New research undertaken by scientists at the Smithsonian National Museum of Natural History, Royal Ontario Museum (ROM) and University of Montreal, has uncovered fossils of a new species of marine animal, Gyaltsenglossus senis, (pronounced Gen-zay-gloss-us senis) that provides new evidence in the historical debate among zoologists: how the anatomies of the two main types of an animal group called the hemichordates are related. The fossils are over half-a-billion years old and were discovered at a Burgess Shale site in the Canadian Rockies. This discovery was published August 27, 2020, in the science journal Current Biology.

With the early evolution of hemichordates being contentious among researchers the discovery of Gyaltsenglossus senis is significant. It provides direct fossil evidence connecting the two major groups of hemichordates: the enteropneusta and pterobranchia.

Although enteropneusts and pterobranchs appear to be quite different types of animals they are closely related. This close relationship is supported by DNA analysis of present-day species. More broadly, the role of Gyaltsenglossus in understanding hemichordate evolution helps us understand the origins of a larger group of animals called deuterostomes (which includes humans) by clarifying what characteristics they may have shared with hemichordates early in their history.

The enteropneusta are a group of animals known commonly as acorn worms, which are long, mostly mud-burrowing animals, that can be found today in oceans around the world from the tropics to Antarctic. The other main group of animals within hemichordates are pterobranchs, which are microscopic animals that live in colonies, each protected by tubes they construct and which feed on plankton using a crown of tentacled arms.

“Acorn worms and pterobranchs look so different from each other that understanding the origins of their evolutionary relationship has been a major historical question in zoology,” said Dr. Karma Nanglu, Peter Buck Deep Time post-doctoral fellow at the Smithsonian National Museum of Natural History and lead author on this paper. “Answering this question has been made much harder by the extreme lack of fossils of these soft-bodied hemichordates. Throughout the half-billion-year-long history of hemichordates you can count on one hand the number of exceptional preserved fossil species.”

Despite being just two centimeters in length, the remarkably preserved soft tissues of the Gyaltsenglossus fossils reveal incredibly detailed anatomical structures. These details include the oval-shaped proboscis of acorn worms and a basket of feeding tentacles similar to those of pterobranchs. The age of these fossils, combined with the unique morphological combination of the two major hemichordate groups, makes this discovery a critical find for understanding early hemichordate evolution.

“An ancient animal with an intermediary anatomy between acorn worms and pterobranchs had been hypothesized before but this new animal is the clearest view of what the ancestral hemichordate may have looked like,” says Dr. Christopher Cameron, Associate Professor at the University of Montreal and a co-author on this study. “It’s exciting to have so many new anatomical details to help drive new hypotheses about hemichordate evolution.”

In the case of Gyaltsenglossus, the exceptional preservation of these fine details can be attributed to the unique environmental conditions of the Burgess Shale, which rapidly entombed ancient animals in underwater mudslides. Through a combination of factors, including slowing the rate of bacteria decaying the entombed animals’ bodies, the fossils of the Burgess Shale are preserved with far greater fidelity than typical fossil sites.

“The Burgess Shale has been pivotal in understanding early animal evolution since its discovery over 100 years ago,” says co-author Dr. Jean-Bernard Caron, Richard M. Ivey Curator of Invertebrate Palaeontology at the ROM and Associate Professor at the University of Toronto. Dr. Caron led the field expedition in 2010 which collected the 33 fossils of Gyaltsenglossus.

“In most localities, you would be lucky to have the hardest parts of animals, like bones and teeth, preserved, but at the Burgess Shale even the softest body parts can be fossilized in exquisite detail,” says Dr. Caron. “This new species underscores the importance of making new fossil discoveries to shine light on the most stubborn evolutionary mysteries.”

In this particular case, Gyaltsenglossus suggests that the ancestral hemichordate may have been able to use the feeding strategies of both of the modern groups. Like acorn worms, the long proboscis may have been used to feed on nutrient-filled marine mud, while at the same time, and like the pterobranchs, the array of six feeding arms was probably used to grab suspended food particles directly from the water above where it was crawling.

Hemichordates belong to a major division of animal life called Deuterostomia, which includes chordates like fish and mammals, and not the division of animal life called Protostomia, that includes arthropods such as insects and annelids such as earthworms. Dr. Nanglu explains, when looking at Gyaltsenglossus, we’re actually looking at a very, very distant relative of our own branch of vertebrate and human evolution.

