Scientists have discovered an extraordinary collection of fossils that reveal in detail how life recovered after a catastrophic event: the asteroid impact that wiped out the dinosaurs 66 million years ago at the end of the Cretaceous Period. Described in a published Oct. 24 in the journal Science, the unprecedented find — thousands of exceptionally preserved animal and plant fossils from the first million years after the catastrophe — shines light on how life emerged from one of Earth’s darkest hours.

Scientists unearthed this new record from the first million years after the asteroid impact in the region around Colorado Springs, Colorado, which forms part of a larger geological province known as the . The find includes both plants and animals, painting a portrait of the emergence of the post-dinosaur world.

The team behind this discovery was led by two scientists at the Denver Museum of Nature & Science, lead author , the curator of vertebrate paleontology, and co-author , curator of paleobotany and director of Earth and space sciences. Among the co-authors is , a professor of biology at the 91̽�� and curator of vertebrate paleontology at the , who joined the team as an expert on the end-Cretaceous mass extinction and the evolution of mammals in its aftermath.

“I’ve been working on this time period and on these mammals for 21 years, and this is truly an exceptional window into this pivotal event in life history,” said Wilson, who was a curator at the Denver Museum of Nature & Science before joining the 91̽��faculty in 2007. “We change over from terrestrial ecosystems dominated by dinosaurs to those that become dominated by mammals in a geological blink of an eye.”

“The course of life on Earth changed radically on a single day 66 million years ago,” said Lyson. “Blasting our planet, an asteroid triggered the extinction of three of every four kinds of living organisms. While it was a really bad time for life on Earth, some things survived, including some of our earliest, earliest ancestors.”

A moment of serendipity pointed the way to these rare fossil finds. Lyson, who had been looking for post-impact vertebrate fossils without success, took inspiration from a fossil that had been sitting in a museum drawer and fossil-hunting techniques used by colleagues in South Africa. In the summer of 2016, he stopped looking for glinting bits of bone in the Denver Basin and instead zeroed in on egg-shaped rocks called concretions.

Cracking open the concretions, Lyson and Miller found fossils such as the skulls of mammals from the early generations of survivors of the mass extinction. Since most of what is understood from this era is based on tiny fragments of fossils, such as pieces of mammal teeth, finding a single skull would be exceptional. Lyson and Miller found four in a single day and more than a dozen in a week. So far, they’ve found fossils from at least 16 different mammalian species.

Wilson participated in excavations at Corral Bluffs, a site just east of Colorado Springs. He and co-author , an assistant professor at the City University of New York’s Brooklyn College, worked to identify the mammal fossil that the team found, calculate changes in body size over time and analyze the diversity of species after the asteroid impact. The researchers determined that just 100,000 years after the cataclysm, mammalian diversity had approximately doubled. At 300,000 years after the impact, the maximum body mass of mammals had increased threefold, and mammals were evolving specialized diets, possibly in response to changes in plant diversity.

These findings illustrate how the Denver Basin site also is adding evidence to the idea that the recovery and evolution of plants and animals were intricately linked after the asteroid impact. More than 6,000 leaf fossils were collected as part of the study to help determine how and when Earth’s forest rebounded after the mass extinction event. Combining a remarkable fossil plant record with the discovery of the fossil mammals allowed the team to link millennia-long warming spells to specific global events, including massive amounts of volcanism on the Indian subcontinent.

These events may have shaped the ecosystems half a world away. For example, the research team saw another increase in body size among mammals at about 700,000 years post-impact, which coincided with the evolution of legumes, then a new type of plant. Additional analyses of these fossils, as well as the unearthing of new specimens, will only deepen scientists’ understanding of this critical period in Earth’s history and the evolution of mammals that came before humans.

“Our understanding of the asteroid’s aftermath has been spotty,” Lyson explained. “These fossils tell us for the first time how exactly our planet recovered from this global cataclysm.”

Additional co-authors include David Krause, James Hagadorn, Antoine Bercovici, Farley Fleming, Ken Weissenburger with the Denver Museum of Nature & Science; William Clyde and Anthony Fuentes with the University of New Hampshire; Kirk Johnson and Rich Barclay with the Smithsonian Institution’s National Museum of Natural History; Matthew Butrim at Wesleyan University; Gussie Maccracken at the University of Maryland; and Ben Lloyd of Colorado College. The research was funded by the Lisa Levin Appel Family Foundation, M. Cleworth, Lyda Hill Philanthropies, David B. Jones Foundation, M.L. and S.R. Kneller, T. and K. Ryan, and J.R. Tucker as part of the Denver Museum of Nature & Science No Walls: Schools initiative.

For more information, contact Wilson at gpwilson@uw.edu.

Adapted from a release by the Denver Museum of Nature & Science.

The myth’s focus isn’t on dinosaurs. Its main characters are ancient mammals and their relatives, which together are known as . According to the myth, a world crowded with dinosaurs left little room for mammaliaforms. As a result, mammals and their kin remained tiny, mouse-like and primitive. The myth posits that mammals didn’t evolve diverse shapes, diets, behaviors and ecological roles until the 66 million years ago killed off the dinosaurs and “freed up” space for mammals.

“This is a very old idea, which makes it very hard to defeat,” said , a postdoctoral researcher in the Department of Biology at the 91̽��. “But this view of mammaliaforms simply doesn’t stand up to what we and others have found recently in the fossil record.”

Grossnickle is the lead and corresponding author of a published June 19 in that summarizes the latest fossil evidence for an alternative view: Mammals and their relatives have actually undergone three significant “ecological radiations” in their history. In evolutionary biology, a radiation occurs when a particular lineage invades and adapts to new ecological niches. In each of the radiations discussed in the review, mammaliaforms diversified from insect-chomping, rodent-like ancestors and adapted to a variety of ecological niches. New species arose that, for example, could climb, glide or burrow — and ate more specialized diets of meat, leaves or shellfish.

Two of these three ecological radiations of mammailaforms occurred during the Jurassic and Cretaceous periods when dinosaurs were thriving, according to Grossnickle and co-authors of in Chicago and , a 91̽��associate professor of biology and curator of vertebrate paleontology at the UW’s .

