First complete dinosaur skeleton ever found is ready for its closeup at last

The first complete dinosaur skeleton ever identified has finally been studied in detail and found its place in the dinosaur family tree, completing a project that began more than a century and a half ago.

The skeleton of this dinosaur, called Scelidosaurus, was collected more than 160 years ago on west Dorset’s Jurassic Coast. The rocks in which it was fossilised are around 193 million years old, close to the dawn of the Age of Dinosaurs.

This remarkable specimen — the first complete dinosaur skeleton ever recovered — was sent to Richard Owen at the British Museum, the man who invented the word dinosaur.

So, what did Owen do with this find? He published two short papers on its anatomy, but many details were left unrecorded. Owen did not reconstruct the animal as it might have appeared in life and made no attempt to understand its relationship to other known dinosaurs of the time. In short, he ‘re-buried’ it in the literature of the time, and so it has remained ever since: known, yet obscure and misunderstood.

Over the past three years, Dr David Norman from Cambridge’s Department of Earth Sciences has been working to finish the work which Owen started, preparing a detailed description and biological analysis of the skeleton of Scelidosaurus, the original of which is stored at the Natural History Museum in London, with other specimens at Bristol City Museum and the Sedgwick Museum, Cambridge.

The results of Norman’s work, published as four separate studies in the Zoological Journal of the Linnean Society of London, not only reconstruct what Scelidosaurus looked like in life, but reveal that it was an early ancestor of ankylosaurs, the armour-plated ‘tanks’ of the Late Cretaceous Period.

For more than a century, dinosaurs were primarily classified according to the shape of their hip bones: they were either saurischians (‘lizard-hipped’) or ornithischians (‘bird-hipped’).

However, in 2017, Norman and his former PhD students Matthew Baron and Paul Barrett argued that these dinosaur family groupings needed to be rearranged, re-defined and re-named. In a study published in Nature, the researchers suggested that bird-hipped dinosaurs and lizard-hipped dinosaurs such as Tyrannosaurus evolved from a common ancestor, potentially overturning more than a century of theory about the evolutionary history of dinosaurs.

Another fact that emerged from their work on dinosaur relationships was that the earliest known ornithischians first appeared in the Early Jurassic Period. “Scelidosaurus is just such a dinosaur and represents a species that appeared at, or close to, the evolutionary ‘birth’ of the Ornithischia,” said Norman, who is a Fellow of Christ’s College, Cambridge. “Given that context, what was actually known of Scelidosaurus? The answer is remarkably little!”

Norman has now completed a study of all known material attributable to Scelidosaurus and his research has revealed many firsts.

“Nobody knew that the skull had horns on its back edge,” said Norman. “It had several bones that have never been recognised in any other dinosaur. It’s also clear from the rough texturing of the skull bones that it was, in life, covered by hardened horny scutes, a little bit like the scutes on the surface of the skulls of living turtles. In fact, its entire body was protected by skin that anchored an array of stud-like bony spikes and plates.”

Now that its anatomy is understood, it is possible to examine where Scelidosaurus sits in the dinosaur family tree. It had been regarded for many decades as an early member of the group that included the stegosaurs, including Stegosaurus with its huge bony plates along its spine and a spiky tail, and ankylosaurs, the armour-plated ‘tanks’ of the dinosaur era, but that was based on a poor understanding of the anatomy of Scelidosaurus. Now it seems that Scelidosaurus is an ancestor of the ankylosaurs alone.

“It is unfortunate that such an important dinosaur, discovered at such a critical time in the early study of dinosaurs, was never properly described,” said Norman. “It has now — at last! — been described in detail and provides many new and unexpected insights concerning the biology of early dinosaurs and their underlying relationships. It seems a shame that the work was not done earlier but, as they say, better late than never.”


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Materials provided by University of Cambridge. Original written by Sarah Collins. Note: Content may be edited for style and length.

Early Cambrian fossil: Bizarre half-billion-year-old worm with tentacles solves evolutionary mystery

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.


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Fossils reveal diversity of animal life roaming Europe 2 million years ago

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.


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Materials provided by University of Arkansas. Original written by Matt McGowan. Note: Content may be edited for style and length.

