‘Permian-Triassic extinction killed plants first’


This March 2018 video says about itself:

The Great Dying’ Was Our Worst Extinction Ever, And It Could Happen Again

What exactly caused the greatest extinction on earth? New research may finally hold the answer to this long time mystery.

From the University of Nebraska-Lincoln in the USA:

Earth’s largest extinction event likely took plants first

January 31, 2019

Summary: New evidence from the cliffsides of Australia suggests that Earth’s largest extinction event — a volcanic cataclysm occurring roughly 252 million years ago — extinguished plant life long before many animal counterparts.

Little life could endure the Earth-spanning cataclysm known as the Great Dying, but plants may have suffered its wrath long before many animal counterparts, says new research led by the University of Nebraska-Lincoln.

About 252 million years ago, with the planet’s continental crust mashed into the supercontinent called Pangaea, volcanoes in modern-day Siberia began erupting. Spewing carbon and methane into the atmosphere for roughly 2 million years, the eruption helped extinguish about 96 percent of oceanic life and 70 percent of land-based vertebrates — the largest extinction event in Earth’s history.

Yet the new study suggests that a byproduct of the eruption — nickel — may have driven some Australian plant life to extinction nearly 400,000 years before most marine species perished.

“That’s big news”, said lead author Christopher Fielding, professor of Earth and atmospheric sciences. “People have hinted at that, but nobody’s previously pinned it down. Now we have a timeline.”

The researchers reached the conclusion by studying fossilized pollen, the chemical composition and age of rock, and the layering of sediment on the southeastern cliffsides of Australia. There they discovered surprisingly high concentrations of nickel in the Sydney Basin’s mud-rock — surprising because there are no local sources of the element.

Tracy Frank, professor and chair of Earth and atmospheric sciences, said the finding points to the eruption of lava through nickel deposits in Siberia. That volcanism could have converted the nickel into an aerosol that drifted thousands of miles southward before descending on, and poisoning, much of the plant life there. Similar spikes in nickel have been recorded in other parts of the world, she said.

“So it was a combination of circumstances,” Fielding said. “And that’s a recurring theme through all five of the major mass extinctions in Earth’s history.”

If true, the phenomenon may have triggered a series of others: herbivores dying from the lack of plants, carnivores dying from a lack of herbivores, and toxic sediment eventually flushing into seas already reeling from rising carbon dioxide, acidification and temperatures.

‘It Lets Us See What’s Possible’

One of three married couples on the research team, Fielding and Frank also found evidence for another surprise. Much of the previous research into the Great Dying — often conducted at sites now near the equator — has unearthed abrupt coloration changes in sediment deposited during that span.

Shifts from grey to red sediment generally indicate that the volcanism’s ejection of ash and greenhouse gases altered the world’s climate in major ways, the researchers said. Yet that grey-red gradient is much more gradual at the Sydney Basin, Fielding said, suggesting that its distance from the eruption initially helped buffer it against the intense rises in temperature and aridity found elsewhere.

Though the time scale and magnitude of the Great Dying exceeded the planet’s current ecological crises, Frank said the emerging similarities — especially the spikes in greenhouse gases and continuous disappearance of species — make it a lesson worth studying.

“Looking back at these events in Earth’s history is useful because it lets us see what’s possible,” she said. “How has the Earth’s system been perturbed in the past? What happened where? How fast were the changes? It gives us a foundation to work from — a context for what’s happening now.”

The researchers detailed their findings in the journal Nature Communications. Fielding and Frank authored the study with Allen Tevyaw, graduate student in geosciences at Nebraska; Stephen McLoughlin, Vivi Vajda and Chris Mays from the Swedish Museum of Natural History; Arne Winguth and Cornelia Winguth from the University of Texas at Arlington; Robert Nicoll of Geoscience Australia; Malcolm Bocking of Bocking Associates; and James Crowley of Boise State University.

The National Science Foundation and the Swedish Research Council funded the team’s work.

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Edaphosaurus, ancient sail-backed mammal-like reptile


This 28 January 2019 video says about itself:

Edaphosaurus, meaning “pavement lizard” for dense clusters of teeth) is a genus of extinct edaphosaurid synapsid. It lived in what is now North America and Europe around 300 to 280 million years ago, during the late Carboniferous to early Permian periods.

Edaphosaurus is important as one of the earliest known large plant-eating (herbivorous) amniote tetrapods (four-legged land-living vertebrates). In addition to the large tooth plates in its jaws, the most characteristic feature of Edaphosaurus is a sail on its back which is unique in shape and morphology. Edaphosaurus species measured from 0.5 metres (1.6 ft) to almost 3.5 metres (11.5 ft) in length and weighed over 300 kilograms (660 lb).