The co-authors summarize the three ecological radiations, each of which involved different groups of mammaliaforms:

• The oldest mammaliaform ecological radiation ran from 190 to 163 million years ago in the early-to-mid Jurassic Period — amid the breakup of the supercontinent Pangaea — and involved the first true mammals and their closest relatives.
• A second ecological radiation of mammals began 90 million years ago in the Late Cretaceous Period, shortly after flowering plants evolved, and ended at the 66 million years ago.
• The Paleocene-Eocene radiation began 66 million years ago around the time of the K-Pg event and ended about 34 million years ago, and led to the establishment of all the major lineages of placental and marsupial mammals alive today.

Each ecological radiation from more primitive, insect-eating, rodent-like ancestors. Many of the diverse forms that arose during the Jurassic and Cretaceous resemble species alive today, such as badgers, flying squirrels and even anteaters. But these dinosaur-era mammaliaforms are not the direct ancestors of their modern counterparts.

“These same ecological adaptations — for gliding, climbing, eating diverse diets — have evolved repeatedly in the history of mammals and their close relatives,” said Grossnickle.

Mammaliaforms that arose during the Jurassic radiation included the semi-aquatic, beaver-like ; , which likely resembled today’s flying squirrels; and the tree-climbing . These lineages died out by the mid-Cretaceous Period — for early mammals and their relatives, likely due to climate change and the relatively rapid turnover of whole ecosystems.

The Late Cretaceous ecological radiation followed this period of decline, and saw the rise of new forms of mammals. These included the badger-sized , a marsupial relative with the strongest pound-for-pound bite force of any known mammal, as well as , a herbivore with some skull features similar to sloths. These diverse groups of mammals perished alongside dinosaurs in the K-Pg mass extinction.

“The presence of this diversity of mammaliaforms in the Jurassic and Cretaceous overturns a classical interpretation of how mammals evolved,” said Wilson. “This new interpretation was really made possible by new fossil discoveries over the past two decades in places like China and Madagascar.”

The Paleocene-Eocene radiation of mammals, which began around the time of the K-Pg event, generated the ancestors of today’s marsupial and placental mammals – from kangaroos and zebras to blue whales and humans. This radiation’s strong connection to today’s mammals may explain how the myth arose that mammals remained static and primitive in the time of the dinosaurs, according to Grossnickle.

“But focusing on the Paleocene-Eocene radiation gives a distorted view of the history of mammals,” said Grossnickle. “It ignores many of the other groups of mammals and their relatives that were diversifying millions of years before then.”

Fossil discoveries over the past quarter century support the view summarized by Grossnickle and co-authors. Dinosaur-era mammaliaforms that were once known by only a single tooth or a few bone fragments are now represented by more-complete skeletons, which show the diversity in body shape, size, locomotion and diet.

“Now we can start to see the huge diversity of mammals and their relatives who lived alongside the dinosaurs,” said Grossnickle.

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For more information, contact Grossnickle at dmgrossn@uw.edu.

A new published April 30 in the identified three factors critical in the rise of mammal communities since they first emerged during the Age of Dinosaurs: the rise of flowering plants, also known as angiosperms; the evolution of tribosphenic molars in mammals; and the extinction of non-avian dinosaurs, which reduced competition between mammals and other vertebrates in terrestrial ecosystems.

Previously, mammals in the Age of Dinosaurs were thought to be a relatively small part of their ecosystems and considered to be small-bodied, nocturnal, ground-dwelling insectivores. According to this long-standing theory, it wasn’t until the about 66 million years ago, which wiped out all non-avian dinosaurs, that mammals were then able to flourish and diversify. An astounding number of fossil discoveries over the past 30 years has challenged this theory, but most studies looked only at individual species and none has quantified community-scale patterns of the rise of mammals in the Mesozoic Era.

Co-authors are Meng Chen, a 91̽�� alumnus and current postdoctoral researcher at Nanjing University; , a 91̽�� biology professor and curator of paleobotany at the UW’s ; and , a 91̽��associate professor of biology and Burke Museum curator of vertebrate paleontology. The team created a Rubik’s Cube-like structure identifying 240 “eco-cells” representing possible ecological roles of mammals in a given ecospace. These 240 eco-cells cover a broad range of body size, dietary preferences, and ways of moving of small-bodied mammals. When a given mammal filled a certain type of role or eco-cell, it filled a spot in the ‘Rubik’s Cube.’ This method provides the first comprehensive analysis of evolutionary and ecological changes of fossil mammal communities before and after K-Pg mass extinction.

“We cannot directly observe the ecology of extinct species, but body size, dietary preferences and locomotion are three aspects of their ecology that can be relatively easily inferred from well-preserved fossils,” said Chen. “By constructing the ecospace using these three ecological aspects, we can visually identify the spots filled by species and calculate the distance among them. This allows us to compare the ecological structure of extinct and extant communities even though they don’t share any of the same species.”

The team analyzed living mammals to infer how fossil mammals filled roles in their ecosystems. They examined 98 small-bodied mammal communities from diverse biomes around the world, an approach that has not been attempted at this scale. They then used this modern-day reference dataset to analyze five exceptionally preserved mammal paleocommunities ― two Jurassic Period and two Cretaceous Period communities from northeastern China, and one Eocene Epoch community from Germany. Usually Mesozoic Era mammal fossils are incomplete and consist of fragmentary bones or teeth. Using these remarkably preserved fossils enabled the team to infer ecology of these extinct mammal species, and look at changes in mammal community structure during the last 165 million years.

The team found that, in current communities of present-day mammals, ecological richness is primarily driven by vegetation type, with 41 percent of small mammals filling eco-cells compared to 16 percent in the paleocommunities. The five mammal paleocommunities were also ecologically distinct from modern communities and pointed to important changes through evolutionary time. Locomotor diversification occurred first during the Mesozoic, possibly due to the diversity of microhabitats, such as trees, soils, lakes and other substrates to occupy in local environments. It wasn’t until the Eocene that mammals grew larger and expanded their diets from mostly carnivory, insectivory and omnivory to include more species with diets dominated by plants, including fruit. The team determined that the rise of flowering plants, new types of teeth and the extinction of dinosaurs likely drove these changes.