Cliff collapse reveals 313-million-year-old fossil footprints in Grand Canyon National Park

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.advertisementhttps://www.swoop-assets.com/Epclusa_NPI/Q3/Treater2_Treater_300x250/index.html

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.


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New species of dinosaur discovered on Isle of Wight

A new study by Palaeontologists at the University of Southampton suggests four bones recently found on the Isle of Wight belong to new species of theropod dinosaur, the group that includes Tyrannosaurus rex and modern-day birds.

The dinosaur lived in the Cretaceous period 115 million years ago and is estimated to have been up to four metres long.

The bones were discovered on the foreshore at Shanklin last year and are from the neck, back and tail of the new dinosaur, which has been named Vectaerovenator inopinatus.

The name refers to the large air spaces in some of the bones, one of the traits that helped the scientists identify its theropod origins. These air sacs, also seen in modern birds, were extensions of the lung, and it is likely they helped fuel an efficient breathing system while also making the skeleton lighter.

The fossils were found over a period of weeks in 2019 in three separate discoveries, two by individuals and one by a family group, who all handed in their finds to the nearby Dinosaur Isle Museum at Sandown.

The scientific study has confirmed the fossils are very likely to be from the same individual dinosaur, with the exact location and timing of the finds adding to this belief.

Robin Ward, a regular fossil hunter from Stratford-upon-Avon, was with his family visiting the Isle of Wight when they made their discovery. He said: “The joy of finding the bones we discovered was absolutely fantastic. I thought they were special and so took them along when we visited Dinosaur Isle Museum. They immediately knew these were something rare and asked if we could donate them to the museum to be fully researched.”

James Lockyer, from Spalding, Lincolnshire was also visiting the Island when he found another of the bones. Also a regular fossil hunter, he said: “It looked different from marine reptile vertebrae I have come across in the past. I was searching a spot at Shanklin and had been told and read that I wouldn’t find much there. However, I always make sure I search the areas others do not, and on this occasion it paid off.”

Paul Farrell, from Ryde, Isle of Wight, added: “I was walking along the beach, kicking stones and came across what looked like a bone from a dinosaur. I was really shocked to find out it could be a new species.”

After studying the four vertebrae, paleontologists from the University of Southampton confirmed that the bones are likely to belong to a genus of dinosaur previously unknown to science. Their findings will be published in the journal Papers in Palaeontology, in a paper co-authored by those who discovered the fossils.advertisementhttps://www.swoop-assets.com/Epclusa_NPI/Q3/Treater2_Treater_300x250/index.html

Chris Barker, a PhD student at the university who led the study, said: “We were struck by just how hollow this animal was — it’s riddled with air spaces. Parts of its skeleton must have been rather delicate.

“The record of theropod dinosaurs from the ‘mid’ Cretaceous period in Europe isn’t that great, so it’s been really exciting to be able to increase our understanding of the diversity of dinosaur species from this time.

“You don’t usually find dinosaurs in the deposits at Shanklin as they were laid down in a marine habitat. You’re much more likely to find fossil oysters or drift wood, so this is a rare find indeed.”

It is likely that the Vectaerovenator lived in an area just north of where its remains were found, with the carcass having washed out into the shallow sea nearby.

Chris Barker added: “Although we have enough material to be able to determine the general type of dinosaur, we’d ideally like to find more to refine our analysis. We are very grateful for the donation of these fossils to science and for the important role that citizen science can play in palaeontology.”

The Isle of Wight is renowned as one of the top locations for dinosaur remains in Europe, and the new Vectaerovenator fossils will now go on display at the Dinosaur Isle Museum at Sandown, which houses an internationally important collection.

Museum curator, Dr Martin Munt, said: “This remarkable discovery of connected fossils by three different individuals and groups will add to the extensive collection we have and it’s great we can now confirm their significance and put them on display for the public to marvel at.

“We continue to undertake public field trips from the museum and would encourage anyone who finds unusual fossils to bring them in so we can take a closer look. However, fossil hunters should remember to stick to the foreshore, and avoid going near the cliffs which are among the most unstable on the Island.”

