of the greatest bursts of biodiversity increase in the history of life.”

Normally, changes in Earth’s orbit would be calculated by astronomers, Professor Crampton says, rather than palaeontologists.

“Astronomers can clearly calculate changes in Earth’s orbit about 50 million years into the past, but beyond that point the calculations become impossible due to the effects of what we call chaos theory, which makes the calculations too complex to complete,” Professor Crampton says. “But we can see the effects of changes in Earth’s orbit in the fossil record, so we can provide information to astronomers that they previously couldn’t find out.”

Understanding the evolution of plankton is also extremely important to understanding life on Earth today, Professor Crampton says.

“Plankton living in the oceans today absorb a large amount of our CO2 output, keeping it out of the atmosphere,” Professor Crampton says. “They are also an important part of the food chain. The evolution and extinction of plankton can have a large effect on marine life.”

This research is only the beginning. Professor Crampton and his colleagues now plan to look deeper into the specific causes of extinction.

“We know that changes in Earth’s orbit affects extinction and evolution,” Professor Crampton says. “What we’re missing is the information in the middle – what was happening on Earth as a result of orbital changes that caused extinction or evolution. Other research teams around the world are trying to extract sufficiently detailed information about climate change between 400 and 500 million years ago so that we can figure out exactly what the relationship is between climate changes and the plankton.

“We also want to look more closely at what happens after a species becomes extinct,” Professor Crampton says. “We know that when a species becomes extinct a new species will evolve to take the place of the extinct species in an ecosystem, but we don’t know how long that takes.

“We’re lucky to have such a good fossil record of this group, built up over many years by GNS and the University of California Riverside, because it answers so many questions for us,” says Professor Crampton. “With this fossil record we can ask fundamental questions about biodiversity and how life works on Earth.”

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

Jurassic fossil tail tells of missing link in crocodile family tree

Magyarosuchus fitosi
Artist’s impression of Magyarosuchus fitosi. Credit: Marton Szabo

A 180-million-year-old fossil has shed light on how some ancient crocodiles evolved into dolphin-like animals.

The specimen — featuring a large portion of backbone — represents a missing link in the family tree of crocodiles, and was one of the largest coastal predators of the Jurassic Period, researchers say.

The newly discovered species was nearly five metres long and had large, pointed teeth for grasping prey. It also shared key body features seen in two distinct families of prehistoric crocodiles, the team says.

Some Jurassic-era crocodiles had bony armour on their backs and bellies, and limbs adapted for walking on land. Another group had tail fins and flippers but did not have armour.

The new species was heavily armoured but also had a tail fin, suggesting it is a missing link between the two groups, researchers say.

It has been named Magyarosuchus fitosi in honour of the amateur collector who discovered it, Attila Fitos.

The fossil — unearthed on a mountain range in north-west Hungary in 1996 and stored in a museum in Budapest — was examined by a team of palaeontologists, including a researcher from the University of Edinburgh.

It was identified as a new species based on the discovery of an odd-looking vertebra that formed part of its tail fin.

The study, published in the journal PeerJ, also involved researchers in Hungary and Germany. It was supported by the Leverhulme Trust and the SYNTHESYS project, part of the European Commission’s Seventh Framework Programme.

Dr Mark Young, of the University of Edinburgh’s School of GeoSciences, who was involved in the study, said: “This fossil provides a unique insight into how crocodiles began evolving into dolphin and killer whale-like forms more than 180 million years ago. The presence of both bony armour and a tail fin highlights the remarkable diversity of Jurassic-era crocodiles.”

Reference:
Attila Ősi, Mark T. Young, András Galácz, Márton Rabi. A new large-bodied thalattosuchian crocodyliform from the Lower Jurassic (Toarcian) of Hungary, with further evidence of the mosaic acquisition of marine adaptations in Metriorhynchoidea. PeerJ, 2018; 6: e4668 DOI: 10.7717/peerj.4668

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

25 years of fossil collecting yields clearest picture of extinct 12-foot aquatic predator

Hyneria lindae
A rendition of what the Hyneria lindae might have looked like. Credit: Jason Poole of the Academy of Natural Sciences of Drexel University.

After 25 years of collecting fossils at a Pennsylvania site, scientists at the Academy of Natural Sciences of Drexel University now have a much better picture of an ancient, extinct 12-foot fish and the world in which it lived.

