As Earth faces unprecedented climate change, a look into the planet’s deep past may provide vital insights into what may lie ahead. But knowledge of the natural world millions of years ago is fragmented.

A 15-year study of a site in Bolivia by a joint U.S.-Bolivia team has provided a comprehensive view of an ancient ecosystem when Earth was much warmer than it is today. The researchers’ findings online Nov. 1 by the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

Located in the Andes Mountains of southern Bolivia, the site, known as the — or QHB — was deposited 13 million years ago during the Miocene Epoch, when Earth’s climate was rebounding from a prior period of warming. Globally, temperatures were 3-4 degrees Celsius warmer than today, and mammal biodiversity was increasing markedly.

Today, the site is 11,500 feet above sea level. Back in the Miocene, the site was lower, but exactly how much was a matter of debate. Previous studies using geochemical methods estimated that the Miocene QHB was relatively high, close to 10,000 feet. But the team’s new findings, based on careful analysis of plant and animal fossils and other features at the site, favor an alternative theory: That the Miocene QHB was at a much lower elevation, likely less than 3,000 feet.

“Our new data indicates that this area was once covered by mosaic vegetation with a mix of trees, including palms, bamboos and other grasses,” said lead author , a 91̽�� professor of biology. “Although this vegetation lacks a good comparison in today’s South America, it was likely most similar to modern neotropical dry forest or wooded savanna growing at low elevation.”

A lower-elevation Miocene QHB site has potentially global consequences.

“When put together with previous work at QHB, our study — including looking at fossil soils, turtles and other ectothermic vertebrates, and mammal ecologies — suggests that the��Central Andes still had not undergone substantial uplift by 12 million years ago,” said Strömberg. “This is important because it helps us understand when this major mountain chain formed. The rise of the Andes is thought to have contributed to making tropical South America the most biodiverse area on Earth.”

Understanding ecosystems of the past can help predict what might happen in the future due to human-related climate change.

“Sites like this one in Bolivia are essential for helping us calibrate climate models,” said co-author and project leader , professor of anatomy at Case Western Reserve University. “Our understanding of climate change is based on models, and those models are based on information from the past.”

Between 2007 and 2017, Croft and co-author Frederico Anaya, a professor of geology at Universidad Autonóma Tomás Frías in Bolivia, led six international teams to the QHB to collect fossils. Despite its warmer, forested past, the site today is a high-altitude desert grassland.

During those trips, the team found many different types of fossils: bones and teeth of mammals and other vertebrates, microscopic plant remains, ancient soils, and tracks and traces of insects and other invertebrates. Analyzing these fossils contributed to the researchers’ conclusion that the Miocene QHB was at a lower elevation. For example, fossils from “cold-blooded” animals found at the site — a giant tortoise, a side-necked turtle and a very large snake — suggest the site’s elevation when these animals lived was less than 3,000 feet, based on modern-day distributions of closely related species.

Strömberg studied fossilized phytoliths from QHB. These are microscopic pieces of silica found in the cells and cell walls of plants, and the shapes of phytoliths differ depending on the type of plant they came from. She compared the fossilized phytoliths with those found in contemporary vegetation to identify the assortment of plants at the site during the Miocene.

Layers of volcanic ash and magnetic signatures in rocks at QHB allowed the fossils to be accurately dated. The diversity of preserved material allowed the team to make detailed reconstructions of the plants and animals and their living conditions. The team named 13 new species of fossil mammals based on remains from the site, including marsupials, hoofed mammals, rodents and armadillos. Most of the species have not been found anywhere else in South America and have no modern descendants.

“Nature has a wide variety of body plans, often much greater than the limited variety we see today,” said co-author Russell Engelman, a Case Western Reserve University graduate student who worked on the mammal fossils.

Moving forward, Croft is hoping to study another Bolivian Miocene site of a similar age, but over a longer time period.

“We are getting into uncharted territory in terms of climate, and you have to go deeper in time to get conditions that are similar,” said Croft.

Other co-authors are Beverly Saylor, Case Western Reserve University professor of Earth, environmental and planetary sciences; Angeline Catena, geology professor at Diablo Valley Community College in California; and Daniel Hembree, professor of Earth and planetary sciences at the University of Tennessee. The research was funded by the National Science Foundation.

For more information, contact Strömberg at caestrom@uw.edu.

Adapted from a by Case Western Reserve University.

