Kent Hups, a high school science teacher in Colorado, discovered a 23-foot trackway of fossilized dinosaur footprints, which offer a glimpse of how the apex predator moved 66 million years ago.
Paleontologists have identified the first confirmed remains of Diplodocus — "Dippy," for short — outside the western U.S., revealing that the iconic long-necked dinosaur reached what is now Spain roughly 150 million years ago.
The findings show that the enormous sauropod didn't live only in North America, as was long thought. Instead, it may have rambled across a land bridge all the way to Europe, the new study suggests.
The discovery, made at the La Tejería site near the small village of El Castellar in eastern Spain, provides some of the strongest fossil evidence yet that dinosaurs could move between North America and Europe during the Late Jurassic, when the Atlantic Ocean was still in its early stages of opening after the breakup of the supercontinent Pangaea. The researchers published their findings Tuesday (Sept. 15) in the Journal of Vertebrate Paleontology.
"Paleontological studies like this one help us better understand the history of life on Earth, reconstruct ancient ecosystems, and understand how they changed through time," study first author Sergio Sánchez Fenollosa, a doctoral student who studies biodiversity and evolutionary biology at the Joint Paleontology Foundation Teruel-Dinópolis (Dinópolis Foundation), a paleontological research institution, told Live Science via email.
A sauropod in Spain
Dippy is one of the best-known dinosaurs. After its fossils made their grand debut at the Carnegie Museum of Natural History in Pittsburgh in the early 1900s, life-size fossil replicas of the towering herbivore were sent around the world, including to England, France, Spain, Argentina and Russia.
But until now, Diplodocus' Late Jurassicfossils were known only from the Morrison Formation in the western United States — and the latest discovery shows that Dippy wasn't a homebody.
The newly unearthed Diplodocus specimen consists of 14 well-preserved tail vertebrae and several chevrons — bones that helped support blood vessels and muscles within the dinosaur's tail.
Study co-author and managing director of the Dinópolis Foundation, Alberto Cobos, said it was a friend who "thought he had spotted some bones on a mountainside," Cobos told Live Science via email. "That very day, I went to the site near El Castellar (a village in the province of Teruel). Sure enough, we saw a couple of sauropod vertebral centers."
Although only part of the skeleton has been recovered, the bones show a series of characteristics associated with Diplodocus, including large cavities corresponding to where air sacs would have been, along with deep grooves running alongside the underside of the tailbones.
The 14 vertebrate and several chevrons found in Spain correspond to the Dipolodocus' anatomy. (Image credit: Carmelo López)
"It was an exciting and continuous process of seeing the pieces of the puzzle gradually fall into place," Sánchez Fenollosa said in a statement. "From the early stages of the osteological study, we noticed strong similarities with several diplodocine sauropods … With each new result, the picture became clearer: we were looking at a Diplodocus."
It's unclear which species of Diplodocus the new specimen is, but like others of its genus, it was a huge dinosaur with an extremely long neck and whip-like tail.
"The Diplodocus from El Castellar was approximately 25 meters [82 feet] long (comparable in size to its North American relatives), making it another of the giant sauropods of the Spanish Jurassic," Cobos said in the statement.
An ancient bridge
Between 195 million and 170 million years ago, the supercontinent Pangaea broke apart as the Atlantic Ocean opened. But the ocean was much narrower than it is today, and the continents were not necessarily as isolated as their modern geography is now.
Evidence indicates that temporary land bridges may have allowed some animals to move between the two regions. The most famous prehistoric land bridge is the Bering Land Bridge that humans used to move between Asia and what is now Alaska. Previous research showed the Bering Land Bridge also existed around 68 million years ago, and it may have allowed an Asian ancestor of Tyrannosaurus rex to trek into North America.
Geological conditions may have allowed dinosaurs like Diplodocus to move between continents, Sánchez Fenollosa told Live Science in an email. "This interpretation is supported not only by the fossil record but also by geological evidence," he said.
The newfound Diplodocus fossils also suggest that the distribution of giant sauropods was more complicated than the fossil record previously indicated.
"More complete specimens will be essential to understand this story in greater detail, particularly to determine which Diplodocus species inhabited Europe: whether it was one already known from North America or a previously unknown species," Sánchez Fenollosa said. "This discovery reminds us that even for such iconic dinosaurs, there are still many unanswered questions about their evolutionary history and biogeography."
Diplodocus is a famous genus of giant sauropod dinosaurs with small heads and long, whip-like tails that lived in the Late Jurassic period (155 to 145 million years ago). Since its discovery in 1878, all confirmed Diplodocus remains have been unearthed from the Morrison Formation fossil hotspot in the western United States. Now, however, paleontologists have identified Diplodocus remains in Spain.