“The close relationship between hemichordates and our own evolutionary group, the chordates, is one of the first things that made me excited to research them,” Nanglu explains. “Understanding the ancient connections that join animals like fish and even humans to their distant cousins like sea urchins and acorn worms is such an interesting area on the evolutionary tree and Gyaltsenglossus helps bring that link into focus a little bit more clearly.”

The original 1909 discovery and research about the Burgess Shale was made by Charles Walcott, who was Secretary of the Smithsonian Institution at the time. The Burgess Shale fossil sites are located within Yoho and Kootenay National Parks and are managed by Parks Canada.

Reference:
Cambrian Tentaculate Worms and the Origin of the Hemichordate Body Plan . Current Biology (2020). DOI: 10.1016/j.cub.2020.07.078

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

About 25 years ago, researchers discovered the first dinosaur embryos in an enormous nesting ground of titanosaurian dinosaurs that lived about 80 million years ago in a place known as Auca Mahuevo in Patagonia, Argentina. Now, researchers reporting in the journal Current Biology on August 27 describe the first near-intact embryonic skull. The finding adds to our understanding of the development of sauropod dinosaurs, a group characterized by the long neck and tails and small heads perhaps most familiar in the Brontosaurus, and suggests that they may have had specialized facial features as hatchlings that changed as they grew into adults.

“The specimen studied in our paper represents the first 3-D preserved embryonic skull of a sauropod sauropodomorph,” says Martin Kundrat of the PaleoBioImaging Lab at Pavol Jozef Šafárik University, Slovak Republic. “The most striking feature is head appearance, which implies that hatchlings of giant dinosaurs may differ in where and how they lived in their earliest stages of life. But because it differs in facial anatomy and size from the sauropod embryos of Auca Mahuevo, we cannot rule out that it may represent a new titanosaurian dinosaur.”

The new embryonic dinosaur specimen also is from Patagonia, although its precise origin isn’t known. That’s because the egg was illegally exported from the country and brought to researchers’ attention only later. When Terry Manning, a co-author on the study from Arizona, realized the unique preservation and scientific importance of the specimen, he agreed to send this unique fossil back to Argentina for further study. It’s now housed with other titanosaurian embryos from Auca Mahuevo under curation of Rodolfo Coria at the Museo Municipal Carmen Funes in Plaza Huincul.

In the new study, Kundrat’s team used a new imaging technology called synchrotron microtomography to study the inner structure of bones, teeth, and soft tissues of the embryonic dinosaur. The scans allowed Kundrat and co-author Daniel Snitting, Uppsala University, Sweden, to find hidden details, including tiny teeth preserved deeply in tiny jaw sockets. They also found partly calcified elements of the embryonic braincase and what appear to be the remains of temporal muscles.

The scans allowed the researchers to reconstruct the most plausible appearance of the skull in titanosaurian sauropods before hatching. Those details are useful for taxonomic or developmental comparisons among related dinosaurs.

The findings also suggest that the baby sauropods may have hatched out of the egg with the help of a thickened prominence rather than a boney “egg-tooth.” They uncovered evidence as well that the embryonic dinosaurs used calcium derived from the eggshell long before they were ready to hatch.

They report that the titanosaurian hatchlings emerged with a temporary moncerotid (single-horned) face. They also had retracted openings on the nose (nares) and early binocular vision. “We suggest an alternative head appearance for babies of these Patagonian giants,” Kundrat says.

The findings suggest that the young sauropods had a specialized head and face that transformed as the young dinosaurs grew and matured into adults. The findings have implications for our understanding of the dinosaurs and how they lived, the researchers say. “Dinosaur eggs are for me like time capsules that bring a message from the ancient time,” Kundrat says. “This was the case of our specimen that tells a story about Patagonian giants before they hatched.

“Our study revealed several new aspects about the embryonic life of the largest herbivorous dinosaurs that lived on our planet,” he adds. “A horned faced and binocular vision are features quite different from what we expected in titanosaurian dinosaurs.”

Kundrat says he’ll continue to study embryonic dinosaurs from other continents using the synchrotron technology.

Reference:
Current Biology, Kundrat et al.: “Specialized Craniofacial Anatomy of a Titanosaurian Embryo from Argentina” DOI: 10.1016/j.cub.2020.07.091

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

Hibernation is a familiar feature on Earth today. Many animals — especially those that live close to or within polar regions — hibernate to get through the tough winter months when food is scarce, temperatures drop and days are dark.