Before the rise of flowering plants, mammals likely relied on conifers and other seed plants for habitat, and their leaves and possibly seeds for food. By the Eocene, flowering plants were both diverse and dominant across forest ecosystems. Flowering plants provide more readily available nutrients through their fast-growing leaves, fleshy fruits, seeds and tubers. When becoming dominant in forests, they fundamentally changed terrestrial ecosystems by allowing for new modes of life for a diversity of mammals and other forest-dwelling animals, such as birds.

“Flowering plants really revolutionized terrestrial ecosystems,” said Strömberg. “They have a broader range of growth forms than all other plant groups ― from giant trees to tiny annual herbs ― and can produce nutrient-rich tissues at a faster rate than other plants. So when they started dominating ecosystems, they allowed for a wider variety of life modes and also for much higher ‘packing’ of species with similar ecological roles, especially in tropical forests.”

Tribosphenic molars ― complex multi-functional cheek teeth ― became prevalent in mammals in the late Cretaceous Period. Mutations and natural selection drastically changed the shapes of these molars, allowing them to do new things like grinding. In turn, this allowed small mammals with these types of teeth to eat new kinds of foods and diversify their diets.

Lastly, the K-Pg mass extinction event that wiped out all dinosaurs except birds 66 million years ago provided an evolutionary and ecological opportunity for mammals. Small body size is a way to avoid being eaten by dinosaurs and other large vertebrates. The mass extinction event not only removed the main predators of mammals, but also removed small dinosaurs that competed with mammals for resources. This ecological release allowed mammals to grow into larger sizes and fill the roles the dinosaurs once had.

“The old theory that early mammals were held in check by dinosaurs has some truth to it,” said Wilson. “But our study also shows that the rise of modern mammal communities was multifaceted and depended on dental evolution and the rise of flowering plants.”

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For more information contact Andrea Godinez with the 91̽��Burke Museum at burkepr@uw.edu.

Burke Museum story .

An excavation site in North Dakota sheds new light on what happened when a giant meteorite struck planet Earth, 66 million years ago.

On that day, violent ground shaking first raised giant waves in the waters of an ancient inland sea. Then tiny beads began to fall, created from molten rock cooling at the edge of space to make glassy spheres. The rain of glass was so heavy it may have ignited much of the vegetation on land, while in the water, fish struggled to breathe as the glass beads clogged their gills.

Once the surge of water reached a river mouth, it transformed into a 30-foot wall of water, tossing hundreds if not thousands of freshwater fish — sturgeon and paddlefish — onto a sandbar and temporarily reversing the flow of the river.

Stranded by the receding water, the fish were pelted by glass beads up to 5 millimeters (almost a quarter of an inch) in diameter. Some beads got buried inches deep in the mud. Rocks and beads continued to rain down for another 10 to 20 minutes before a second large wave inundated the shore and covered the fish with gravel, sand and fine sediment, sealing them until the present-day discovery.

In a published April 1 in the an international team of authors, including 91̽�� Provost Mark Richards, share the discovery of a site that tells another piece of the story from the day a meteor strike is thought to have led to the end of the dinosaurs.

“It’s like a museum of the end of the Cretaceous in a layer a meter and a half thick,” said Richards, who is also a professor in the 91̽��.

This unique fossilized graveyard – fish stacked one atop another mixed with burned tree trunks and conifer branches, dead mammals, a pterosaur egg, a mosasaur and insects, the carcass of a Triceratops and seaweed and marine snails called ammonites – was unearthed over the past six years in the Hell Creek Formation in North Dakota by lead author .

“This is the first mass death assemblage of large organisms anyone has found associated with the KT boundary,” said DePalma, curator of paleontology at the Palm Beach Museum of Natural History in Florida and a doctoral student at the University of Kansas. “Nowhere else on Earth can you find such a collection consisting of a large number of species representing different ages of organisms and different stages of life, all of which died at the same time, on the same day.”

The new study describes the site, dubbed Tanis, and the evidence connecting it with the asteroid or comet strike off Mexico’s Yucatan Peninsula. That impact created a huge crater, called Chicxulub, on the ocean floor and sent vaporized rock and cubic miles of asteroid dust into the atmosphere.

The impact would have melted the bedrock under the seafloor and pulverized the asteroid, sending dust and melted rock into the stratosphere, darkening the sun for months if not years. Debris would have rained down from the sky.

Richards, who did the research as a professor and dean at the University of California, Berkeley, and , a UC Berkeley professor of the graduate school who first hypothesized that a comet or asteroid impact caused the mass extinction, analyzed the rain of glass beads and the tsunami-like waves that buried and preserved the fish. The beads, called tektites, formed in the atmosphere from rock melted by the impact.

Richards and Alvarez determined that the fish could not have been stranded and then buried by a typical tsunami, a single ocean wave that would have reached this previously unknown arm of the Western Interior Seaway hours after the impact 3,000 kilometers away, if at all. Their reasoning: The tektites would have rained down within 45 minutes to an hour of the impact, unable to create mudholes if the seabed had not already been exposed.

Instead, they argue, seismic waves likely arrived within 10 minutes of the impact from what would have been the equivalent of a magnitude 10 or 11 earthquake, creating a seiche (pronounced saysh) wave in the inland sea, similar to water sloshing in a bathtub during an earthquake.

Though large earthquakes often generate seiche waves in enclosed bodies of water, they’re seldom noticed, Richards said. For example the 2011 Tohoku quake in Japan, a magnitude 9.0, created 6-foot-high seiche waves a half hour later in a Norwegian fjord 8,000 kilometers away.

In the case of the Chicxulub impact, the timing works out for the seiche waves’ arrival.