The remains came to light in the El Castellar municipality of the Spanish city of Teruel, and represent the first evidence of Diplodocus beyond the borders of North America. They consist of 14 well-preserved tail vertebrae and several chevron bones (bony arches in the tail). Through traditional anatomical comparisons and advanced phylogenetic analyses, the researchers confidently categorized them as Diplodocus and a close cousin of Diplodocus hallorum.
“As we looked more closely at the anatomy, we began to identify a combination of features characteristic of Diplodocus species. Then, as we carried out different evolutionary analyses, they kept pointing in the same direction,” Sergio Sánchez Fenollosa, lead author of the Journal of Vertebrate Paleontology study and a graduate student in biodiversity and evolutionary biology at the Joint Paleontology Foundation Teruel-Dinópolis research foundation, said in a statement. “With each new result, the picture became clearer: we were looking at a Diplodocus.” Dinópolis is a huge paleontological museum and theme park in Teruel, about 200 miles east of Madrid.
This particular individual dates back to around 150 million years ago. Its place of death indicates that during the Late Jurassic, dinosaurs could migrate from between North America and Europe, probably making use of temporary land bridges that sometimes emerged in the proto-North Atlantic Ocean. During the Jurassic (201.4 to 145 million years ago), the ancient supercontinent Pangea started pulling apart into the Laurasia and Gondwana landmasses, and the Atlantic Ocean also started forming.
Diplodocus are a subgroup of sauropods, which were among the longest land animals to ever walk the Earth. The recent finding sheds light on Iberian Mesozoic (252 to 66 million years ago) ecosystems and sauropod dinosaur diversity in the European Jurassic, Fenollosa explained.
“The Diplodocus from El Castellar was approximately 25 meters long [82 feet] (comparable in size to its North American relatives), making it another of the giant sauropods of the Spanish Jurassic,” said Alberto Cobos, co-author of the study and managing director of the Joint Paleontology Foundation Teruel-Dinópolis. Its remains are now on display at the Aragones Museum of Paleontology at Dinópolis.
The family has put together the Big Premise (a solar flare has flung Oak Street back to the Mesozoic era). The dad predicts, “God's not gonna let us die here.”
In 2016, paleontologist David DeMar Jr. was crawling across a rocky outcrop in northeastern Montana, hunting for fish fossils, when he spotted a dark, reddish-brown nodule about half the size of a golf ball. He picked it up and looked at it through his hand lens. On its surface was something he didn’t expect: a […]
Tyrannosaurus rex fossils are relatively common finds, with dozens of variously complete examples on display in museums around the world. But T. rextracks? That’s an entirely different story. Even when stomped into the mud by a 17,500-pound apex predator, dinosaur footprints rarely last long enough to fossilize over millions of years.
That’s what makes a recent discovery in southwestern North Dakota so remarkable. Paleontologists from the Denver Museum of Nature & Science and Liverpool John Moores University in England have documented not one, but four footprints preserved along a 23-foot-long path within the famous Hell Creek Formation. The prints are the first known trackway made by an adult T. rex, and are described in a study recently published in the Journal of Vertebrate Paleontology.
The tracks were discovered in North Dakota’s Hell Creek Formation: Tyler Lyson
While rare, T. rex footprints are distinctive for their massive size and narrow toes. In this case, each dino-stomp measures about three feet long. Paleontologists identified the roughly 66.5-million-year-old path last year on federal land near the town of Marmath, North Dakota, near the state’s southwestern border with Montana. After carefully clearing the surroundings, researchers imaged each footprint using a high-resolution 3D surface scanner. This allowed the team to digitally analyze the scene, as well as create physical reproductions.
The two left and right imprints suggest that the dinosaur was a sizable adult with an estimated 13-foot stride—but paleontologists don’t think this particular T. rex was in much of a hurry. Based on the gait, it was likely moseying around at 3.5 to 4.5 miles per hour, or about the same speed as a human going on a power-walk. Given the tracks’ weathering and erosion, the team stresses their theorized speed is somewhat speculative.
3D scans allowed researchers to generate digital recreations as well as physical models. Credit: Antoine Bercovici
Paleontologists are now planning to excavate three of the four footprints later this year, then transfer them by helicopter to the Denver Museum of Nature & Science.
“Bones tell us an enormous amount about these animals, but footprints capture a moment of behavior. With a trackway, we can actually follow an animal as it moved across the landscape,” Tyler Lyson, a Denver Museum of Nature & Science paleontologist and study co-author, said in a statement. “That is incredibly rare for T. rex.”