Isle of Wight Council Cabinet member for environment and heritage, Councillor John Hobart, said: “This is yet another terrific fossil find on the Island which sheds light on our prehistoric past — all the more so that it is an entirely new species. It will add to the many amazing items on display at the museum.”


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Study sheds light on the evolution of the earliest dinosaurs

The classic dinosaur family tree has two subdivisions of early dinosaurs at its base: the Ornithischians, or bird-hipped dinosaurs, which include the later Triceratops and Stegosaurus; and the Saurischians, or lizard-hipped dinosaurs, such as Brontosaurus and Tyrannosaurus.

In 2017, however, this classical view of dinosaur evolution was thrown into question with evidence that perhaps the lizard-hipped dinosaurs evolved first — a finding that dramatically rearranged the first major branches of the dinosaur family tree.

Now an MIT geochronologist, along with paleontologists from Argentina and Brazil, has found evidence to support the classical view of dinosaur evolution. The team’s findings are published today in the journal Scientific Reports.

The team reanalyzed fossils of Pisanosaurus, a small bipedal dinosaur that is thought to be the earliest preserved Ornithiscian in the fossil record. The researchers determined that the bird-hipped herbivore dates back to 229 million years ago, which is also around the time that the earliest lizard-hipped Saurischians are thought to have appeared.advertisement

The new timing suggests that Ornithiscians and Saurischians first appeared and diverged from a common ancestor at roughly the same time, giving support to the classical view of dinosaur evolution.

The researchers also dated rocks from the Ischigualasto Formation, a layered sedimentary rock unit in Argentina that is known for having preserved an abundance of fossils of the very earliest dinosaurs. Based on these fossils and others across South America, scientists believe that dinosaurs first appeared in the southern continent, which at the time was fused together with the supercontinent of Pangaea. The early dinosaurs are then thought to have diverged and fanned out across the world.

However, in the new study, the researchers determined that the period over which the Ischigualasto Formation was deposited overlaps with the timing of another important geological deposit in North America, known as the Chinle Formation.

The middle layers of the Chinle Formation in the southwestern U.S. contain fossils of various fauna, including dinosaurs that appear to be more evolved than the earliest dinosaurs. The bottom layers of this formation, however, lack animal fossil evidence of any kind, let alone early dinosaurs. This suggests that conditions within this geological window prevented the preservation of any form of life, including early dinosaurs, if they walked this particular region of the world.

“If the Chinle and Ischigualasto formations overlap in time, then early dinosaurs may not have first evolved in South America, but may have also been roaming North America around the same time,” says Jahandar Ramezani, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, who co-authored the study. “Those northern cousins just may not have been preserved.”

The other researchers on the study are first author Julia Desojo from the National University of La Plata Museum, and a team of paleontologists from institutions across Argentina and Brazil.

“Following footsteps”

The earliest dinosaur fossils found in the Ischigualasto Formation are concentrated within what is now a protected provincial park known as “Valley of the Moon” in the San Juan Province. The geological formation also extends beyond the park, albeit with fewer fossils of early dinosaurs. Ramezani and his colleagues instead looked to study one of the accessible outcrops of the same rocks, outside of the park.

They focused on Hoyada del Cerro Las Lajas, a less-studied outcrop of the Ischigualasto Formation, in La Rioja Province, which another team of paleontologists explored in the 1960s.

“Our group got our hands on some of the field notes and excavated fossils from those early paleontologists, and thought we should follow their footsteps to see what we could learn,” Desojo says.

Over four expeditions between 2013 to 2019, the team collected fossils and rocks from various layers of the Las Lajas outcrop, including more than 100 new fossil specimens, though none of these fossils were of dinosaurs. Nevertheless, they analyzed the fossils and found they were comparable, in both species and relative age, to nondinosaur fossils found in the park region of the same Ischigualasto Formation. They also found out that the Ischigualasto Formation in Las Lajas was significantly thicker and much more complete than the outcrops in the park. This gave them confidence that the geological layers in both locations were deposited during the same critical time interval.

Ramezani then analyzed samples of volcanic ash collected from several layers of the Las Lajas outcrops. Volcanic ash contains zircon, a mineral that he separated from the rest of the sediment, and measured for isotopes of uranium and lead, the ratios of which yield the mineral’s age.