Like its more famous relative Dimetrodon, Edaphosaurus had a sail-like fin that was supported by bones of the vertebral column. Edaphosaurus differs from Dimetrodon in having cross-bars on the spines that supported its fin. Edaphosaurus and other members of the Edaphosauridae evolved tall dorsal sails independently of sail-back members of the Sphenacodontidae. Dimetrodon and Secodontosaurus that lived at the same time are an unusual example of parallel evolution.

How an ancient amphibian moved, video


This 16 January 2019 video says about itself:

Watch researchers re-create how an early tetropod moved | Science News

To examine possible gaits for Orobates pabsti, a creature that lived 290 million years ago, researchers used a robot (dubbed the OroBOT) as well as digital simulations of different walking styles. Here, scientists watch as OroBOT struts its stuff, moving forward without much side-to-side undulation and with relatively erect legs that hold its belly off the ground. Using a digital simulation (top) and the OroBOT (bottom), the researchers [reconstruct] the footprint pattern left by O. pabsti using an erect, non-undulating gait.

By Carolyn Gramling, 1:27pm, January 16, 2019:

A four-legged robot hints at how ancient tetrapods walked

Orobates pabsti may have had a more developed gait that previously thought

Orobates pabsti lived between 280 million and 290 million years ago, but it was pretty advanced at doing the locomotion.

Using computer simulations, re-created skeletons, fossil trackways and a walking robot dubbed the OroBOT, scientists found that this ancient four-footed creature had a surprisingly efficient gait. The result suggests that developing a more advanced way of walking may not have been as closely linked to the later diversification of tetrapods as once thought, the researchers report January 17 in Nature.

Scientists care about how O. pabsti might have moved because the animal was one of the earliest amniotes,

There is disagreement among scientists whether Diadectids, the family to which Orobates belonged, were ‘already’ amniotes or ‘still’ amphibians.

a group that arose around 350 million years ago and includes both reptiles and mammals. Unlike amphibians, which have aquatic young, amniotes can live entirely on land. Protective membranes surrounding embryos allow amniotes to bypass a tadpole-type life stage in water: Reptile (including bird) eggs can be laid on land in nests; mammal embryos stay within the mother.

The amniotic membrane “is regarded as a key evolutionary innovation, to be able to colonize different habitats,” says John Nyakatura, a paleontologist at the Humboldt University of Berlin who led the new study.

Understanding how early amniotes walked on land could help scientists better understand the origins of amniotes themselves, and how they eventually diversified across the continents, Nyakatura says. “Orobates, our focus fossil in this story, is a very close cousin to the last common ancestor of mammals and reptiles,” he says.

Researchers first described O. pabsti in 2004, following the discovery of beautifully preserved fossils of the creature at a site in central Germany known as the Bromacher locality. “The preservation is phenomenal,” says Stuart Sumida, a vertebrate paleontologist at California State University, San Bernardino who was not involved in the new study. “These are things preserved from the tip of the nose to the tip of the tails,” Sumida says. “They are so well preserved that we can generate hypotheses about how they moved.”

Then, a few years later, researchers linked the creatures to a series of footprints, called a trackway, found at the same locality, offering more clues to how the animal might have walked.

STEP BY STEP In 2007, scientists determined that these fossil trackways were made by Orobates pabsti. Both a fossil skeleton and these trackways were essential to a new study’s analysis of how O. pabsti might have walked. Photo Sebastian Voigt/Urweltmuseum Geoskop Thallichtenberg

In 2007, scientists determined that these fossil trackways were made by Orobates pabsti. Both a fossil skeleton and these trackways were essential to a new study’s analysis of how O. pabsti might have walked.

But there’s more to visualizing walking than knowing where an animal put its feet. Various approaches are used to study the locomotion of extinct animals, including examining their anatomy from fossils, studying trackways (SN: 1/30/10, p. 9) or even building robots, says study coauthor Kamilo Melo, a bioroboticist at École Polytechnique Fédérale de Lausanne in Switzerland. But what’s different about the new study, Melo says, is that the scientists have combined several of these tactics to get the best possible approximation of an ancient creature’s gait.

The researchers first re-created the skeleton of the creature and used it to constrain the possible ranges of motion of arms and legs, called a kinematic simulation. “You create a marionette, and see what amount of angle each joint can move,” Melo says. And the scientists created a dynamic simulation, which included factors such as gravity, friction and balance, to really examine how the animal might have walked.

The team also looked to modern four-footed species, including salamanders, skinks, caimans and iguanas, to examine possible ranges of motion for tetrapods. Skinks and salamanders, for example, hold their bodies lower with their limbs more sprawled out to the side while caimans tend have more erect limbs.