Although Hyneria lindae was initially described in 1968, it was done without a lot of fossil material to go on. But since the mid-1990s, dedicated volunteers, students, and paleontologists digging at the Red Hill site in northern Pennsylvania’s Clinton County have turned up more — and better quality — fossils of the fish’s skeleton that have led to new insights.

Academy researchers Ted Daeschler, PhD, and Jason Downs, PhD, who specialize in the Devonian time period (a time before dinosaurs and even land animals) when Hyneria lived, have been able to reconstruct that the predator had a blunt, wide snout, reached 10-12 feet in length, had small eyes and featured a sensory system that allowed it to hunt prey by feeling pressure waves around it.

“Dr. Keith Thomson, the man who first described Hyneria in 1968, did not have enough fossil material to reconstruct the anatomy that we have now been able to document with more extensive collections,” explained Daeschler, curator of Vertebrate Zoology at the Academy, as well as a professor in Drexel’s College of Arts and Sciences.

Originally, pieces of the fish were collected in the 1950s. Thomson described and officially named Hyneria lindae in 1968, but he had just a few pieces of a crushed skull and some scales to work with.

The new discoveries that Daeschler and Downs (who is an assistant professor at Delaware Valley University) wrote about in the Journal of Vertebrate Paleontology were made possible by years of collecting that turned up, “well-preserved, well-prepared three-dimensional material of almost all of the [bony] parts of the skeleton,” according to Downs.

No single complete skeleton exists of this giant, but enough is there to show that Hyneria would have truly been a monster to the other animals in the subtropical streams of the Devonian Period, roughly 365 million years ago. An apex predator, Hyneria’s mouth was bristling with two-inch fangs. For reference, that’s bigger than most modern Great White Shark’s teeth.

Due to its sheer size, weaponry, and sensory abilities, Hyneria may have preyed upon anything from ancient placoderms (armored fish), to acanthodians (related to sharks) and sarcopterygians (lobe-finned fish, the group Hyneria belongs to) — including early tetrapods (limbed vertebrates) that are also found at the site.

Since the streams Hyneria lived in were likely murky and not conducive to hunting by eyesight, sensory canals allowed it to detect fish swimming near it and attack them.

“We discovered that the skull roof elements have openings on their surfaces that connect up, forming a network of tubes that would function like the sensory line system in some modern aquatic vertebrates,” Daeschler said. “Similarly, we found a network of connected pores on the parts of the scales that would be exposed on the body of Hyneria.”

All of the new information gleaned about Hyneria is doubly valuable because it provides more information about the ecosystem — and time period — it lived in. The Devonian was a pivotal time in vertebrate evolution, especially since some of Hyneria’s fellow lobe-finned fish developed specialized fins that would take them onto land and eventually give rise to all limbed verterbates including reptiles, amphibians and mammals.

“Hyneria lived in a time and place that is of incredible interest to those of us studying the vertebrate fin-to-limb transition,” Downs commented. “Each study like this one contributes more to our understanding of these ecosystems and what may have played a part in the successful transition to land.”

Reference:
Edward B. Daeschler, Jason P. Downs. New description and diagnosis of Hyneria lindae (Sarcopterygii, Tristichopteridae) from the Upper Devonian Catskill Formation in Pennsylvania, U.S.A.. Journal of Vertebrate Paleontology, 2018; e1448834 DOI: 10.1080/02724634.2018.1448834

Note: The above post is reprinted from materials provided by Drexel University. Original written by Frank Otto.

Scientists find the first bird beak, right under their noses

Ichthyornis dispar
Fossil reconstruction and illustration of Ichthyornis dispar. Credit: Michael Hanson/Yale University

Researchers have pieced together the three-dimensional skull of an iconic, toothed bird that represents a pivotal moment in the transition from dinosaurs to modern-day birds.

Ichthyornis dispar holds a key position in the evolutionary trail that leads from dinosaurian species to today’s avians. It lived nearly 100 million years ago in North America, looked something like a toothy seabird, and drew the attention of such famous naturalists as Yale’s O.C. Marsh (who first named and described it) and Charles Darwin.

Yet despite the existence of partial specimens of Ichthyornis dispar, there has been no significant new skull material beyond the fragmentary remains first found in the 1870s. Now, a Yale-led team reports on new specimens with three-dimensional cranial remains — including one example of a complete skull and two previously overlooked cranial elements that were part of the original specimen at Yale — that reveal new details about one of the most striking transformations in evolutionary history.