This diversity can be deceiving, at least when it comes to how mammals create the next generation. Based on how they reproduce, nearly all mammals alive today fall into one of two categories: and . Placentals, including humans, whales and rodents, have long gestation periods. They give birth to well-developed young — with all major organs and structures in place — and have relatively short weaning periods, or lactation periods, during which young are nursed on milk from their mothers. Marsupials, like kangaroos and opossums, are the opposite: They have short gestation periods — giving birth to young that are little more than fetuses — and long lactation periods during which offspring spend weeks or months nursing and growing within the mother’s pouch, or marsupium.

For decades, biologists saw the marsupial way of reproduction as the more “primitive” state, and assumed that placentals had evolved their more “advanced” method after these two groups diverged from one another. But new research is testing that view. In a published July 18 in The American Naturalist, a team led by researchers at the 91̽�� and its present evidence that another group of mammals — the extinct — likely reproduced in a placental-like manner. Since multituberculates split off from the rest of the mammalian lineage before placentals and marsupials evolved, these findings question the view that marsupials were “less advanced” than their placental cousins.

“This study challenges the prevalent idea that the placental reproductive strategy is ‘advanced’ relative to a more ‘primitive’ marsupial strategy,” said lead author , a postdoctoral researcher at the University of Michigan who conducted this study as a 91̽��doctoral student. “Our findings suggest that placental-like reproduction either is the ancestral reproductive route for all mammals that give birth to live young, or that placental-like reproduction evolved independently in both multituberculates and placentals.”

Multituberculates arose about 170 million years ago in the Jurassic. Most were small-bodied creatures, resembling rodents. For much of their history, multituberculates were the most abundant and diverse group of mammals. But scientists know very little about their life history, including how they reproduced, because of their generally poor fossil record. The last multituberculates died out about 35 million years ago.

Weaver reasoned that the microscopic structure of fossilized bone tissues can house useful life-history information about multituberculates, such as their growth rate. Working under co-author , a 91̽��professor of biology and curator of vertebrate paleontology at the Burke Museum, Weaver and his colleagues obtained cross sections of 18 fossilized femurs — the thigh bone — from multituberculates that lived approximately 66 million years ago in Montana.

All 18 samples showed the same structural organization: a layer of disorganized bone “sandwiched” between an inner and outer layer of organized bone. Disorganized bone, or woven bone, indicates rapid growth and is so named because, under a microscope, the layers of bone tissue are laid out in a crisscrossed fashion. In organized bone, which reflects slower growth, layers are parallel to one another.

The researchers then examined femoral cross sections taken from 35 small-bodied mammalian species that are living today — 28 placentals and seven marsupials, all from Burke Museum collections. Nearly all of the placental femurs showed the same “sandwich” organization as the multituberculates. But all of the marsupial femurs consisted almost entirely of organized bone, with only a sliver of disorganized bone.

The team believes that is stark difference likely reflects their divergent life histories.

“The amount of organized bone in the outermost layer, or cortex, of the femur strongly correlates with the length of the lactation period,” said Weaver. “Marsupials have long lactation periods and a lot of organized bone in the outermost cortex. The opposite is true for placentals: a short lactation period and much less organized bone in the outermost cortex.”

The outermost layer of organized bone was laid down after birth as the femur’s diameter increased. For tiny marsupial newborns, bones must grow much more to reach adult size, so they deposit a greater amount of outer organized bone compared to placentals, according to Weaver.

“This is compelling evidence that multituberculates had a long gestation and a short lactation period similar to placental mammals, but very different from marsupials,” said Weaver.

Based on this correlation, the researchers estimate that multituberculates had a lactation period of approximately 30 days — similar to today’s rodents.

These findings cast further doubt on an old view that marsupials have a “more primitive” and placentals a “more advanced” reproductive strategy. The common ancestor of multituberculates, placentals and marsupials may have had a placental-like mode of reproduction that was retained by placentals and multituberculates. Alternatively, multituberculates and placentals could have evolved their long-gestation and short-lactation reproductive methods independently.

Future studies of multituberculate life history may clarify which explanation is true, as well as other outstanding questions of this, and other, ancient branches of our mammalian family tree.

“The real revelation here is that we can cut open fossil bones and examine their microscopic structures to reconstruct the intimate life history details of long-extinct mammals,” said Wilson Mantilla. “That’s really incredible to me.”