Finally, the scientists created a tetrapod robot, dubbed the OroBOT, to act out potential gaits and match the prints they’d create to the fossil tracks. The researchers ultimately considered 512 different possible types of movement, scoring them on scales such as energy consumption, balance and precision — how well the gait reproduces the fossil tracks without slipping or sliding. (The researchers have also put their digital simulation online; try out different gaits here.)

The data suggest that O. pabsti had a relatively advanced style of walking, one that researchers previously thought would have belonged to later tetrapods. It held its belly off the ground, and had a stable, efficient gait without a lot of side-to-side, salamander-like undulations. That style of walking probably helped the animal conserve energy.

Sumida praises the study’s multipronged design, which allowed the scientists to test their findings in multiple ways, from fossil to digital simulations to robot. Furthermore, he notes, the team’s biomechanical analysis has confirmed something that previously was strongly suspected only by the fossil’s finders: that O. pabsti was indeed a fully terrestrial animal that probably had a relatively modern gait.

Sumida and others have demonstrated that amniotes from the same locality were using a range of different walking styles. Some had erect limbs like O. pabsti, some sprawled, and at least one animal walked on two legs. “What these studies are showing is that when amniotes first showed up, they were doing lots of things more quickly than we ever realized,” he says.

The findings are just a start, Nyakatura says. The researchers hope their multipronged approach will be a jumping-off point, not only for scientists to better understand O. pabsti, but also to examine other ancient locomotive puzzles, such as the evolution of active flight, bipedal locomotion in human ancestors and the transition from terrestrial to aquatic in marine mammals. “We have a whole bag of interesting things to study,” he says.

Plant survivors of Permian-Triassic mass extinction


This 26 February 2018 video from the USA says about itself:

The Permian-Triassic Boundary – The Rocks of Utah

The Great Dying! In this episode we head out to the Permian-Triassic boundary and try to discover what caused Earth’s Largest mass extinction event, 252 million years ago.

After 4-months of research, I’m excited to finally release this exciting video! A pre-print of the scientific paper is available here.

I’ve submitted this research to the journal “Global and Planetary Change” for peer review.

By Laurel Hamers, 2:12pm, December 20, 2018:

More plants survived the world’s greatest mass extinction than thought

Fossils in a Jordanian desert reveal plant lineages that didn’t perish in the Great Dying

Some ancient plants were survivors.

A collection of roughly 255-million-year-old fossils suggests that three major plant groups existed earlier than previously thought, and made it through a mass extinction that wiped out more than 90 percent of Earth’s marine species and roughly 70 percent of land vertebrates.

The fossils, described in the Dec. 21 Science, push back the earliest records of these plant groups by about 5 million years. “But it’s not just any 5 million years — it’s those 5 million years that span the Permian-Triassic boundary”, says study coauthor Benjamin Bomfleur, a paleobotanist at the University of Münster in Germany. The find adds to the growing list of land plants that survived the catastrophe known as the Great Dying, the world’s greatest mass extinction, which occurred about 252 million years ago at the end of the Permian Period.

Bomfleur and his colleagues found the new fossils in desert rock outcroppings near the Dead Sea in Jordan. Paleontologists have been searching those rock formations for decades. “Every time we go, we find new fossils”, he says.

At the time these fossils formed, the area had a tropical climate but with prolonged dry periods. Those conditions aren’t good for forming fossils. But surprisingly, these fossils are exceptionally well preserved, Bomfleur says. He and his colleagues were able to wash the rocks with an acid to extract waxy plant cuticles embedded within. The cuticle preserves a mold of microscopic features on the surfaces of fronds or leaves, and those details helped the scientists identify the plant species more accurately.

The team found fossils belonging to the Podocarpacae family, a large group of cone-bearing plants that now live in the Southern Hemisphere. It’s the oldest fossil evidence from any family of conifers that still exists today.

And the fossils showed that two other major seed plant lineages that are now extinct — Bennettitales and Corystospermales — were around during the Permian and survived the die-off. The Bennettitales are particularly noteworthy because they produce flowerlike reproductive structures and might have been distant cousins to flowering plants, which first showed up about 125 million years ago.

Today, the tropics are hot spots for biodiversity, and it’s thought that the ancient tropics were too. But there’s very little fossil evidence, says Fabiany Herrera, a paleobotanist at the Chicago Botanic Garden. Based on previous genetic analyses, it would make sense for some of these ancient tropical plant groups to have survived the mass extinction. “But we had no fossils”, Herrera says — and that’s the only way to know for sure. “Now we have them.”

Permian era animals, how big?


This June 2018 video says about itself:

Permian Creatures Size Comparison. Paleoart

SPECIES: Diictodon / Mesosaurus / Procynosuchus / Estemmenosuchus / Titanopheus / Scutosaurus / Edaphosaurus / Dimetrodon / Cotylorhynchus / Moschops / Anteosaurus / Inostrancevia / Prionosuchus.