“The seismic waves start arising within 9 to 10 minutes of the impact, so they had a chance to get the water sloshing before all the spherules had fallen out the sky,” Richards said. “These spherules coming in cratered the surface, making funnels — you can see the deformed layers in what used to be soft mud — and then rubble covered the spherules. No one has seen these funnels before.”

The tektites would have reached terminal velocity of about 200 miles per hour, according to Alvarez, who decades ago estimated the travel time of these objects through the atmosphere.

“You can imagine standing there being pelted by these glass spherules. They could have killed you,” Richards said. Many believe that the rain of debris ignited wildfires over the entire American continent, if not around the world.

Richards estimated that the seismic waves, creating the seiche waves, would arrive in North Dakota at roughly the same time as the projectiles from above.

At least two huge seiche waves inundated the land, perhaps 20 minutes apart, leaving six feet of deposits covering the fossils. Overlaying this material is a layer of clay rich in iridium, a metal rare on Earth but common in asteroids and comets. This layer is known as the KT or KPg boundary, marking the end of the Cretaceous Period.

“When we proposed the impact hypothesis to explain the great extinction, it was based just on finding an anomalous concentration of iridium — the fingerprint of an asteroid or comet,” said Alvarez. “Since then the evidence has gradually built up. But it never crossed my mind that we would find a deathbed like this.”

The new discovery at Tanis is the first time the debris produced in the impact was found along with animals killed in the impact’s immediate aftermath.

Jan Smit, a retired professor of paleontology from the Vrije Universiteit in Amsterdam in The Netherlands, who is considered the world expert on tektites from the impact, analyzed and dated the tektites from the Tanis site. Many tektites were found in near-perfect condition embedded in amber.

“We have an amazing array of discoveries which will prove in the future to be even more valuable,” Smit said. “We have fantastic deposits that needs to be studied from all different viewpoints. And I think we can unravel the sequence of incoming ejecta from the Chicxuulab impact in great detail, which we would never have been able to do with all the other deposits around the Gulf of Mexico.”

Co-authors are David Burnham of the University of Kansas, Klaudia Kuiper of Vrije Universiteit, Phillip Manning of the College of Charleston in South Carolina, Anton Oleinik of Florida Atlantic University, Peter Larson of the Black Hills Institute of Geological Research in South Dakota, Florentin Maurrasse of Florida International University, Johan Vellekoop of KU Leuven in Belgium and Loren Gurche of the Palm Beach Museum of Natural History.

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Adapted from a UC Berkeley . See also a University of Kansas . Reporters can contact Richards through Hannah Hickey (206-543-2580/hickeyh@uw.edu).

Antarctica wasn’t always a frozen wasteland. About 250 million years ago, it was covered in forests and rivers, and the temperature rarely dipped below freezing. It was also home to diverse wildlife, including early relatives of the dinosaurs. Scientists have just discovered the newest member of that family — an iguana-sized reptile whose genus name, Antarctanax, means “Antarctic king.”

“This new animal was an archosaur, an early relative of crocodiles and dinosaurs,” said Brandon Peecook, a researcher and lead author of a in the describing the new species. “On its own, it just looks a little like a lizard, but evolutionarily, it’s one of the first members of that big group. It tells us how dinosaurs and their closest relatives evolved and spread.”

Collected during a 2010-2011 expedition to Antarctica led by senior author , professor of biology at the 91̽�� and curator of vertebrate paleontology at the UW’s , the fossil specimen consists of portions of the backbone, limbs and skull. The specimen is now part of the permanent collections at the Burke Museum and is one of more than 300 vertebrate fossils from Antarctica in its collection, collected over the course of four expeditions and resulting in one of the largest Antarctic vertebrate fossil collections in the country. During the Burke’s most recent Antarctic expedition in 2017-2018 Sidor led his team back to Graphite Peak, the site where Antarctanax had been found, which was also where the first vertebrate fossils in Antarctica were discovered in 1967.

Although the new specimen is an incomplete skeleton, paleontologists still have a good feel for the animal, named Antarctanax shackletoni — the latter part a nod to polar explorer . Based on its similarities to other fossil animals, the researchers surmise that Antarctanax was a carnivore that hunted bugs, amphibians, and relatives of early mammals.

The most interesting thing about Antarctanax, the authors say, is where and when it lived.

“The more we find out about prehistoric Antarctica, the weirder it is,” says Peecook, who was a doctoral student in the 91̽��Department of Biology at the time the fossil was collected and is now also a research associate at the Burke Museum. “We thought that Antarctic animals would be similar to the ones that were living in southern Africa, since those landmasses were joined back then. But we’re finding that Antarctica’s wildlife is surprisingly unique.”

About two million years before Antarctanax lived — the blink of an eye in geologic time — Earth underwent its largest mass extinction. Climate change, caused by volcanic eruptions, killed 90 percent of animal life. The years immediately after that extinction event were an evolutionary free-for-all. With the slate wiped clean by the mass extinction, new groups of animals vied to fill the gaps. The archosaurs, including dinosaurs, were among the groups that experienced enormous growth.

“Before the mass extinction, archosaurs were only found around the equator, but after it, they were everywhere,” said Peecook. “And Antarctica had a combination of these brand-new animals and stragglers of animals that were already extinct in most places — what paleontologists call ‘dead walking.’ You’ve got tomorrow’s animals and yesterday’s animals, cohabiting in a cool place,” he added.

“Fossil exploration in Antarctica is really difficult, given all of the logistics involved. But since so little work has been done the potential for making important new discoveries is high — and that’s what Antarctanax represents,” said Sidor. “The same rocks that yielded Antarctanax also yield some of the earliest mammal relatives from after the mass extinction.”

The fact that scientists have found Antarctanax helps bolster the idea that Antarctica was a place of rapid evolution and diversification after the mass extinction.

“The more different kinds of animals we find, the more we learn about the pattern of archosaurs taking over after the mass extinction,” said Peecook. “Antarctica is one of those places on Earth, like the bottom of the sea, where we’re still in the very early stages of exploration. Antarctanax is our little part of discovering the history of Antarctica.”

Co-author on the paper is of the University of the Witwatersrand in Johannesburg and the Iziko South African Museum.