According to new research, this type of adaptation has a long history. In a paper published Aug. 27 in the journal Communications Biology, scientists at the University of Washington and its Burke Museum of Natural History and Culture report evidence of a hibernation-like state in an animal that lived in Antarctica during the Early Triassic, some 250 million years ago.

The creature, a member of the genus Lystrosaurus, was a distant relative of mammals. Antarctica during Lystrosaurus’ time lay largely within the Antarctic Circle, like today, and experienced extended periods without sunlight each winter.

The fossils are the oldest evidence of a hibernation-like state in a vertebrate animal, and indicates that torpor — a general term for hibernation and similar states in which animals temporarily lower their metabolic rate to get through a tough season — arose in vertebrates even before mammals and dinosaurs evolved.

“Animals that live at or near the poles have always had to cope with the more extreme environments present there,” said lead author Megan Whitney, a postdoctoral researcher at Harvard University who conducted this study as a UW doctoral student in biology. “These preliminary findings indicate that entering into a hibernation-like state is not a relatively new type of adaptation. It is an ancient one.”

Lystrosaurus lived during a dynamic period of our planet’s history, arising just before Earth’s largest mass extinction at the end of the Permian Period — which wiped out about 70% of vertebrate species on land — and somehow surviving it. The stout, four-legged foragers lived another 5 million years into the subsequent Triassic Period and spread across swathes of Earth’s then-single continent, Pangea, which included what is now Antarctica.

“The fact that Lystrosaurus survived the end-Permian mass extinction and had such a wide range in the early Triassic has made them a very well-studied group of animals for understanding survival and adaptation,” said co-author Christian Sidor, a UW professor of biology and curator of vertebrate paleontology at the Burke Museum.

Paleontologists today find Lystrosaurus fossils in India, China, Russia, parts of Africa and Antarctica. These squat, stubby, creatures — most were roughly pig-sized, but some grew 6 to 8 feet long — had no teeth but bore a pair of tusks in the upper jaw, which they likely employed to forage among ground vegetation and dig for roots and tubers, according to Whitney.

Those tusks made Whitney and Sidor’s study possible. Like elephants, Lystrosaurus tusks grew continuously throughout their lives. The cross-sections of fossilized tusks can harbor life-history information about metabolism, growth and stress or strain. Whitney and Sidor compared cross-sections of tusks from six Antarctic Lystrosaurus to cross-sections of four Lystrosaurus from South Africa.

Back in the Triassic, the collection sites in Antarctica were at about 72 degrees south latitude — well within the Antarctic Circle, at 66.3 degrees south. The collection sites in South Africa were more than 550 miles north during the Triassic at 58-61 degrees south latitude, far outside the Antarctic Circle.

The tusks from the two regions showed similar growth patterns, with layers of dentine deposited in concentric circles like tree rings. But the Antarctic fossils harbored an additional feature that was rare or absent in tusks farther north: closely-spaced, thick rings, which likely indicate periods of less deposition due to prolonged stress, according to the researchers.

“The closest analog we can find to the ‘stress marks’ that we observed in Antarctic Lystrosaurus tusks are stress marks in teeth associated with hibernation in certain modern animals,” said Whitney.

The researchers cannot definitively conclude that Lystrosaurus underwent true hibernation — which is a specific, weeks-long reduction in metabolism, body temperature and activity. The stress could have been caused by another hibernation-like form of torpor, such as a more short-term reduction in metabolism, according to Sidor.

Lystrosaurus in Antarctica likely needed some form of hibernation-like adaptation to cope with life near the South Pole, said Whitney. Though Earth was much warmer during the Triassic than today — and parts of Antarctica may have been forested — plants and animals below the Antarctic Circle would still experience extreme annual variations in the amount of daylight, with the sun absent for long periods in winter.

Many other ancient vertebrates at high latitudes may also have used torpor, including hibernation, to cope with the strains of winter, Whitney said. But many famous extinct animals, including the dinosaurs that evolved and spread after Lystrosaurus died out, don’t have teeth that grow continuously.

“To see the specific signs of stress and strain brought on by hibernation, you need to look at something that can fossilize and was growing continuously during the animal’s life,” said Sidor. “Many animals don’t have that, but luckily Lystrosaurus did.”

If analysis of additional Antarctic and South African Lystrosaurus fossils confirms this discovery, it may also settle another debate about these ancient, hearty animals.