Additional co-authors are former 91̽��undergraduate researcher Henry Fulghum, now a graduate student at Indiana University; 91̽��postdoctoral researcher David Grossnickle; 91̽��graduate students William Brightly and Zoe Kulik; and Megan Whitney, a 91̽��doctoral alum and current postdoctoral researcher at Harvard University. The research was funded by the National Science Foundation, the UW, the Burke Museum, the Society of Vertebrate Paleontology, the Paleontological Society and the American Society of Mammalogists.

For more information, contact Weaver at lukeweav@umich.edu and Wilson Mantilla at gpwilson@uw.edu.

Many animals have tusks, from elephants to walruses to hyraxes. But one thing today’s tusked animals have in common is that they’re all mammals — no known fish, reptiles or birds have them. But that was not always the case. In a published Oct. 27 in the Proceedings of the Royal Society B, a team of paleontologists at Harvard University, the Field Museum, the 91̽�� and Idaho State University traced the first tusks back to ancient mammal relatives that lived before the dinosaurs.

“Tusks are this very famous anatomy, but until I started working on this study, I never really thought about how tusks are restricted to mammals,” said lead author , a postdoctoral researcher at Harvard University and a 91̽��doctoral alum.

“We were able to show that the first tusks belonged to animals that came before modern mammals, called dicynodonts,” said co-author , a curator at the Field Museum in Chicago. “Despite being extremely weird animals, there are some things about dicynodonts — like the evolution of tusks — that inform us about the mammals around us today.”

Dicynodonts lived from about 270 to 201 million years ago, largely before the so-called “time of the dinosaurs.” They ranged from rat- to elephant-sized. Modern mammals are their closest living relatives, but they looked more reptilian, with turtle-like beaks. One of their defining features is a pair of protruding tusks in their upper jaws. The word dicynodont means “two canine teeth.”

Not all protruding teeth are tusks. Their composition and growth patterns reveal whether they count.

“For this paper, we had to define a tusk, because it’s a surprisingly ambiguous term,” said Whitney.

For a tooth to be a tusk, the researchers argued it must extend out past the mouth, keep growing throughout the animal’s life and, unlike most mammals’ teeth — including ours — tusks’ surfaces are made of dentine rather than hard enamel.

Under these parameters, elephants, walruses, warthogs and hyraxes have tusks. Other big teeth in the animal kingdom don’t make the cut, though. For instance, rodent teeth, even though they sometimes stick out and are ever-growing, have an enamel band on the front of the tooth, so they don’t count.

Some of the dicynodont tusks that the team observed in Zambia didn’t fit the definition of a tusk either: They were coated in enamel instead of dentine.

The different makeup of teeth versus tusks gives scientists insights into an animal’s life.

“Enamel-coated teeth are a different evolutionary strategy than dentine-coated tusks,” said Whitney. “It’s a trade-off.”

Enamel teeth are tougher than dentine. But because of the geometry of how teeth grow in the jaw, if you want teeth that keep growing throughout your life, you can’t have a complete enamel covering.

Animals like humans made an evolutionary investment in durable but hard-to-fix teeth — once our adult teeth grow in, we’re out of luck if they get broken. Tusks are less durable, but they grow continuously, even if they get damaged. It’s like the compromise of getting a car that’s very reliable but very difficult to get repaired, versus driving a beater that needs frequent repairs but is cheap and easy to fix.

The different kinds of teeth animals have evolved tell scientists about the pressures those animals faced that could have produced those teeth. Animals with tusks might use them for fighting or for rooting in the ground, exposing them to little injuries that would be risky for enamel teeth that don’t grow continuously.

To study whether dicynodonts tusks really were tusks, the researchers cut paper-thin slices out of the fossilized teeth of 19 dicynodont specimens, representing ten different species, and examined their structure under a microscope. They also used micro-CT scans to examine how the teeth were attached to the skull, and whether their roots showed evidence of continuous growth.

The scientists found that some dicynodont teeth are indeed tusks, while others, particularly those of some of the earlier species, were just large teeth. It wasn’t a strict progression from non-tusks to tusks, though — different members of the dicynodont family evolved tusks independently.

They also discovered some adaptations that dicynodonts needed to evolve true tusks, including flexible ligament attachments between tooth and jaw and reduced rates of tooth replacement, according to Angielczyk.

The study, which shows the earliest known instance of true tusks, could help scientists better understand evolutionary processes.