With this high-precision technique, Ramezani dated samples from the top and bottom of the outcrop, and found that the sedimentary layers, and any fossils preserved within them, were deposited between 230 million and 221 million years ago. Since the team determined that the layered rocks in Las Lajas and the park match in both species and relative timing, they could also now determine the exact age of the park’s more fossil-rich outcrops.

Moreover, this window overlaps significantly with the time interval over which sediments were deposited, thousands of kilometers northward, in the Chinle Formation.

“For many years, people thought Chinle and Ischigualasto formations didn’t overlap, and based on that assumption, they developed a model of diachronous evolution, meaning the earliest dinosaurs appeared in South America first, then spread out to other parts of the world including North America,” Ramezani says. “We’ve now studied both formations extensively, and shown that diachronous evolution isn’t really based on sound geology.”

A family tree, preserved

Decades before Ramezani and his colleagues set out for Las Lajas, other paleontologists had explored the region and unearthed numerous fossils, including remains of Pisanosaurus mertii, a small, light-framed, ground-dwelling herbivore. The fossils are now preserved in an Argentinian museum, and scientists have gone back and forth on whether it is a true dinosaur belonging to the Ornithiscian group, or a ” basal dinosauromorph” — a kind of pre-dinosaur, with features that are almost, but not quite fully, dinosaurian.

“The dinosaurs we see in the Jurassic and Cretaceous are highly evolved, and ones we can nicely identify, but in the late Triassic, they all looked very much alike, so it’s very hard to distinguish them from each other, and from basal dinosauromorphs,” Ramezani explains.

His collaborator Max Langer from the University of São Paulo in Brazil painstakingly reanalyzed the museum-preserved fossil of Pisanosaurus, and concluded, based on certain key anatomical features, that it is indeed a dinosaur — and what’s more, that it is the earliest preserved Ornithiscian specimen. Based on Ramezani’s dating of the outcrop and the interpretation of Pisanosaurus, the researchers concluded that the earliest bird-hipped dinosaurs appeared around 229 million years ago — around the same time as their lizard-hipped counterparts.

“We can now say the earliest Ornithiscians first showed up in the fossil record roughly around the same time as the Saurischians, so we shouldn’t throw away the conventional family tree,” Ramezani says. “There are all these debates about where dinosaurs appeared, how they diversified, what the family tree looked like. A lot of those questions are tied to geochronology, so we need really good, robust age constraints to help answer these questions.”

This research was mainly funded by the National Council for Scientific and Technical Research (Argentina) and the São Paulo State Research Support Foundation (Brazil). Geochronologic research at the MIT Isotope Lab has been supported in part by the U.S. National Science Foundation.


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What happens in Vegas, may come from the Arctic?

A cave deep in the wilderness of central Nevada is a repository of evidence supporting the urgent need for the Southwestern U.S. to adopt targets aimed at reducing greenhouse gas emissions, a new UNLV study finds.

UNLV climate scientist Matthew Lachniet and colleagues have compiled a detailed, 13,000-year climate history from stalagmite specimens in Leviathan Cave, located in the southern Great Basin, which provides clues for the mitigation of climate change today.

These ancient climate records show that Nevada was even hotter and drier in the past than it is today, and that one 4,000-year period in particular may represent a true, “worst-case” scenario picture for the Southwest and the Colorado River Basin — and the millions of people who rely on its water supply.

At that time, the long-term hot and dry climate of the region was linked to warm Arctic seas and a lack of sea ice, as well as warming in the western tropical Pacific Ocean, the cave record shows.

This parallels today and the near future, as the release of human carbon emissions into the atmosphere will warm the Arctic and possibly the western tropical Pacific, and is expected to result in long-term arid conditions for Nevada and the broader Colorado River Basin.

If the arid conditions become permanent, then the water supply in the Colorado River Basin is expected to decrease, which researchers say would imperil critical water resources for millions of people who live in the Southwest U.S.

“The last few decades have seen increasingly severe ‘hot droughts’ in the Colorado River Basin, when high temperatures coincide with less rainfall, and which have startled climate scientists and water policy managers,” Lachniet said. “But these dry intervals don’t usually last more than a few decades. In contrast, our new data show that Nevada climate can experience an extended interval of aridity for thousands of years, not just a few decades.”