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For more information, contact Andrea Godinez at burkepr@uw.edu.

Adapted from a by the Field Museum.

The lecture is Tuesday, Oct. 30, at 3:30 p.m. in the HUB Lyceum. It will also be and available afterward online.

How did you get into studying dinosaurs? How does it relate to your expertise in Earth sciences?

The answer is, honestly, that I really don’t study dinosaurs. I’m not a paleontologist; I’m a geophysicist. I study the events that led to their extinction.

My expertise is in flood volcanism, caused by plumes of hot rock coming from deep in the interior up to the surface in what are called flood basalts. Mantle plumes also create features like Iceland or the Hawaiian Islands chain or the Galapagos Islands.

The last four mass extinctions on Earth are all closely associated in time with huge flood-basalt volcanic events. The largest mass extinction event was 251 million years ago, when about 90 percent of all species were wiped out. That event is very closely associated with a huge set of volcanic eruptions in Russia — the Siberian Traps eruptions.

Only the most recent mass extinction — the that killed the dinosaurs — is associated with a meteorite impact, the Chicxulub impact. The meteorite impact coincides almost exactly in time with the extinction event. But there was also flood volcanism at that time in India, creating the . Why does the dinosaur extinction coincide with a big meteorite, and is it related to the volcanism? This has been a real conundrum in the science.

The Deccan volcanism had started before the impact, so the meteorite didn’t cause the volcanism. But what I and my group have proposed, and found increasing evidence for, is that the rate of volcanism increased by a factor of two or three at the moment of impact. In this case, it looks like there was an ongoing flood-basalt event whose activity was accelerated by the meteor impact. And we propose that the acceleration of the eruptions may have contributed to the K-T extinction 66 million years ago, when 70 percent of everything in the fossil record was wiped out.

So let’s jump to the question that everyone’s inner 8-year-old wants to know, and that is the title of your talk: What killed the dinosaurs?

Not to give away the answer, but the truth is that we don’t quite know. We know that it’s one of two things — meteor impact or volcanism — and the two events may have been related. It leaves us, right now, not knowing which of those two events was the leading cause of the extinction. My own prejudice is that it probably was the impact, but we just don’t know that yet.

Have these been the only explanations for how the dinosaurs died out?

People today seem to think that we always knew there were mass extinctions. But that’s not true. Very few people realize that prior to 1980, the majority of paleontologists did not believe in mass extinctions. They had all sorts of other explanations for how species had disappeared. Dinosaurs were fairly large and rare as animals go, so it’s not entirely obvious from the fossil record that they died off suddenly. There are some people even today who maintain that the dinosaurs died off gradually.

But in 1980, Walter Alvarez and his group at the University of California, Berkeley, published this with evidence of an asteroid impact at the time of the K-T extinctions. That paper and the huge controversy surrounding it gave a lot of paleontologists the idea that there could be at least one major event that could trigger extinctions across the globe. When later in 1991 scientists discovered the in the Yucatán, Mexico, people became very convinced that mass extinction events were possible.

Since then, paleontology has gotten better and better, and it’s now clear that there are at least five, and possibly six, mass extinction events in the past 600 million years of Earth’s history. The four that have happened since 260 million years ago are very clear in the fossil record.

How do you carry out your research?

What I’ve been studying is the causal mechanism of the K-T mass extinction. I’m mainly concerned about the volcanic processes, and how they change the conditions for life on Earth. That involves understanding the nature and timing of the Deccan eruptions.

For the last four years, our team has been going to India to the Deccan Traps lavas to obtain samples. Prior to the work that we’ve done, the dating had only been precise to about half a million years. But by using the latest methods for , we can now date samples to a precision of about 30,000 years. This new technique has allowed us to say with increasing precision exactly when each lava sequence was laid down in layered rock formations that are about 3.5 kilometers (more than 2 miles) in total thickness.

We can also say rather precisely when the Chicxulub impact occurred. And we see profound changes in the nature of the volcanism in India just at that time. The Chicxulub impact caused a magnitude-11 earthquake, which we think triggered accelerated volcanism almost halfway around the world.

We had a very precise hypothesis that we were testing, and it’s turned out to be spectacularly confirmed. That doesn’t happen very often in science.

What should people expect from your talk?

The talk is designed for a general audience. I’m going to minimize the technical slides, and emphasize the places traveled, the adventure of it all, the people I’ve worked with, and highlight the most important scientific aspects on the way.

It’s unusual to introduce a provost with a research talk. Was that a deliberate choice?

��Yes. I very much want the faculty and students here to feel that I’m part of the academic mission of the university, and not just someone who lords over their budgets. (Yes, you can actually keep that line.)

The role of provost is mysterious to many people. How do you like to describe it?

��Officially, the provost is the chief academic and budget officer for the campus. It’s a huge amount of responsibility, especially for a place this large and complex. So, one way to think about it is that the president and the provost are both chief administrators, with the president as the boss and the provost beneath.

The president is a much more outward-looking person, who is the face of the university and is more publicly and politically visible. The provost is the person who’s more inwardly focused and looking at the running of the enterprise. President Ana Mari Cauce and I talk every day, and we don’t make major decisions without consulting each other. It’s really a partnership.

How do you balance your research with being provost, and why do you think it’s important to do both?

��I’ve had a lot of practice. I was dean for 12 years at Berkeley, and managed to keep my research going during that time. It’s mainly an issue of time management.

I think it’s important, if you’re in a position like dean or provost, for faculty to see you as a colleague. The main way to be seen as a colleague is to be a teacher or a researcher. Keeping a research program, which you can schedule during “off-hours,” is much more possible than maintaining a regular teaching schedule.

On the provost front, any areas that people should look for as initial priorities?

Some things that I think need renewed attention at the 91̽��— in no particular order — are support for graduate students and restoration of infrastructure and facilities. Affordability for undergraduate students and the overall undergraduate experience, and diversity across all aspects of the university community, especially among the faculty are also significant priorities.

Anything else you would like to say to the university community?

��It’s an exciting university that is innovative and flexible, and I’m really happy to be here.