“Tusks have evolved a number of times, which makes you wonder how — and why? We now have good data on the anatomical changes that needed to happen for dicynodonts to evolve tusks,” said co-author , a 91̽��professor of biology and a curator at the UW’s Burke Museum of Natural History & Culture. “For other groups, like warthogs or walruses, the jury is still out.”

Most of the dicynodont fossils analyzed in the study were collected during fieldwork in Tanzania and Zambia. These specimens, which are currently stored at the Burke Museum and other U.S. museums, will be repatriated at the end of the project and become part of the permanent collections at the National Museum of Tanzania and the Livingstone Museum in Zambia. This partnership allows for researchers across the globe to study the fossils, and ultimately bring the specimens back to their home nations for further research.

Future studies could examine other dicynodont species and how their tusks — or non-tusks — developed. Sidor’s lab at 91̽��is one of a handful across the country where the fossilized bones and teeth are routinely analyzed at the microscopic scale.

“Thin-sectioning can also provide a lot of useful information, because bones and teeth can capture a record of an animal’s life in their tissues,” said Sidor. “On a tusk that’s ever-growing, the dentine records a daily measure of how fast the animal was growing. Did it grow faster or slower over certain seasons? Stop growing for a certain period of time? Creating thin sections of bones and teeth opens up a lot of other interesting things about the animal almost like analyzing tree rings. These are the types of questions we can continue to research.”

Co-author is 91̽��doctoral alum , an assistant professor at Idaho State University and assistant curator of vertebrate paleontology at the Idaho Museum of Natural History. The research was funded by the National Science Foundation and National Geographic.

Adapted from a release by the Field Museum and Harvard University.

A team of paleontologists from the 91̽�� and its excavated four dinosaurs in northeastern Montana this summer. All fossils will be brought back to the Burke Museum where the public can watch paleontologists remove the surrounding rock in the .

The four dinosaur fossils are: the ilium — or hip bones — of an ostrich-sized theropod, the group of meat-eating, two-legged dinosaurs that includes Tyrannosaurus rex and raptors; the hips and legs of a duck-billed dinosaur; a pelvis, toe claw and limbs from another theropod that could be a rare ostrich-mimic Anzu, or possibly a new species; and a Triceratops specimen consisting of its skull and other fossilized bones. Three of the four dinosaurs were all found in close proximity on Bureau of Land Management land that is currently leased to a rancher.

In July 2021, a team of volunteers, paleontology staff, K-12 educators who were part of the and students from 91̽��and other universities worked together to excavate these dinosaurs. The fossils were found in the , a geologic formation that dates from the latest portion of Cretaceous Period, 66 to 68 million years ago. Typical paleontological digs involve excavating one known fossil. However, the Hell Creek Project is an ongoing research collaboration of paleontologists from around the world studying life right before, during and after the that killed off all dinosaurs except birds. The Hell Creek Project is unique in that it is sampling all plant and animal life found throughout the rock formation in an unbiased manner.

“Each fossil that we collect helps us sharpen our views of the last dinosaur-dominated ecosystems and the first mammal-dominated ecosystems,” said , a 91̽��professor of biology and curator of vertebrate paleontology at the Burke Museum. “With these, we can better understand the processes involved in the loss and origination of biodiversity and the fragility, collapse and assembly of ecosystems.”

All of the dinosaurs except the Triceratops will be prepared in the Burke Museum’s fossil preparation laboratory this fall and winter. The Triceratops fossil remains on the site because the dig team continued to find more and more bones while excavating and needs an additional field season to excavate any further bones that may be connected to the surrounding rock. The team plans to finish excavation in the summer of 2022.

Called the “Flyby Trike” in honor of the rancher who first identified the dinosaur while he was flying his airplane over his ranch, the team has uncovered this dinosaur’s frill, horn bones, individual rib bones, lower jaw, teeth and the occipital condyle bone — nicknamed the “trailer hitch,” which is the ball on the back of the skull that connects to the neck vertebrae. The team estimates approximately 30% of this individual’s skull bones have been found to date, with more potential bones to be excavated next year.

The Flyby Trike was found in hardened mud, with the bones scattered on top of each other in ways that are different from the way the bones would be laid out in a living animal. These clues indicate the dinosaur likely died on a flood plain and then got mixed together after its death by being moved around by a flood or river system, or possibly moved around by a scavenger like a T. rex, before fossilizing. In addition, the Flyby Trike is one of the last Triceratops living before the K-Pg mass extinction. Burke paleontologists estimate it lived less than 300,000 years before the event.