“Cold-blooded animals often shut down their metabolism entirely during a tough season, but many endothermic or ‘warm-blooded’ animals that hibernate frequently reactivate their metabolism during the hibernation period,” said Whitney. “What we observed in the Antarctic Lystrosaurus tusks fits a pattern of small metabolic ‘reactivation events’ during a period of stress, which is most similar to what we see in warm-blooded hibernators today.”

If so, this distant cousin of mammals isn’t just an example of a hearty creature. It is also a reminder that many features of life today may have been around for hundreds of millions of years before humans evolved to observe them.

The research was funded by the National Science Foundation.

Reference:
Megan R. Whitney, Christian A. Sidor. Evidence of torpor in the tusks of Lystrosaurus from the Early Triassic of Antarctica. Communications Biology, 2020; 3 (1) DOI: 10.1038/s42003-020-01207-6

Note: The above post is reprinted from materials provided by University of Washington. Original written by James Urton.

Paleontological research has confirmed a series of recently discovered fossils tracks are the oldest recorded tracks of their kind to date within Grand Canyon National Park. In 2016, Norwegian geology professor, Allan Krill, was hiking with his students when he made a surprising discovery. Lying next to the trail, in plain view of the many hikers, was a boulder containing conspicuous fossil footprints. Krill was intrigued, and he sent a photo to his colleague, Stephen Rowland, a paleontologist at the University of Nevada Las Vegas.

The trailside tracks have turned out to be even more significant than Krill first imagined. “These are by far the oldest vertebrate tracks in Grand Canyon, which is known for its abundant fossil tracks” says Rowland. “More significantly,” he added, “they are among the oldest tracks on Earth of shelled-egg-laying animals, such as reptiles, and the earliest evidence of vertebrate animals walking in sand dunes.”

The track-bearing boulder fell from a nearby cliff-exposure of the Manakacha Formation. The presence of a detailed geologic map of the strata along the Bright Angel Trail, together with previous studies of the age of the Manakacha Formation, allowed the researchers to pin down the age of the tracks quite precisely to 313 +/- 0. 5 million years.

The newly discovered tracks record the passage of two separate animals on the slope of a sand dune. Of interest to the research team is the distinct arrangement of footprints. The researchers’ reconstruction of this animal’s footfall sequence reveals a distinctive gait called a lateral-sequence walk, in which the legs on one side of the animal move in succession, the rear leg followed by the foreleg, alternating with the movement of the two legs on the opposite side. “Living species of tetrapods―dogs and cats, for example―routinely use a lateral-sequence gait when they walk slowly,” says Rowland. “The Bright Angel Trail tracks document the use of this gait very early in the history of vertebrate animals. We previously had no information about that.” Also revealed by the trackways is the earliest-known utilization of sand dunes by vertebrate animals.

Reference:
Stephen M. Rowland, Mario V. Caputo, Zachary A. Jensen. Early adaptation to eolian sand dunes by basal amniotes is documented in two Pennsylvanian Grand Canyon trackways. PLOS ONE, 2020; 15 (8): e0237636 DOI: 10.1371/journal.pone.0237636

Note: The above post is reprinted from materials provided by National Park Service.

A re-analysis of fossils from one of Europe’s most significant paleontological sites reveals a wide diversity of animal species, including a large terrestrial monkey, short-necked giraffe, rhinos and saber-toothed cats.

These and other species roamed the open grasslands of Eastern Europe during the early Pleistocene, approximately 2 million years ago. Ultimately, the researchers hope the fossils will provide clues about how and when early humans migrated to Eurasia from Africa. Reconstructions of past environments like this also could help researchers better understand future climate change.

“My colleagues and I are excited to draw attention back to the fossil site of Grăunceanu and the fossil potential of the Olteţ River Valley of Romania,” said Claire Terhune, associate professor of anthropology at the University of Arkansas. “It’s such a diverse faunal community. We found multiple animals that hadn’t been clearly identified in the area before, and many that are no longer found in Europe at all. Of course, we think these findings alone are interesting, but they also have important implications for early humans moving into the continent at that time.”

About 124 miles west of the Romanian capital of Bucharest, the Olteţ River Valley, including the the important site of Grăunceanu, is one of Eastern Europe’s richest fossil deposits. Many Olteţ Valley fossil sites, including Grăunceanu, were discovered in the 1960s after landslides caused in part by deforestation due to increased agricultural activity in the area.