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After a great mass extinction shook the world about 252 million years ago, animal life outside of the ocean began to take hold. The earliest mammals entered the scene, and reptiles — including early dinosaurs — lived on Pangea, the name given to the giant landmass in which all of the world’s continents were joined as one.

A project spanning countries, years and institutions has attempted to reconstruct what the southern end of this world looked like during this period, known as the Triassic (252 to 199 million years ago). Led by paleontologists and geologists at the 91̽��, the team has uncovered new fossils in Zambia and Tanzania, examined previously collected fossils and analyzed specimens in museums around the world in an attempt to understand life in the Triassic across different geographic areas.

Findings from the past decade of fieldwork and analysis are reported March 28 in a publication of the . In total, 13 research papers detailing new fossils, geologic discoveries and ecological findings in the Triassic make up the society’s 2018 special-edition volume, published once a year in a competitive submission process.

“Most of what we know about the major mass extinction is from the South African Karoo Basin. I was always interested in understanding, do we see the exact same pattern around the world, or do we not?” said co-editor , a 91̽��biology professor and curator of vertebrate paleontology at the Burke Museum of Natural History and Culture.

“The fossil record can be great to understand timing and sequence, but not always great at looking at things in a geographic context.”

Since 2007, Sidor and his team of students, postdoctoral researchers, paleontologists and geologists have visited the Ruhuhu Basin of Tanzania five times and the Luangwa and mid-Zambezi basins of Zambia four times. They lived there for about a month at a time, often hiking for miles to find fossil sites and camping in villages and national parks. Once, they were even awakened by the stomping and calls of elephants only feet from their camp.

Each site in Tanzania and Zambia contains its own collection of fossils from the Triassic and other periods, but the goal of this decade-long project was to look across locations hundreds and thousands of miles apart to find similarities in the fossil records. Two papers describe the regional patterns and similarities across much of what used to be Pangea.

“These papers highlight what a regional perspective we now have — we have the same fossils from Tanzania, Antarctica, Namibia and more,” Sidor said. “We’re getting a much better Southern Hemisphere perspective of what’s going on in the Triassic.”

Most of the papers in the special edition discuss new fossil findings from the paleontological digs. One explains the discovery of a new species of lizard-like reptile called a procolophonid. Another details Teleocrater, an early dinosaur relative that walked on four crocodile-like legs. This finding in Nature last year, but the new paper describes the animal’s anatomy in fuller detail.

Most of the remaining papers describe other animals that were present in the Triassic besides the early dinosaurs.

“This was a time when dinosaurs were just stepping onto the stage, and they were not very big and not very remarkable animals then,” Sidor said. “These papers really round out what dinosaurs were competing with before they became the dominant reptiles on land.”

In addition to the 13 papers that make up the special edition, the team has published 24 peer-reviewed papers as part of this project in the past decade.

More than 2,200 fossils were collected across Tanzania and Zambia over the last decade of fieldwork. Of the special edition’s 27 authors, many participated in fieldwork with Sidor since 2007, including co-editor , a former postdoctoral researcher at the 91̽��and now an assistant professor at Virginia Tech.

Fossil hunting is an experience every member of Sidor’s lab can have, from undergraduates through postdoctoral researchers. Sidor and a team are going again this August.

“This has been what my lab has done, and all of my students have been involved in some way,” he said. Four of Sidor’s students and two postdoctoral researchers are co-authors of papers in the new special edition.

Other co-authors are from The Field Museum; London’s Natural History Museum; University of Birmingham; Virginia Tech; Royal Ontario Museum; California Academy of Sciences; Southern Methodist University; Petrified Forest National Park; Iziko: South African Museum; Muséum national d’Histoire naturelle (Paris); University of Chicago; University of the Witwatersrand; National Museum (Bloemfontein); Museo Argentino de Ciencias Naturales; Rowan University; and North Carolina Museum of Natural Sciences.

Fieldwork in Tanzania and Zambia was supported by the National Science Foundation, the��National Geographic Society, The Grainger Foundation and The Field Museum/IDP Foundation, Inc., African Partners Program. Additional support for analysis and museum research are noted in the individual papers.

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For more information, contact Sidor at casidor@uw.edu.

Images available for download: https://drive.google.com/drive/folders/1IguAX2X2tFS5oC3Rnq7nv4mR6hupPQa7?usp=sharing

Paleontologists picking through a bounty of fossils from Montana have discovered something unexpected —��a new species of lizard from the late dinosaur era, whose closest relatives roamed in faraway Asia.

This ancient lizard, which lived 75 million years ago in a dinosaur nesting site, is described from stem to stern in published Jan. 25 in the . Christened Magnuviator ovimonsensis, the new species fills in significant gaps in our understanding of how lizards evolved and spread during the dinosaur era, according to paleontologists at the 91̽�� and the who led the study.

“It is incredibly rare to find one complete fossil skeleton from a relatively small creature like this lizard,” said , lead author and postdoctoral research associate in the 91̽��biology department and the Burke Museum. “But, in fact, we had two specimens, both from the same site at Egg Mountain in Montana.”

Right out of the gate, Magnuviator is reshaping how scientists view lizards, their biodiversity and their role in complex ecosystems during this reptile’s carefree days in the Cretaceous Period 75 million years ago.

Based on analyses of the nearly complete fossil skeletons, Magnuviator was an ancient offshoot of iguanian lizards —��and they’re actually the oldest, most complete iguanian fossils from the Americas. Today, iguanians include of the Old World, and in the American tropics and even the infamous water-walking —��or “Jesus Christ” —��lizards. But based on its anatomy, Magnuviator was at best a distant relative of these modern lizard families, most of which did not arise until after the non-avian dinosaurs —��and quite a few lizards and other creatures —��went extinct 66 million years ago.

The team came to these conclusions after meticulous study of both Egg Mountain specimens over four years. This included a round of CT scans at Seattle Children’s Hospital to narrow down the fossil’s location within a larger section of rock and a second round at the American Museum of Natural History to digitally reconstruct the skull anatomy. The fact that both skeletons were nearly complete allowed them to determine not only that Magnuviator represented an entirely new species, but also that its closest kin weren’t other fossil lizards from the Americas. Instead, it showed striking similarities to other Cretaceous Period iguanians from Mongolia.