“Previous to this year’s excavations, a portion of the Flyby Trike frill and a brow horn were collected and subsequently prepared by volunteer preparators in the fossil preparation lab. The frill was collected in many pieces and puzzled together fantastically by volunteers. Upon puzzling the frill portion together, it was discovered that the specimen is likely an older ‘grandparent’ Triceratops,” said Kelsie Abrams, the Burke Museum’s paleontology preparation laboratory manager who also participated in this summer’s field work. “The triangular bones along the frill, called ‘epi occipitals,’ are completely fused and almost unrecognizable on the specimen, as compared to the sharp, noticeable triangular shape seen in younger individuals. In addition, the brow horn curves downwards as opposed to upwards, and this feature has been reported to be seen in older animals as well.”

Amber and seed pods were also found with the Flyby Trike. These finds allow paleobotanists to determine what plants were living alongside Triceratops, what the dinosaurs may have eaten, and what the overall ecosystem was like in Hell Creek leading up to the mass extinction event.

“Plant fossil remains from this time period are crucial for our understanding of the wider ecosystem. Not only can plant material tell us what these dinosaurs were perhaps eating, but plants can more broadly tell us what their environment looked like,” said Paige Wilson, a 91̽��graduate student in Earth and space sciences. “Plants are the base of the food chain and a crucial part of the fossil record. It’s exciting to see this new material found so close to vertebrate fossils!”

Museum visitors can now see paleontologists remove rock from the first of the four dinosaurs — the theropod hips — in the Burke’s paleontology preparation laboratory. Additional fossils will be prepared in the upcoming weeks. All four dinosaurs will be held in trust for the public on behalf of the Bureau of Land Management and become a part of the Burke Museum’s collections.

For high resolution images, videos and interviews, contact burkepr@uw.edu.

A new published Feb. 24 in the journal Royal Society Open Science documents the earliest-known fossil evidence of primates.

A team of 10 researchers from across the U.S. analyzed several fossils of Purgatorius, the oldest genus in a group of the earliest-known primates called plesiadapiforms. These ancient mammals were small-bodied and ate specialized diets of insects and fruits that varied by species. These newly described specimens are central to understanding primate ancestry and paint a picture of how life on land recovered after the Cretaceous-Paleogene extinction event 66 million years ago that wiped out all dinosaurs — except for birds — and led to the rise of mammals.

, a 91̽�� professor of biology and curator of vertebrate paleontology at the UW’s , co-led the study with of Brooklyn College and the City University of New York. The team analyzed fossilized teeth found in the Hell Creek area of northeastern Montana. The fossils, which are now part of the collections at the University of California Museum of Paleontology, are estimated to be 65.9 million years old, about 105,000 to 139,000 years after the mass extinction event. Based on the age of the fossils, the team estimates that the ancestor of all primates —including plesiadapiforms and today’s primates such as lemurs, monkeys and apes — likely emerged by the Late Cretaceous and lived alongside large dinosaurs.

“It’s mind blowing to think of our earliest archaic primate ancestors,” said Wilson Mantilla. “They were some of the first mammals to diversify in this new post-mass extinction world, taking advantage of the fruits and insects up in the forest canopy.”

The fossils include two species of Purgatorius: Purgatorius janisae and a new species described by the team named Purgatorius mckeeveri. Three of the teeth found have distinct features compared to any previously known Purgatorius species and led to the description of the new species.

Purgatorius mckeeveri is named after Frank McKeever, who was among the first residents of the area where the fossils were discovered, and also the family of John and Cathy McKeever, who have since supported the field work where the oldest specimen of this new species was discovered.

“This was a really cool study to be a part of, particularly because it provides further evidence that the earliest primates originated before the extinction of non-avian dinosaurs,” said co-author Brody Hovatter, a 91̽��graduate student in Earth and space sciences. “They became highly abundant within a million years after that extinction.”

“This discovery is exciting because it represents the oldest dated occurrence of archaic primates in the fossil record,” said Chester. “It adds to our understanding of how the earliest primates separated themselves from their competitors following the demise of the dinosaurs.”