Archeologists and paleontologists from the Emil Racoviţă Institute of Speleology in Bucharest excavated the sites soon after they were discovered. Fossils were recovered and stored at the institute, and scholarly publications about the sites flourished in the 1970s and 1980s. But interest in these fossils and sites waned over the past 20 to 30 years, in part because many records of the excavations and fossils were lost.

Since 2012, the international team, including Terhune and researchers from Romania, the United States, Sweden and France, has focused on this important fossil region. Their work has included extensive identification of fossils at the institute and additional field work.

In addition to the species mentioned above, the researchers identified fossil remains of animals similar to modern-day moose, bison, deer, horse, ostrich, pig and many others. They also identified a fossil species of pangolin, which were thought to have existed in Europe during the early Pleistocene but had not been solidly confirmed until now. Today, pangolins, which look like the combination of an armadillo and anteater and are among the most trafficked animals in the world, are found only in Asia and Africa.

Reference:
Claire E. Terhune, Sabrina Curran, Roman Croitor, Virgil Drăgușin, Timothy Gaudin, Alexandru Petculescu, Chris Robinson, Marius Robu, Lars Werdelin. Early Pleistocene fauna of the Olteţ River Valley of Romania: Biochronological and biogeographic implications. Quaternary International, 2020; DOI: 10.1016/j.quaint.2020.06.020

Note: The above post is reprinted from materials provided by University of Arkansas. Original written by Matt McGowan.

While paleontologists have a wealth of vertebrate fossils at their disposal, their knowledge of the ecology of ancient extinct species, particularly regarding their relationship with invertebrate species, is relatively poor. As bones and hard shells “fossilize” much better than soft tissues and cartilage, scientists are limited in their ability to infer the presence of parasitic or symbiotic organisms living in or on these ancient vertebrates. As a result, relatively little is known about the evolutionary relationships between these ancient “clades” and their modern descendants.

All hope is not lost, though, as researchers can infer the presence of these small organisms from the footprints they left behind. These records are called trace fossils, or ichnofossils. One clear example of such ichnofossils is the boreholes that many mollusks make in the turtle shell remains and whale and fish bones on the ocean floor. However, to this date, there have been no indications that such species also lived in the shell while the turtle was alive and well.

In their recent study published in the journal Palaios, Assistant Professor Kei Sato from Waseda University and Associate Professor Robert G Jenkins from Kanazawa University focused on the trace evidence left on the carapace (shell) of an extinct basal leatherback marine turtle (Mesodermochelys sp.). The fossil was recovered from an Upper Cretaceous formation in Nio River, Japan, and the evidence in question were 43 tiny, flask-shaped boreholes all over the turtle shell fossil.

Eager to learn more about the organisms responsible for this, the scientists formulated a hypothesis, based on previous borehole evidence found on ancient marine turtle shells. After observing the fossil up close and measuring the morphological characteristics of the boreholes, they produced a 3-dimensional reconstruction of the carapace and the cross-section of one of the boreholes, which allowed them to observe the intricate details left by the species.

Sato, who is the lead author of this study, elaborates on the surprising evidence they found, “We saw that there were signs of healing around the mouth of boreholes, suggesting that the turtle was alive when the organisms settled on the carapace.” Based on the morphology and positioning of the boreholes, they determined that the likely culprits for these boreholes were “bivalves” from the superfamily Pholadoidea, creatures similar to the modern clams. These “sessile” (or immobile) organisms normally require a stable substrate to bore into, and the turtle carapace was a suitable host. The fact that the host animal was swimming around freely probably helped, as this allowed exposure to new environments.

Sato and Jenkins identified the boreholes called Karethraichnus; however, they were unable to match the characteristics of the boreholes they found with those made by any currently described species. This only meant one thing: that they had stumbled onto a completely new species! They have accordingly named this new species as Karethraichnus zaratan.

Sato is excited about the implications of their findings, stating, “This is the first study to report this unique behavior of boring bivalves as a symbiont of living marine vertebrate, which is a significant finding for the paleoecology and evolution of ancient boring bivalve clades.” Previously, no such species had been shown to live on the carapace of living vertebrates. Instead, they were often reported to occur on the remains of marine turtles and other vertebrates, laying on the ocean floor alongside various decomposing organisms. By attaching themselves on a live, free-swimming substrate, such as the carapace of a marine turtle, these pholadoid bivalves may have paved the way for a novel, yet-unknown evolutionary path of accessing previously unexplored niches and diversifying into new species. As the tracemaker bivalves of Karethraichnus zaratan are considered to belong to one of the basal groups for Pholadoidea, this knowledge is crucial for understanding the evolutionary history of extant organisms in this group.