The recent Southwestern U.S. drought that began in 2001, which has resulted in historic low reservoir levels in Lake Mead, is one indicator of the gravity of the problem. The Colorado River and Rio Grande basins are critical human support systems as their headwaters in the Rocky Mountains supply snow-fed water for myriad economic uses and support 56 million residents throughout the region.

“‘Business as usual’ scenarios for anthropogenic warming carry the risk of tipping the Southwest into an extended state of aridification,” researchers wrote.

The paper, published in the journal Paleoceanography and Paleoclimatology, provides a clearer and more comprehensive picture of the Southwest’s climate history compared to tree ring records which extend only 2,000 years into the past.

Stalagmites — like those located in Leviathan Cave — are common cave formations that act as ancient rain gauges to record historic climate data. Stalagmites grow upward at rates of inches every few hundred years as mineral-rich waters seep through the ground above and drop from the tips of stalactites on cave ceilings.

These deposits more accurately represent a long-term shift toward a more arid climate as they hold data that extends deeper into the past.

A former analysis of one tree ring record, for example, pointed to a 10-year drought in the Medieval era as being a “worst case” predictor of a future, comparable drought, as compared to the more persistent and sustained 4,000-year period of aridity presented in Lachniet’s new study.

Regionally, paleoclimate records from other sources like lakes, landforms, pollen, and others, also support the conclusion of warmth and aridity during the same 4,000-year period.

Researchers also found that the Leviathan Cave region, where the stalagmite specimen was collected, is representative of climate conditions in most of the Mojave Desert and the southern Great Basin, and that the data has implications for the broader desert region.

Lachniet and colleagues say that their study can be a resource for policymakers today in adopting measures to reduce greenhouse gas emissions which will in turn “minimize oceanic and Arctic warming.”

“There already is evidence that droughts in the Southwest are partly caused by humans because of the higher temperatures and more evaporation in surface waters like Lake Mead,” Lachniet said. “The new fossil-fuel climate might end up making these droughts permanent.”


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Materials provided by University of Nevada, Las Vegas. Original written by Natalie Bruzda. Note: Content may be edited for style and length.

Growth rate of common trilobites

If you’ve ever held a trilobite fossil, seen one in a classroom, or walked by one in a store, chances are it was Elrathia kingii, one of the most common and well-recognized trilobites, and collected by the hundreds of thousands in western Utah. But despite the popularity of this species, scientists had not determined how it grew — from hatchling to juvenile to adult — until now. New work from the American Museum of Natural History published today in the journal Papers in Palaeontology describes the development and growth rate of Elrathia kingii — only the second such dataset to be compiled for a trilobite — allowing for the first comparison among trilobite species.

“There’s quite a big size range among trilobites. Some never got bigger than about a centimeter, while the largest on record is 72 centimeters (28 inches),” said Melanie Hopkins, an associate curator in the Museum’s Division of Paleontology and the study’s author. “Growth-rate studies like this one can help us tackle some of the big-picture questions: How did some trilobites get so big? What was the environmental context for that? And how did body size evolve over the evolutionary history of the clade?”

Trilobites are a group of extinct marine arthropods — distantly related to the horseshoe crab — that lived for almost 300 million years. They were incredibly diverse, with more than 20,000 described species. Their fossilized exoskeletons are preserved in sites all over the world, from the United States to China. Like insects, they molted throughout their lifetimes, leaving clues to how they changed during development. But to calculate the species’ growth rate, scientists need fossils representing all stages of the animal’s life — and lots of them.advertisement

“There are tons of specimens of Elrathia kingii out there but most of them are adults, and data from exactly where they were collected is inconsistent,” Hopkins said. “I needed material that I could collect from as small a section as possible that included a lot of juveniles.”

So in May 2018, Hopkins spent five days in Utah with a crew consisting of Museum staff and volunteers at a new fossil site said to preserve bucketloads of Elrathia kingii. By the end of the trip, they had collected about 500 specimens — many of them juveniles, which can be as small as half a millimeter long — from a section of outcrop just 1.5 meters (about 5 feet) long.