“Right under our noses this whole time was an amazing, transitional bird,” said Yale paleontologist Bhart-Anjan Bhullar, principal investigator of a study published in the journal Nature. “It has a modern-looking brain along with a remarkably dinosaurian jaw muscle configuration.”

Perhaps most interesting of all, Bhullar said, is that Ichthyornis dispar shows us what the bird beak looked like as it first appeared in nature.

“The first beak was a horn-covered pincer tip at the end of the jaw,” said Bhullar, who is an assistant professor and assistant curator in geology and geophysics. “The remainder of the jaw was filled with teeth. At its origin, the beak was a precision grasping mechanism that served as a surrogate hand as the hands transformed into wings.”

The research team conducted its analysis using CT-scan technology, combined with specimens from the Yale Peabody Museum of Natural History; the Sternberg Museum of Natural History in Fort Hays, Kan.; the Alabama Museum of Natural History; the University of Kansas Biodiversity Institute; and the Black Hills Institute of Geological Research.

Co-lead authors of the new study are Daniel Field of the Milner Centre for Evolution at the University of Bath and Michael Hanson of Yale. Co-authors are David Burnham of the University of Kansas, Laura Wilson and Kristopher Super of Fort Hays State University, Dana Ehret of the Alabama Museum of Natural History, and Jun Ebersole of the McWane Science Center.

“The fossil record provides our only direct evidence of the evolutionary transformations that have given rise to modern forms,” said Field. “This extraordinary new specimen reveals the surprisingly late retention of dinosaur-like features in the skull of Ichthyornis — one of the closest-known relatives of modern birds from the Age of Reptiles.”

The researchers said their findings offer new insight into how modern birds’ skulls eventually formed. Along with its transitional beak, Ichthyornis dispar had a brain similar to modern birds but a temporal region of the skull that was strikingly like that of a dinosaur — indicating that during the evolution of birds, the brain transformed first while the remainder of the skull remained more primitive and dinosaur-like.

“Ichthyornis would have looked very similar to today’s seabirds, probably very much like a gull or tern,” said Hanson. “The teeth probably would not have been visible unless the mouth was open but covered with some sort of lip-like, extra-oral tissue.”

In recent years Bhullar’s lab has produced a large body of research on various aspects of vertebrate skulls, often zeroing in on the origins of the avian beak. “Each new discovery has reinforced our previous conclusions. The skull of Ichthyornis even substantiates our molecular finding that the beak and palate are patterned by the same genes,” Bhullar said. “The story of the evolution of birds, the most species-rich group of vertebrates on land, is one of the most important in all of history. It is, after all, still the age of dinosaurs.”

Reference:
Daniel J. Field, Michael Hanson, David Burnham, Laura E. Wilson, Kristopher Super, Dana Ehret, Jun A. Ebersole, Bhart-Anjan S. Bhullar. Complete Ichthyornis skull illuminates mosaic assembly of the avian head. Nature, 2018; 557 (7703): 96 DOI: 10.1038/s41586-018-0053-y

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

Volcanic hazard scenarios: Mount Taranaki, New Zealand

Volcanic hazard scenarios for Plinian eruptions at Mount Taranaki's summit crater and Fanthams Peak vent.
Volcanic hazard scenarios for Plinian eruptions at Mount Taranaki’s summit crater and Fanthams Peak vent. A-F: Scenario I. Close-conduits and conduit decompression by vent unroofing and dome collapse. G-K: Scenario II. Transient open and clogged conduits by repeated plugging-and-bursting of gas-depleted or chilled magma. L-O: Scenario III. Rapid progression into steady phases by open conduits. P: Possible upper conduit dynamics for each scenario based on data and interpretations of Torres-Orozco et al. (2017a, 2017b). Credit: R. Torres-Orozco et al., GSA Bulletin, 2018.

Over the last 5000 years, Mount Taranaki volcano, located in the westernmost part of New Zealand’s North Island, produced at least 16 Plinian-scale explosive eruptions, the latest at AD 1655. These eruptions had magnitudes of 4 to 5, eruptive styles, and contrasting basaltic to andesitic chemical compositions comparable to the eruptions of Etna, 122 BC; Vesuvius, AD79; Tarawera, 1886; Pelée, 1902; Colima, 1910; Mount Saint Helens, 1980; Merapi, 2010; and Calbuco, 2015.