Reference:
Robert G. Jenkins, Kei Sato. Mobile Home for Pholadoid Boring Bivalves: First Example from a Late Cretaceous Sea Turtle in Hokkaido Japan. PALAIOS, 2020; 35 (5): 228 DOI: 10.2110/palo.2019.077

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

From emus to woodpeckers, modern birds show remarkable diversity in skull shape and size, often hypothesized to be the result of a sudden hastening of evolution following the mass extinction that killed their non-avian dinosaur cousins at the end of the Cretaceous 66 million years ago. But this is not the case according to a study by Ryan Nicholas Felice at University College London, publishing August 18, 2020 in the open-access journal PLOS Biology. In the most detailed study yet of bird skull morphology, Felice and an international team of researchers show that the rate of evolution actually slowed in birds compared to non-avian dinosaurs.

The researchers used high-dimensional 3-D geometric morphometrics to map the shape of 354 living and 37 extinct avian and non-avian dinosaurs in unprecedented detail and performed phylogenetic analyses to test for a shift in the pace of evolution after the origin of birds. They found that all regions of the skull evolved more rapidly in non-avian dinosaurs than in birds, but certain regions showed rapid pulses of evolution in particular lineages.

For example, in non-avian dinosaurs, rapid evolutionary changes in the jaw joint were associated with changes in diet, while accelerated evolution of the roof of the skull occurred in lineages that sported bony ornaments such as horns or crests. In birds, the most rapidly evolving part of the skull was the beak, which the authors attribute to adaptation to different food sources and feeding strategies.

The authors say that overall slower pace of evolution in birds compared to non-avian dinosaurs calls into question a long-standing hypothesis that the diversity seen in modern birds resulted from rapid evolution as part of an adaptive radiation following the end-Cretaceous extinction event.

Reference:
Felice RN, Watanabe A, Cuff AR, Hanson M, Bhullar B-AS, Rayfield ER, et al. (2020) Decelerated dinosaur skull evolution with the origin of birds. PLoS Biol 18(8): e3000801. doi.org/10.1371/journal.pbio.3000801

Note: The above post is reprinted from materials provided by Public Library of Science.

Scientists studying leaves from a 23-million-year-old forest have for the first time linked high levels of atmospheric carbon dioxide with increased plant growth, and the hot climate off the time. The finding adds to the understanding of how rising CO2 heats the Earth, and how the dynamics of plant life could shift within decades, when CO2 levels may closely mirror those of the distant past.

Scientists retrieved the leaves from a unique onetime New Zealand lake bed that holds the remains of plants, algae, spiders, beetle, flies, fungi and other living things from a warm period known as the early Miocene. Scientists have long postulated that CO2 was high then, and some plants could harvest it more efficiently for photosynthesis. This is the first study to show that those things actually happened in tandem. The findings were published this week in the journal Climate of the Past.

“The amazing thing is that these leaves are basically mummified, so we have their original chemical compositions, and can see all their fine features under a microscope,” said lead author Tammo Reichgelt, an adjunct scientist at Columbia University’s Lamont-Doherty Earth Observatory and assistant professor of geosciences at the University of Connecticut. “Evidence has been building that CO2 was high then, but there have been paradoxes.”

The so-called “carbon fertilization effect” has vast implications. Lab and field experiments have shown that when CO2 levels rise, many plants increase their rate of photosynthesis, because they can more efficiently remove carbon from the air, and conserve water while doing so. Indeed, a 2016 study based on NASA satellite data shows a “global greening” effect mainly due to rising levels of human-made CO2 over recent decades; a quarter to a half of the planet’s vegetated lands have seen increases in leaf volume on trees and plants since about 1980. The effect is expected to continue as CO2 levels rise.

This might seem like good news, but the reality is more complex. Increased CO2 absorption will not come close to compensating for what humans are pouring into the air. Not all plants can take advantage, and among those who do, the results can vary depending on temperature and availability of water or nutrients. And, there is evidence that when some major crops photosynthesize more rapidly, they absorb relatively less calcium, iron, zinc and other minerals vital for human nutrition. Because much of today’s plant life evolved in a temperate, low-CO2 world, some natural and agricultural ecosystems could be upended by higher CO2 levels, along with the rising temperatures and shifts in precipitation they bring. “How it plays out is anyone’s guess,” said Reichgelt. “It’s another layer of stress for plants. It might be great for some, and horrible for others.”