“These ancient lineages are not the iguanian lizards which dominate parts of the Americas today, such as anoles and horned lizards,” said DeMar. “So discoveries like Magnuviator give us a rare glimpse into the types of ‘stem’ lizards that were present before the extinction of the dinosaurs.”

But Magnuviator‘s surprises don’t end with the Mongolian connection. The site of its discovery is also eye-popping.

Egg Mountain is already famous among fossil hunters. Over 30 years ago, paleontologists discovered the first fossil remains of dinosaur babies there, and it is also one of the first sites in North America where dinosaur eggs were discovered.

“We now recognize Egg Mountain as a unique site for understanding Cretaceous Period ecosystems in North America,” said senior author , 91̽��associate professor of biology and curator of paleontology at the Burke Museum. “We believe both carnivorous and herbivorous dinosaurs came to this site repeatedly to nest, and in the process of excavating this site we are learning more and more about other creatures who lived and died there.”

The team even named their new find as homage to its famous home and its close lizard relatives in Asia. Magnuviator ovimonsensis means “mighty traveler from Egg Mountain.”

Through excavations at Egg Mountain led by co-author at Montana State University and meticulous analysis of fossils at partner institutions like the 91̽��and the Burke Museum, scientists are piecing together the Egg Mountain ecosystem of 75 million years ago. In those days, Egg Mountain was a semi-arid environment, with little or no water at the surface. Dinosaurs like the duck-billed and the birdlike, carnivorous nested there.

Researchers have also unearthed fossilized mammals at Egg Mountain, which are being studied by Wilson’s group, as well as wasp pupae cases and pollen grains from plants adapted for dry environments. Based on the structure of Magnuviator‘s teeth, as well as the eating habits of some lizards today, the researchers believe that it could have feasted on wasps at the Egg Mountain site. Though based on its relatively large size for a lizard —��about 14 inches in length —��Magnuviator could have also eaten something entirely different.

“Due to the significant metabolic requirements to digest plant material, only lizards above a certain body size can eat plants, and Magnuviator definitely falls within that size range,” said DeMar.

Whatever its diet, Magnuviator and its relatives in Mongolia did not make it into the modern era. DeMar and co-authors hypothesize that these stem lineages of lizards may have gone extinct along with the non-avian dinosaurs. But given the spotty record for lizards in the fossil record, it will take more Magnuviator-level discoveries to resolve this debate. And, unfortunately, part of the excitement surrounding Magnuviator is that it is a rare find.

Other co-authors are the late Jack Conrad of the New York Institute of Technology and the American Museum of Natural History and of the University of Cambridge. The research was funded by the National Science Foundation and the American Museum of Natural History.

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For more information, contact DeMar at ddemar@uw.edu or 206-543-4832 and Wilson at gpwilson@uw.edu or 206-543-8917.

DOI: 10.1098/rspb.2016.1902

Grant numbers: 0847777, 1325674.

Move over, hyenas and saber-toothed cats; there’s a mammal with an even stronger bite. A new study by paleontologists at the and the 91̽�� describes an early marsupial relative called Didelphodon vorax that lived alongside dinosaurs and had, pound-for-pound, the strongest bite force of any mammal ever recorded.

in the journal , the team’s findings suggest mammals were more varied during the age of dinosaurs than previously believed. Didelphodon was able to eat a variety of foods and was likely a scavenger-predator who could eat prey ranging from snails to small dinosaurs.

In addition, the team re-traced the origins of marsupials. Previous theories attribute South America as the origin of marsupials, but anatomical features of the Didelphodon point to marsupials originating in North America 10 to 20 million years earlier than originally thought and later dispersing and diversifying in South America.

“What I love about Didelphodon vorax is that it crushes the classic mold of Mesozoic mammals,” , Burke Museum adjunct curator of vertebrate paleontology and 91̽��associate professor of biology. “Instead of a shrew-like mammal meekly scurrying into the shadows of dinosaurs, this badger-sized mammal would’ve been a fearsome predator on the Late Cretaceous landscape — even for some dinosaurs.”

All of these findings are made possible by four fossil specimens recently discovered in the 66 to 69 million-year-old deposits of the Hell Creek Formation in Montana and North Dakota. Prior to these discoveries, the 60 known species of metatherians (marsupials and their closest relatives) from the Cretaceous of North America — including Didelphodon — were almost all identified through fragments of jaw bones or teeth, providing a limited glimpse into marsupials’ closest relatives. These four fossils include a nearly-complete skull from the North Dakota Geological Survey State Fossil collection, a partial snout and an upper jaw bone from the Burke Museum’s collections, and another upper jaw from the Sierra College Natural History Museum.

By analyzing never-before-seen parts of Didelphodon‘s anatomy, Wilson and his colleagues were able to determine these marsupial relatives were about the size of today’s and were the largest metatherian from the Cretaceous. With a nearly complete skull to measure, they were able to estimate the overall size of Didelphodon, which ranged from 5.3 to 11.5 pounds.

To test the bite force of Didelphodon, , then a 91̽��Biology research technician working with 91̽��biology professor and Burke Museum curator , CT-scanned the fossils and compared the gaps in reconstructed skulls where jaw muscles would go to those of present-day mammals with known bite forces. Bite force measurements indicate that, pound-for-pound, Didelphodon had the strongest bite force of any mammal that has ever lived. In addition to the bite force, Didelphodon‘s canines were similar to living felines and hyenas — suggesting they could handle biting into bone, biting deep and killing prey. Its shearing molars and big rounded premolars, combined with powerful jaws and jaw muscles, indicate it had a specific niche in the food web as a predator or scavenger capable of crushing hard bone or shells, and was capable of eating prey as big as it was — even possibly small dinosaurs.