In this work, Rafael Torres-Orozco and colleagues combined geological mapping and lithostratigraphic analyses to define the possible hazard scenarios in case of Taranaki’s explosive reawakening.

The results indicate that, during a future Plinian event, bursting of both long-lasting, large-volume lava domes and transient, small-volume lava plugs from Taranaki’s andesitic summit crater would be typical, and these would produce different types of pyroclastic density currents (PDCs) flowing down the volcano flanks mainly due to gravity.

The most deadly “blast-type” PDCs would first explode and expand laterally, and then would flow downstream, reaching urban areas located at up to 18 km distance from the crater. Eruptive columns following or accompanying PDCs are ubiquitous to every scenario. These columns would inject ash and gas into the atmosphere, and could disperse 10-cm-thick layers of volcanic material over the most populated areas at 20-30 km from the crater. In the scenario of eruptions produced from vents different to the summit-crater, these would be expected to be basaltic and lack major PDCs.

These scenarios highlight the major role that PDCs must have in evaluating the hazardscape of Taranaki and of other similar volcanoes. The scenarios can be tailored to different sites around the world by localized studies, and can also be used to plan emergency management.

Reference:
Torres-Orozco et al. Volcanic hazard scenarios for multi-phase andesitic Plinian eruptions from lithostratigraphy: Insights into PDC diversity at Mount Taranaki, New Zealand. GSA Bulletin, 2018 DOI: 10.1130/G31850.1

Note: The above post is reprinted from materials provided by Geological Society of America.

Earth’s magnetic field is not about to reverse

Intensity at Earth's surface (left) and radial field (Br) at the CMB (right).
Intensity at Earth’s surface (left) and radial field (Br) at the CMB (right). Top: mid-point of the Laschamp excursion; bottom: mid-point of the Mono Lake excursion. The field is truncated at spherical harmonic degree five. Credit: University of Liverpool

A study of the most recent near-reversals of the Earth’s magnetic field by an international team of researchers, including the University of Liverpool, has found it is unlikely that such an event will take place anytime soon.

There has been speculation that the Earth’s geomagnetic fields may be about to reverse , with substantial implications, due to a weakening of the magnetic field over at least the last two hundred years, combined with the expansion of an identified weak area in the Earth’s magnetic field called the South Atlantic Anomaly, which stretches from Chile to Zimbabwe.

In a paper published in the Proceedings of the National Academy of Sciences, a team of international researchers model observations of the geomagnetic field of the two most recent geomagnetic excursion events, the Laschamp, approximately 41,000 years ago, and Mono Lake, around 34,000 years ago, where the field came close to reversing but recovered its original structure.

The model reveals a field structures comparable to the current geomagnetic field at both approximately 49,000 and 46,000 years ago, with an intensity structure similar to, but much stronger than, today’s South Atlantic Anomaly (SAA); their timing and severity is confirmed by records of cosmogenic nuclides. However, neither of these SAA-like fields developed into an excursion or reversal.

Richard Holme, Professor of Geomagnetism at the University of Liverpool, said: “There has been speculation that we are about to experience a magnetic polar reversal or excursion. However, by studying the two most recent excursion events, we show that neither bear resemblance to current changes in the geomagnetic field and therefore it is probably unlikely that such an event is about to happen.

“Our research suggests instead that the current weakened field will recover without such an extreme event, and therefore is unlikely to reverse.”

The strength and structure of the Earth’s magnetic field has varied at different times throughout geological history. At certain periods, the geomagnetic field has weakened to such an extent that it was able to swap the positions of magnetic north and magnetic south, whilst geographic north and geographic south remain the same.

Called a geomagnetic reversal, the last time this happened was 780,000 years ago. However, geomagnetic excursions, where the field comes close to reversing but recovers its original structure, have occurred more recently.

The magnetic field shields the Earth from solar winds and harmful cosmic radiation. It also aids in human navigation, animal migrations and protects telecommunication and satellite systems. It is generated deep within the Earth in a fluid outer core of iron, nickel and other metals that creates electric currents, which in turn produce magnetic fields.

Reference:
Maxwell Brown, Monika Korte, Richard Holme, Ingo Wardinski, Sydney Gunnarson. Earth’s magnetic field is probably not reversing. Proceedings of the National Academy of Sciences, 2018; 201722110 DOI: 10.1073/pnas.1722110115

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

Was the Earth ever frozen solid?