Co-author on the study was the late who was a professor emeritus at the University of California, Berkeley and former director of the UC Museum of Paleontology. Additional co-authors are Jason Moore and Wade Mans of the University of New Mexico; Courtney Sprain of the University of Florida; William Mitchell of Minnesota IT Services; Roland Mundil of the Berkeley Geochronology Center; and Paul Renne of UC Berkeley and the Berkeley Geochronology Center. The research was funded by the National Science Foundation, the UC Museum of Paleontology, the Myhrvold and Havranek Charitable Family Fund, the UW, the CUNY and the Leakey Foundation.

For high resolution images and interviews, contact burkepr@uw.edu.

A new study led by paleontologists at the 91̽�� and its indicates that the earliest evidence of mammal social behavior goes back to the Age of Dinosaurs.

The evidence, Nov. 2 in the journal Nature Ecology & Evolution, lies in the fossil record of a new genus of — a small, rodent-like mammal that lived during the Late Cretaceous of the dinosaur era — called Filikomys primaevus, which translates to “youthful, friendly mouse.” The fossils are the most complete mammal fossils ever found from the Mesozoic in North America. They indicate that F. primaevus engaged in multi-generational, group-nesting and burrowing behavior, and possibly lived in colonies. Study co-authors — including lead author , a 91̽��graduate student in biology, and senior author , a 91̽��professor of biology and curator of vertebrate paleontology at the Burke Museum — analyzed several fossils, all about 75.5 millioin years old, and extracted from a well-known dinosaur nesting site called Egg Mountain in western Montana.

Fossil skulls and skeletons of at least 22 individuals of F. primaevus were discovered at Egg Mountain, typically clustered together in groups of two to five, with at least 13 individuals found within a 30 square-meter area in the same rock layer. Based on how well preserved the fossils are, the type of rock they’re preserved in, and F. primaevus’ powerful shoulders and elbows — which are similar to today’s living burrowing animals — Weaver, Wilson Mantilla and co-authors hypothesize these animals lived in burrows and were nesting together. Furthermore, the animals found were a mixture of multiple mature adults and young adults, suggesting these were truly social groups as opposed to just parents raising their young.

“It was crazy finishing up this paper right as the stay-at-home orders were going into effect — here we all are trying our best to socially distance and isolate, and I’m writing about how mammals were socially interacting way back when dinosaurs were still roaming the Earth!” said Weaver. “It is really powerful, I think, to see just how deeply rooted social interactions are in mammals. Because humans are such social animals, we tend to think that sociality is somehow unique to us, or at least to our close evolutionary relatives, but now we can see that social behavior goes way further back in the mammalian family tree. Multituberculates are one of the most ancient mammal groups, and they’ve been extinct for 35 million years, yet in the Late Cretaceous they were apparently interacting in groups similar to what you would see in modern-day ground squirrels.”

Previously, scientists thought social behavior in mammals first emerged after the mass extinction that killed off the dinosaurs, and mostly in the Placentalia — the group of mammals humans belong to, which all carry the fetus in the mother’s uterus until a late stage of development. But these fossils show mammals were socializing during the Age of Dinosaurs, and in an entirely different and more ancient group of mammals — the multituberculates.

“These fossils are game changers,” said Wilson Mantilla. “As paleontologists working to reconstruct the biology of mammals from this time period, we’re usually stuck staring at individual teeth and maybe a jaw that rolled down a river, but here we have multiple, near complete skulls and skeletons preserved in the exact place where the animals lived. We can now credibly look at how mammals really interacted with dinosaurs and other animals that lived at this time.”

Co-authors are and at Montana State Univeristy, at Yale University and Meng Chen of Nanjing University. The research was funded by the National Science Foundation, Doris O. and Samuel P. Welles Research Fund, the 91̽��and the Burke Museum.

For high resolution images and interviews, contact burkepr@uw.edu.

Reference: “” by Whitney MR and Sidor CA. Communications Biology. DOI: 10.1038/s42003-020-01207-6

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Major findings

We provide evidence for a hibernation-like condition in Lystrosaurus, a mammal relative that lived in the Antarctic portion of Pangea about 250 million years ago. This discovery was enabled by high-resolution of incremental growth marks preserved in the tusks of Lystrosaurus.

Frequently Asked Questions

What is Lystrosaurus?