Hopkins estimated the growth rate and compared it to previously published data on a different trilobite, Aulacopleura konincki — the first time two trilobite species have been compared in this way. The two species look very similar and Hopkins found that they also grow in similar ways: for example, the growth of the trunk — the area immediately below the trilobite’s head made up of segments that increase with age — was controlled by a growth gradient, with those that were younger and closer to the back of the body undergoing faster growth. But while Elrathia kingii was smaller in early development and went through fewer molts before adulthood, it had faster growth rates, ultimately reaching sizes on par with Aulacopleura konincki, the largest of which are about 4 centimeters long.

In future studies, Hopkins is planning to add growth-rate data on different, more diverse-looking trilobite species to her models.


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Fossil jawbone from Alaska is a rare case of a juvenile Arctic dromaeosaurid dinosaur

A small piece of fossil jawbone from Alaska represents a rare example of juvenile dromaeosaurid dinosaur remains from the Arctic, according to a study published July 8, 2020 in the open-access journal PLOS ONE by Alfio Alessandro Chiarenza of the Imperial College London, UK, and co-authors Anthony R. Fiorillo, Ronald S. Tykoski, Paul J. McCarthy, Peter P. Flaig, and Dori L. Contreras.

Dromaeosaurids are a group of predatory dinosaurs closely related to birds, whose members include well-known species such as Deinonychus and Velociraptor. These dinosaurs lived all over the world, but their bones are often small and delicate and rarely preserve well in the fossil record, complicating efforts to understand the paths they took as they dispersed between continents.

The Prince Creek Formation of northern Alaska preserves the largest collection of polar dinosaur fossils in the world, dating to about 70 million years ago, but the only dromaeosaurid remains found so far have been isolated teeth. The jaw fossil described in this study is a mere 14mm long and preserves only the tip of the lower jaw, but it is the first known non-dental dromaeosaurid fossil from the Arctic. Statistical analysis indicates this bone belongs to a close relative of the North American Saurornitholestes.

North American dromaeosaurids are thought to trace their origins to Asia, and Alaska would have been a key region for the dispersal of their ancestors. This new fossil is a tantalizing clue toward understanding what kinds of dromaeosaurs inhabited this crucial region. Furthermore, the early developmental stage of the bone suggests this individual was still young and was likely born nearby; in contrast to previous suggestions that this part of Alaska was exclusively a migratory pathway for many dinosaurs, this is strong evidence that some dinosaurs were nesting here. The authors suggest that future findings may allow a more complete understanding of these mysterious Arctic dromaeosaurids.

Chiarenza summarizes: “There are places where dinosaur fossils are so common that a scrap of bone, in most cases, cannot really add anything scientifically informative anymore: this is not the case with this Alaskan specimen. Even with such an incomplete jaw fragment, our team was not only able to work out the evolutionary relationships of this dinosaur, but also to picture something more on the biology of these animals, ultimately gaining more information on this Ancient Arctic ecosystem.” Fiorillo adds: “Years ago when dinosaurs were first found in the far north, the idea challenged what we think we know about dinosaurs. For some time afterwards, there was a great debate as to whether or not those Arctic dinosaurs migrated or lived in the north year round. All of those arguments were somewhat speculative in nature. This study of a predatory dinosaur jaw from a baby provides the first physical proof that at least some dinosaurs not only lived in the far north, but they thrived there. One might even say, our study shows that the ancient north was a great place to raise a family and now we have to figure out why.”


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Different tracks, same dinosaurs: Researchers dig deeper into dinosaur movements

When picturing dinosaur tracks, most people imagine a perfectly preserved mold of a foot on firm layer of earth. But what if that dinosaur was running through mud, sinking several inches — or even up to their ankles — into the ground as it moved?

Using sophisticated X-ray-based technology, a team of Brown University researchers tracked the movements of guineafowl to investigate how their feet move below ground through various substrates and what those findings could mean for understanding fossil records left behind by dinosaurs.

They found that regardless of the variability in substrates, or the guineafowl moving at different speeds, sinking at different depths or engaging in different behaviors, the birds’ overall foot movement remained the same: The toes spread as they stepped onto the substrate surface, remained spread as the foot sank, collapsed and drew back as they were lifted from the substrate, and exited the substrate in front of the point of entry, creating a looping pattern as they walked.