Snowball Earth
How “Snowball Earth” might have looked. Credit: NASA

The movie The Day After Tomorrow depicts a catastrophic climate shift to global cooling, which is referred to as the new ice age. In the movie, melting of polar ice caused by global warming disrupts the North Atlantic current, rapidly dropping the ocean temperature, ultimately leading to the freezing of the ocean on a global scale. Although this over-the-top effect portrayed by this fictional film contains little scientific truth, many scientists are studying a global ice age during the Cryogenian, a geologic period that lasted from 720 to 635 million years ago.

Recent research on glacial refugia has been heating up the debate about this ice age, brewing a contention over the extent to which the glaciation covered the Earth. Two main hypotheses are on the table: “Snowball Earth” theory, which argues that ice covered the entire Earth, and “Slushball Earth” hypothesis, where the band of the sea near the equator stayed open, allowing the hydrologic cycle—the evaporation and precipitation of water— to persist.

The term Snowball Earth was first coined by Joe Kirschvink, a geobiologist at CalTech in the late 1980s. The theory was based on the early observation that glacial deposits from this time were widely distributed on nearly every continent, with some geologic evidence even suggesting glaciation at tropical latitudes. The abrupt change in the climate is rooted in the positive feedback loop, commonly referred to as the albedo (“whiteness” in Latin) effect. Simply put, as Earth cools and ice forms from the pole down to lower latitudes, the albedo, or the whiteness of the Earth increases, reflecting more solar radiation—just like how a black t-shirt absorbs more heat, while a white t-shirt reflects all wavelengths of light.

Along with the albedo effect, the long-term carbon cycle kicked into high gear, making a double positive feedback. As the ancient supercontinent Rodinia broke apart, the newly created coastline in the low latitude intensified the weathering of the rock. Silicate rock, which constitutes the majority of the Earth’s crust, goes through a chemical weathering reaction that removes CO2 from the atmosphere. As the atmospheric CO2 was reduced, Earth became colder, as CO2, along with other greenhouse gases, blocks heat from escaping the Earth. Moreover, because the broken up continents were in the low latitudes, they could not have prevented the advance of ice that formed in the poles, the coldest region on Earth, which would have created a completely frozen planet.

The critics of the Snowball Earth theory—including professor Richard Peltier and his fellow colleagues at the University of Toronto and Texas A&M—published a paper refuting the hypothesis, in which they run a series of simulations that resulted in an equatorial belt of open water that may explain the survival of the organisms during the ice age, as well as the subsequent revival of numerous species.

Their argument stems from the fact that the process of glaciation not only entailed positive feedback, but also one important negative feedback. As the climate got colder, the atmospheric oxygen would have sunk deeper into the ocean. As atmospheric oxygen spread deep into the sea, it bonded with the layer of old organic matter, forming CO2. Carbon dioxide, released back into the atmosphere, would have warmed the Earth by the greenhouse effect, which would have defrosted Earth, stopping the ice sheets and glaciers from further advancing. Therefore, such negative feedback could have prevented ice from completely covering the Earth surface.

Peltier provides another key piece of evidence against Snowball Earth theory: a geographic region that allowed the survival of fauna and flora, referred to as the “glacial refugia.” Had the Earth completely frosted itself, its harsh climate would have killed off many organisms. Moreover, complete reflection of solar radiation would have decimated photosynthetic organisms. Yet, there is no such geological indication that a mass extinction event occurred.

The debate of hard versus slushy Snowball Earth becomes more enigmatic at the end of the Cryogenic period and start of Cambrian, when the so-called “Cambrian explosion” of animal life occurs. The Cambrian explosion refers to a short interval during which many multicellular animals in diverse forms appeared on the surface of the Earth. Critics of Snowball Earth argue that such a dramatic increase in biodiversity within a short period of time would not have been able to happen in a hard Snowball Earth scenario, as many organisms prior to the explosion would have gone extinct. The supporters of Snowball Earth, on the other hand, argue that the biodiversity is simply the result of the robust micro-organisms that survived the Snowball Earth, evolving in size as well as anatomical complexity through time.

Neither of these hypotheses is set in stone, but rather are part of an ongoing debate that requires much clarification. To better understand what happened during the Cryogenian period, developing different climate models with many parameters is necessary, giving flexibility to the ever-unknown complexity of past climate conditions. Moreover, careful study of the organisms that survived Snowball Earth could further assist our understanding of this enigmatic period.

Note: The above post is reprinted from materials provided by Earth Institute, Columbia University.

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