• is a type of , a major group of primarily herbivorous vertebrates that were common during the Permian and Triassic periods. Dicynodonts are characterized by their turtle-like beaks and ever-growing tusks, which are present in most species. They are distantly related to modern mammals.
• Lystrosaurus is known from rocks from about 253-248 million years ago and ranged from about the size of a corgi to slightly smaller than a cow.
• Fossils of Lystrosaurus are known from China, Russia, India, South Africa and Antarctica and this geographic distribution was one of the early pieces of evidence used in support of a large supercontinent called Pangea.
• Fossils of Lystrosaurus have been found in burrow structures in South Africa and similar burrow trace fossils have been recovered from Antarctica, but not with Lystrosaurus inside them.

What is torpor?

• is a term that refers to the general pattern of vertebrate physiology where there are periodic reductions in metabolic activity. These periods of slower metabolism are often related to seasonal changes in the environment that create unfavorable conditions.
• Hibernation is one form of torpor and is found in warm-blooded animals today. Hibernation is marked by reduction of metabolic activity with periodic small reactivations of activity throughout the hibernation period. This is in contrast to a different kind of torpor called brumation which is common in cold-blooded animals. In brumation, metabolic activity is completely inactive for the entirety of the torpor period.
• Modern examples of hibernators include many North American bear, echidnas, many rodents, hedgehogs, badgers and some lemurs during dry seasons. Modern examples of daily torpor, a form of torpor characterized by daily reductions in metabolic activity, include many birds and bats, as well as bushbabies. Modern examples of brumation include many reptiles such as lizards, turtles and snakes.

What was Antarctica like in the Early Triassic?

• In general, the Early Triassic (252-247 million years ago) was a warm period in Earth history.
• The climate of Antarctica during the Early Triassic is still a subject of active research, but it is clear that the continent was NOT under a thick ice sheet like today. The discovery of fossil plants — including fossil forests — as well as a wide variety of land-living vertebrate fossils demonstrate that the continent was habitable for at least part of the year.

What is thin-sectioning?

• We make thin-sections of fossil bones and teeth so that we could study the fine, inner details that are preserved in these hard tissues. These small, microscopic details act as storybooks, preserving a lot of information about the biology of these animals while they were alive. As is easy to imagine, studying the biology of animals that lived millions of years ago can be challenging. These details, in this case the tree-ring-like growth marks, preserve critical clues into the biology of fossilized animals.

How did you analyze the tusks?

• The way that these tusks grow is layer by layer, growing inward toward the pulp cavity.
• Growth of the tusk happens periodically during both normal and stressful times for the animal. Each increment of growth will leave behind a ring. We looked at both normal growth mark rings and growth marks that were especially thick, which represent a stressful time for the animal.
• We counted how much growth had occurred between rings, and also measured the thickness of the stressful rings.
• We compared periods of regular growth and stress in polar Antarctic tusks to those from non-polar South African localities from the same time period.

Has torpor been found in the fossil record before?

• Torpor has been reported in some fossil rodents, where hibernation marks were found in their ever-growing incisors. But these relatively recent fossils are from the Pleistocene, on the order of hundreds of thousands of years old.
• Our study is by far the oldest evidence of torpor.
• Given how widespread torpor is in modern vertebrates, it is expected that this is not a trait that evolved recently, and instead has likely been widespread throughout the vertebrate evolutionary history. However, torpor is a difficult feature to study in the fossil record.
• This study provided a unique opportunity to study torpor in the fossil record. First, Lystrosaurus had ever-growing tusks, which provide a lengthy record of regular and stress growth rings. Second, we have two populations to compare, a polar population from Antarctica and a non-polar population from South Africa.
• This study suggests torpor was present even 250 million years ago and lends support for the idea that having a flexible physiology may serve as a key feature in surviving mass extinctions.

What this paper does NOT say:

• This paper does not say that Lystrosaurus was a reptile — or a dinosaur! Though it is only a distant relative to mammals, Lystrosaurus is actually more closely related to mammals, including humans, than to any reptile. Lystrosaurus is a member of a very early branch on the lineage that eventually gave rise to mammals.
• This paper does not say that Lystrosaurus was the only animal experiencing torpor in the Early Triassic. This is the first study of its kind. There is a rich assemblage of vertebrates from the Early Triassic of Antarctica and similar studies on their seasonal physiologies have not yet been launched.
• This paper does not prove that Lystrosaurus was hibernating. This is a preliminary study that puts forward a hypothesis. Our hope is that there is continued testing of this hypothesis and additional sampling of Lystrosaurus and other polar vertebrates to look for signals of hibernation or other forms of torpor.