The deposit is located in a small, long-extinct volcanic crater now located on a farm near the southern New Zealand city of Dunedin. The crater, about a kilometer across, once held an isolated lake where successive layers of sediments built up from the surrounding environment. The feature was recognized only within about the last 15 years; scientists dubbed it Foulden Maar. Recognizing it as a scientific gold mine, they have been studying it ever since. Some have also been fighting an actual mining company that wants to strip the deposit for livestock feed.

In the new study, the researchers took samples from a 2009 drill core that penetrated 100 meters to near the bottom of the now-dry lake bed. Larded in between whitish annual layers of silica-rich algae that bloomed each spring for 120,000 years are alternating blackish layers of organic matter that fell in during other seasons. These include countless leaves from a subtropical evergreen forest. They are preserved so perfectly that scientists can see microscopic veins and stomata, the pores by which leaves take in air and concurrently release water during photosynthesis. Unlike most fossils, the leaves also retain their original chemical compositions. It is the only such known deposit in the Southern Hemisphere, and far better preserved than the few similar ones known from the north.

The Miocene has long been a source of confusion for paleoclimate researchers. Average global temperatures are thought to have been 3 to 7 degrees C hotter than today, and ice largely disappeared at the poles. Yet many proxies, mainly derived from marine organisms, have suggested CO2 levels were only about 300 parts per million-similar to those of preindustrial human times, and not enough to account for such warming. With evidence of high CO2 elusive, scientists have speculated that previous proxy measurements must be off.

Based on the new study and a related previous one also at Foulden Maar, the researchers were able to get at this conundrum. They analyzed the carbon isotopes within leaves from a half-dozen tree species found at various levels in the deposit. This helped them zero in on the carbon content of the atmosphere at the time. They also analyzed the geometry of the leaves’ stomata and other anatomical features, and compared these with modern leaves. By combining all the data into a model, they found that atmospheric CO2 was not 300ppm, but about 450-a good match for the temperature data. Second, they showed that the trees were super-efficient at sucking in carbon through the stomata, without leaking much water through the same route-a factor that all plants must account for. This allowed them to grow in marginal areas that otherwise would have been too dry for forests. The researchers say this higher efficiency was very likely mirrored in forests across the northern temperate latitudes, with their far greater landmasses.

Human emissions have now pushed CO2 levels to about 415 parts per million, and they will almost certainly reach 450 by about 2040-identical to those experienced by the Foulden Maar forest. Estimates of the resulting temperature increases over decades and centuries vary, but the new study suggests that most are in the ballpark.

“It all fits together, it all makes sense,” said study coauthor William D’Andrea, a paleoclimate scientist at Lamont-Doherty. In addition to showing how plants might react directly to CO2, “this should give us more confidence about how temperatures will change with CO2 levels,” he said.

Study coauthor Daphne Lee, a paleontologist at New Zealand’s University of Otago, led the charge to study Foulden Maar’s rich ecosystem after it came to light. More recently, she became an unexpected defender of the maar, when a company with owners in Malaysia and the United Kingdom announced plans to strip-mine the deposit for use as a feed additive for for pigs, ducks and other intensively farmed animals. With many more discoveries probably to be made, scientists were horrified, and allied themselves with locals who feared noise and dust. The Dunedin city council is now looking into buying the land to protect it.

The study was also coauthored by Ailín del Valdivia-McCarthy, a former intern at Lamont-Doherty; Bethany Fox of the University of Huddersfield; Jennifer Bannister of the University of Otago; John Conran of the University of Adelaide; and William Lee of the University of Auckland.

Reference:
Tammo Reichgelt, William J. D’Andrea, Ailín del C. Valdivia-McCarthy, Bethany R. S. Fox, Jennifer M. Bannister, John G. Conran, William G. Lee, Daphne E. Lee. Elevated CO2, increased leaf-level productivity, and water-use efficiency during the early Miocene. Climate of the Past, 2020; 16 (4): 1509 DOI: 10.5194/cp-16-1509-2020

Note: The above post is reprinted from materials provided by Earth Institute at Columbia University. Original written by Kevin Krajick.