And part of what that means is that fossilized dinosaur tracks that look distinct from each other, and appear to be from different species, might instead come from the same dinosaurs.

“This is the first study that’s really shown how the bird foot is moving below ground, showing the patterns of this subsurface foot motion and allowing us to break down the patterns that we’re seeing in a living animal that has feet similar to those of a dinosaur,” said Morgan Turner, a Ph.D. candidate at Brown in ecology and evolutionary biology and lead author of the research. “Below ground, or even above ground, they’re responding to these soft substrates in a very similar way, which has potentially important implications for our ability to study the movement of these animals that we can’t observe directly anymore.”

The findings were published on Wednesday, July 1, in the Royal Society journal Biology Letters.

To make the observations, Turner and her colleagues, Professor of Biology and Medical Science Stephen Gatesy and Peter Falkingham, now at Liverpool John Moores University, used a 3D-imaging technology developed at Brown called X-ray Reconstruction of Moving Morphology (XROMM). The technology combines CT scans of a skeleton with high-speed X-ray video, aided by tiny implanted metal markers, to create visualizations of how bones and muscles move inside humans and animals. In the study, the team used XROMM to watch guineafowl move through substrates of different hydration and compactness, analyzing how their feet moved underground and the tracks left behind.

Sand, typically a dense combination of quartz and silica, does not lend itself well to X-ray imaging, so the team used poppy seeds to emulate sand. Muds were made using small glass bubbles, adding various amount of clay and water across 107 trials to achieve different consistencies and realistic tracks.

They added metal markers underneath the claws of the guineafowl to allow for tracking in 3D space. It’s these claw tips that the researchers think are least disturbed by mud flow and other variables that can impact and distort the form of the track.

Despite the variation, the researchers observed a consistent looping pattern.

“The loops by themselves I don’t think are that interesting,” Gatesy said. “People are like, ‘That’s nice. Birds do this underground. So what?’ It was only when [Turner] went back into it and said, ‘What if we slice those motion trails at different depths as if they were footprints?’ Then we made the nice connection to the fossils.”

By “slicing” through the 3D images of the movement patterns at different depths, the researchers found similarities between the guineafowl tracks and fossilized dinosaur tracks.

“We don’t know what these dinosaurs were doing, we don’t know what they were walking through exactly, we don’t know how big they were or how deep they were sinking, but we can make this really strong connection between how they were moving and some level of context for where this track is being sampled from within that movement,” Turner said.

By recognizing the movement patterns, as well as the entry and exit point of the foot through various substrates, the team says they’re able to gain a better understanding of what a dinosaur track could look like.

“You end up generating this big diversity of track shapes from a very simple foot shape because you’re sampling at different depths and it’s moving in complicated ways,” Gatesy said. “Do we really have 40 different kinds of creatures, each with a differently shaped foot, or are we looking at some more complicated interaction that leaves behind these remnants that are partly anatomical and partly motion and partly depth?”

To further their research, the team spent time at the Beneski Museum of Natural History at Amherst College in Massachusetts, which is home to an expansive collection of penetrative tracks discovered in the 1800s by geologist Edward Hitchcock.

Hitchcock originally believed that his collection housed fossil tracks from over 100 distinct animals. Because of the team’s work with XROMM, Gatesy now thinks it’s possible that at least half of those tracks are actually from the same dinosaurs, just moving their feet in slightly different ways or sampled at slightly different depths.

“Going to museum together and being able to pick out these features and say, ‘We think this track is low in the loop and we think this one is high,’ that was the biggest moment of insight for me,” Turner said.

Turner says she hopes their research can lead to a greater interest in penetrative tracks, even if they seem a little less pretty or polished than the tracks people are used to seeing in museums.

“They have so much information in them,” Turner said, “and I hope that this gives people a lens, a new way to view these footprints and appreciate the movement preserved within in them.”

This work was supported by the US National Science Foundation (EAR 1452119 to SMG and PLF; IOS 0925077 to SMG), a Marie Curie International Outgoing Fellowship within the 7th European Framework Programme to PLF, and the Bushnell Research and Education Fund to MLT.


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