For additional information, contact Christian Sidor at casidor@uw.edu and Megan Whitney at meganwhitney@fas.harvard.edu. 91̽�� press release here.

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

According to new research, this type of adaptation has a long history. In a published Aug. 27 in the journal Communications Biology, scientists at the 91̽�� and its report evidence of a hibernation-like state in an animal that lived in Antarctica during the Early Triassic, some 250 million years ago.

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

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

“Animals that live at or near the poles have always had to cope with the more extreme environments present there,” said lead author , a postdoctoral researcher at Harvard University who conducted this study as a 91̽��doctoral student in biology. “These preliminary findings indicate that entering into a hibernation-like state is not a relatively new type of adaptation. It is an ancient one.”

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

“The fact that Lystrosaurus survived the end-Permian mass extinction and had such a wide range in the early Triassic has made them a very well-studied group of animals for understanding survival and adaptation,” said co-author , a 91̽��professor of biology and curator of vertebrate paleontology at the Burke Museum.

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

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

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

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

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

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

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

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

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

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

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

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

The research was funded by the National Science Foundation.

For more information, contact Sidor at casidor@uw.edu and Whitney at meganwhitney@fas.harvard.edu.

: “Evidence of torpor in the tusks of Lystrosaurus from the Early Triassic of Antarctica” by Whitney MR and Sidor CA.

DOI: 10.1038/s42003-020-01207-6

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Drop-in Session: Cultivating Gratitude in Challenging Time

June 22, 6:00 – 7:00 PM | Zoom

Noticing what we are grateful for and cultivating practices of gratitude can ease anxiety and increase our feelings of connection. This session, hosted by Becca Calhoun, MPH,��will include a guided gratitude meditation, a discussion of the benefits of gratitude and an introduction of several gratitude practices that can be used throughout our daily lives.

Free��|

Henry Art Gallery Viewpoints: A Dialogue Between Jean-François Millet and Jeanne Dunning

Live until June 28 |

Viewpoints��is a rotating series that highlights works from the Henry’s��, paired with commentary and insights from 91̽�� faculty.

This iteration features representations of women and domestic labor in nineteenth-century prints by Jean-François Millet (France, 1814-1875) and the video��Icing��(1996) by Jeanne Dunning (U.S., born 1960). Faculty contributions include professors Juliet McMains in the Department of Dance, and Priti Ramamurthy in the Department of Gender, Women, and Sexuality Studies. Visit the before it closes on Sunday, June 28th.

#BurkeFromHome Trivia Night

Every Friday, 7:00 PM��|��Virtual Event

Join the Burke Museum online on Fridays at 7 PM for #BurkeFromHome Trivia. The popular Burke Trivia Night is back—this time online to practice social distancing while having loads of fun! Get your nerd on with natural history and culture-themed trivia.

BYOB, snacks, and slippers!

Free, please register for access��|

Meany Center – Grupo Corpo Strike Timelapse

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Have you wondered what the work looks like in setting the stage for Meany performances? Check out this timelapse from April when the Grupo Corpo tech team and Meany Center Tech team took out and loaded the truck so Grupo Corpo could do to their next venue.

The Ellison Center’s Podcast Archive

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Did you know the The Ellison Center for Russian, East European and Central Asian Studies�� has an archive of podcasts covering interviews and lectures over the last several years? The center’s goal is to promote in-depth interdisciplinary study of all major post-communist subregions – Eastern and Central Europe, the Baltic region, the Caucasus and Central Asia, and Russia – in order to understand the legacies of the imperial and communist past as well as to analyze the emerging institutions and identities that will shape Eurasia’s future.

Podcast: The Hell Creek and Back; The Story of the Tufts-Love T. rex

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A world of blistering heat and dirt, a biosphere where 20-foot-tall dinosaurs roamed. Home to cretaceous creatures that could rip apart their prey with 6-inch serrated teeth! Venture into this landscape to learn how a group of researchers and school teachers tracked down the elusive Tyrannosaurus Rex in the sweltering badlands on Montana.�� Follow how the last-minute discovery of a small protrusion of ribs led to the extraction of the savage toothed king! You’ll be on the ground in an active paleontological field research site examining fossils from millions of years ago. You’ll even discover out what it takes to bring a prized scientific discovery into the forefront of research.

Looking for more?

Check out UWAA’s Stronger Together web page for��more digital engagement opportunities.

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.