Permian-Triassic mass extinction by global warming


This July 2018 video says about itself:

252 million years ago 96% of all marine species and 70% of terrestrial vertebrate species vanished, this was the Permian extinction.

From the University of Washington in the USA:

Biggest mass extinction caused by global warming leaving ocean animals gasping for breath

December 6, 2018

Summary: By combining ocean models, animal metabolism and fossil records, researchers 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 their survival.

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.

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.

The study is published in the Dec. 7 issue of Science.

“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.

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.

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.”

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.”

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.”

Ancient Mesosaurus reptiles, aquatic or semi-aquatic?


This 2015 video says about itself:

“Mesosaurs” were a group of small aquatic reptiles that lived during the early Permian period, roughly 299 to 270 million years ago. Mesosaurs were the first aquatic reptiles, having apparently returned to an aquatic lifestyle from more terrestrial ancestors. However, just how terrestrial mesosaur ancestors had become remains uncertain; recent research cannot establish with confidence if the first amniotes were fully terrestrial, or only amphibious.

From Frontiers in Ecology and Evolution:

Oldest-known aquatic reptiles probably spent time on land

September 19, 2018

The oldest known aquatic reptiles, the mesosaurs, probably spent part of their life on land, reveals a new study published in Frontiers in Ecology and Evolution. The fossilized bones of adult Mesosaurus share similarities with land-dwelling animals, which — coupled with the relative scarcity of land-weathered fossilized remains of large specimens — suggests that older mesosaurs were semi-aquatic, whereas juveniles spent most of their time in the water. This new research emphasizes the importance of thoroughly analyzing fossilized remains from across all stages of a reptile’s life to get a full appreciation of its lifestyle and behavior.

“Despite being considered the oldest-known fully aquatic reptile, mesosaurs share several anatomical features with terrestrial species”, says Professor Graciela Piñeiro, who completed this research at the Facultad de Ciencias, Universidad de la República, Uruguay. “Our comprehensive analysis of the vertebrae and limbs of these ancient reptiles suggests they lived in the water during the earliest stages of their development, whereas mature adults spent more time on land.”

Since the discovery of unusually large Mesosaurus bones in the Mangrullo Formation of Uruguay, Piñeiro and her international team of colleagues wondered why the larger, presumably adult specimens, around two meters in length, were not as abundant as mesosaur skeletons of around 90 cm.

“The larger specimens, at least twice the length of the more commonly reported Mesosaurus fossils, could just be exceptionally big individuals. However, the environmental conditions of the Mangrullo lagoon of where they lived were harsh, making it difficult for the occasional mesosaur to reach such a relatively large size and age”, explains Piñeiro.

She continues, “We then realized that in comparison to the smaller, better-preserved specimens, larger Mesosaurus fossils were almost always disarticulated, very weathered and badly preserved. This suggested these larger specimens had extended exposure to the air when they died.”

During the reconstruction of a Mesosaurus skeleton and analysis of skeletons representing different life stages of this ancient reptile, the researchers examined the remains for evidence of a terrestrial, land-dwelling existence.

Terrestrial, semi-aquatic and aquatic animals show a clear difference in bone profiles, so they used morphometrics to analyze the shape of the fossilized bones. Forty Mesosaurus specimens, from juveniles to adults, were examined and their bone profiles compared to those of similar reptiles known to be aquatic or semi-aquatic, such as crocodiles and marine iguanas.

“The adult mesosaur tarsus (a cluster of bones in the ankle region) suggests a more terrestrial or amphibious locomotion rather than a fully aquatic behavior as widely suggested before”, says Pablo Núñez, also based at Universidad de la República. “Their caudal vertebrae, the tail bones, also showed similarities to semi-aquatic and terrestrial animals. This supports the hypothesis that the oldest and largest mesosaurs spent more time on land, where fossil preservation is not as good as in the subaquatic domain.”

Published as part of a special article collection on Mesosaurs, these findings have broader implications — both for future research on early prehistoric animals that laid eggs with embryonic membranes and for the understanding of reptile evolution.

Piñeiro explains, “Our study emphasizes the importance of working with fossils representing an entire population of a species, including a wide range of juveniles and adults, before establishing paleobiological interpretations on their lifestyle and behavior.”

She continues, “These findings also have important implications on the inferred lifestyle of species closely related to mesosaurs, particularly in the context of the evolution of the amniotic egg. For instance, thanks to our previous discovery of a mesosaur egg and embryos inside the mother’s body, our new findings can give support to earlier hypotheses suggesting that the amniotic egg might have appeared in aquatic or semiaquatic animals as a strategy to leave the water to avoid predation.”