“I expected Didelphodon to have a fairly powerful bite based on the robust skull and teeth, but even I was surprised when we performed the calculations and found that, when adjusted for body size, it was capable of a stronger pound-for-pound bite than a hyena,” said Vander Linden, who is now a graduate student at University of Massachusetts Amherst. “That’s a seriously tough mammal.”

Co-author , former 91̽��biology graduate student and now a visiting assistant professor at Bucknell University, also examined “microwear” patterns, or tiny pits and scratches on the specimens’ teeth, to indicate what the animals were eating as their “last suppers” a few days before the animals died. By comparing the microwear patterns from Didelphodon to the teeth of other fossilized species and current-day mammals from the Burke’s mammal collection, Calede found Didelphodon was an omnivore that likely consumed a range of vertebrates, plants and hard-shelled invertebrates like mollusks and crayfish, but few insects, spiders, earthworms or leeches.

“The interesting thing about these fossils is that they allowed us to study the ecology of Didelphodon from many angles,” said Calede. “The strength of the conclusions come from the convergence of microwear with bite force analysis, studies of the shape and breakage of the teeth, as well as the shape of the skull as a whole.”

The newly-described skull features on these fossils also provided clues that help clarify the origin of all marsupials. The team found five major lineages of marsupial ancestors and marsupials themselves diverged in North America 85 to 100 million years ago. Marsupial relatives also got larger and ate a wider variety of foods, which coincides with an increase in diversity of other early mammals and flowering plants. Most of this North American diversity was then lost gradually starting 79 million years ago, before abruptly dropping during the 66 million years ago that also killed the dinosaurs. Around this time, marsupials’ diversity and evolution shifted to South America.

“Our study highlights how, despite decades of paleontology research, new fossil discoveries and new ways of analyzing those fossils can still fundamentally impact how we view something as central to us as the evolution of our own clade, mammals,” said Wilson.

Other co-authors were Eric Ekdale with San Diego State University and John Hoganson with the North Dakota Geological Survey. The research was funded by the 91̽�� and the National Science Foundation.

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For more information, contact Andrea Godinez at burkepr@uw.edu.

Adapted from by the Burke Museum.

Burke Museum researchers discovered the fossil while collecting fossils (a creature with a spiral shell) from a marine rock area known as the Cedar District Formation. The researchers first noticed a small section of exposed bone on the surface of the rocks, then returned with a team of paleontologists to help excavate the fossil so it could be studied at the Burke Museum.

, the museum’s curator of vertebrate paleontology and a biology professor and 91̽�� graduate student describe the find in a published May 20 in the journal PLOS ONE. The fossil is a partial left femur of a theropod dinosaur, the group of two-legged, carnivorous dinosaurs that includes Velociraptor, Tyrannosaurus rex and modern birds.

The fossil is 16.7 inches long and 8.7 inches wide. Because the fossil is incomplete, paleontologists aren’t able to identify the exact family or species it belonged to. However, Sidor and Peecook compared the fossil to other museums’ specimens and were able to calculate that the complete femur would have been more than 3 feet long — slightly smaller than a T. rex femur. The fossil is from the period and is approximately 80 million years old.

Sidor and Peecook determined that although incomplete, the femur is from a theropod dinosaur for two reasons: First, the hollow middle cavity of the bone (where marrow was present) is unique to theropods during this period; and second, a feature on the surface of the bone (the fourth trochanter) is prominent and positioned relatively close to the hip, which is a combination of traits known only in theropod dinosaurs.

“This fossil won’t win a beauty contest,” Sidor said. “But fortunately it preserves enough anatomy that we were able to compare it to other dinosaurs and be confident of its identification.”

“The fossil record of the West Coast is very spotty when compared to the rich record of the interior of North America,” Peecook said. “This specimen, though fragmentary, gives us insight into what the West Coast was like 80 million years ago, plus it gets Washington into the dinosaur club.”

Washington is now the 37th state where dinosaurs have been found.

Fossilized prehistoric clams were also found inside the hollow part of the bone, which indicates the dinosaur fossilized in marine rock. These additional fossils are a rare occurrence and provide scientists with a snapshot of other lifeforms that were present where the dinosaur fossilized.

The accompanying fossilized clams are so well preserved that Burke paleontologists were able to identify the species, Crassatellites conradiana. These clams lived in shallow water, so it’s likely the dinosaur died near the sea, was tossed by the waves, and eventually came to rest among the clams.

“This is a very exciting discovery,” said Lisa Lantz, stewardship manager for the Washington State Parks and Recreation Commission. “It underscores the importance of protecting natural places for the long-term benefit of the public — not only for recreation, but for important scientific research.”

More information about the fossil:

Why have no dinosaurs been found in Washington state until now?

Dinosaurs are found in rocks from the time periods in which they lived (240–66 million years ago). Washington state was mostly underwater during this period, so Washington has very little exposed rock of the right age. Because dinosaurs were land animals, it is very unusual to find dinosaur fossils in marine rocks—making this fossil a rare and lucky discovery.

How did the dinosaur get to Sucia Island State Park?

Eighty million years ago, the rocks that today form Sucia Island were likely deposited farther south. How much farther south is a topic of scientific debate, with locations ranging between present-day Baja California, Mexico, and Northern California. Earthquakes and other geologic forces that constantly reshape our planet moved the rocks north to their present-day location.

Why is the fossil at the Burke Museum?

The Burke Museum is the state’s museum for natural history and culture. Burke Museum paleontologists were issued scientific collecting permits by Washington State Parks prior to excavating the fossil. Fossil exploration and collection on state land is legal only with proper permits issued for legitimate scientific research. Any items discovered in permitted scientific exploration are considered publicly owned and remain the property of Washington State Parks collections. The fossil is held in trust by the Burke Museum on behalf of State Parks.

State Parks provides interpretation of natural and cultural resources and regularly partners with the Burke Museum to study, curate and share Washington’s natural and cultural heritage.

When can the public see the fossil?

Washington’s first dinosaur fossil will be on display in the Burke Museum’s lobby beginning Thursday, May 21.

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For high resolution images and interviews, contact burkepr@uw.edu or 206-543-9762.