Before 2025, paleontologists had confirmed exactly two footprints anywhere in the world made by an adult Tyrannosaurus rex — one in New Mexico, one in Montana. Isolated prints, each capturing a single instant, with no way to tell how the animal that made them actually moved. That changed with a discovery in the badlands of […]
An AI summarizes the Young Earth Creationist (YEC) perspective in that dinosaurs were created on Day 6 of creation alongside Adam, and therefore were on Noah's Ark. The biblical interpretation of creatures like Behemoth and Leviathan and dragon is what we now call dinosaurs though the word "dinosaur" is not found in the Bible.
The largest Tyrannosaurus rex fossils ever discovered belong to a 66-million-year-old apex predator named Scotty. Like many T. rex skeletons, it’s difficult to determine if the specimen was male or female, but Scotty was an unequivocal bruiser. Standing 13-feet-tall at the hip and measuring upwards of 43-feet-long, the Late Cretaceous hunter weighed as much as 19,500 pounds.
However, Scotty isn’t simply the biggest T. rex on record. One of its bones still has traces of preserved soft tissue. This is almost never seen in paleontology, as soft tissues degrade due to the ravages of time. The only way to safely examine these delicate remains is through highly sensitive techniques like neutron imaging. But with the help of researchers at the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) in Tennessee, paleontologists recently glimpsed Scotty’s rib and its remaining tissue in unprecedented detail. The results offer some of the first in-depth looks at fossilized dinosaur tissue on a microscopic level.
“It’s like winning the lottery,” Mauricio Barbi, a physicist at the University of Regina (U of R) in Saskatchewan, Canada, said in a recent interview. “Scotty’s rib contains a vast network of mineralized blood vessels that has never before been observed in a fossil.”
The reason for the blood vessels’ preservation is also a window into the T. rex’s death. The broken rib indicates that Scotty likely succumbed to injuries sustained during a dinosaur brawl. After the rib cracked, iron-saturated blood covered the wound and formed tiny blood vessels to facilitate faster healing. The anatomical response wasn’t enough, and Scotty soon died in a salty marsh. The surrounding environment slowed down the T. rex’s decomposition so much that it allowed many of those blood vessels to fossilize.
To get a closer look at these details, paleontologists relied on neutron imaging to see the lighter elements present in the fossils as well as X-ray imaging to look at the heavier ones. From there, researchers also used synchrotron radiation and other microscopy approaches to analyze the healing tissues on a cellular level. Importantly, all of this imaging was possible without damaging Scotty’s priceless fossils.
“Neutrons not only corroborated what we found with synchrotron radiation techniques that led to the discovery of blood vessels in Scotty’s rib,” explained U of R physicist Marcella Berg. “They also proved to be a highly valuable addition to our current studies in search of soft tissue preservation in fossils.”
For decades, paleontologists have used the presence of stones inside the skeletons of dinosaurs as an indicator that the animal was herbivorous. These stones, known as gastroliths, have been found in numerous species and were assumed to serve to grind plant material in the stomach, just like many birds do today. However, this relationship has […]
Analysis of living vertebrates shows that changes in brain evolution helped drive major shifts in reproduction across dinosaurs and birds. A bird egg can look surprisingly oversized for the body that produced it. That puzzle becomes even stranger when viewed through deep time: the largest known bird eggs exceed the largest eggs found from nonavian [...]
When the famous Chicxulub asteroid struck what is now Mexico's Yucatán Peninsula 66 million years ago, it ended the reign of the nonavian dinosaurs. As ecosystems recovered, small, adaptable mammals rapidly spread into newly vacant niches, evolving new diets, larger bodies and more diverse ways of life until they dominated the land within a few million years.
Now, new evidence suggests that even before the asteroid hit, Earth was already beginning to rot.
A study published May 12 in the journal PNAS found evidence of environmental fungal blooms beforeand after the Cretaceous-Paleogene (K-Pg) mass extinction event. Looking at microscopic fossils from rocks dating to the K-Pg event in North America, a team of researchers led by Dr. Arturo Casadevall, chair of the Molecular Microbiology and Immunology Department at Johns Hopkins University, identified an earlier fungal bloom dating to roughly 30,000 to 100,000 years beforethe asteroid hit, during a period of cooling linked to intense volcanic activity in the Deccan Traps in what is now India.
Not all experts agree that the asteroid-impact led to the rise of mammals due to dinosaurs being more susceptible to fungal infections. (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)
The researchers also found a fungal spike immediately after the Chicxulub impact exactly when dead plants and animals would have littered devastated ecosystems. The finding adds to earlier evidence from New Zealand that suggests the fungal bloom wasn't just a local event.
This idea feeds into a controversial idea called the fungal infection-mammalian selection (FIMS) hypothesis. First proposed two decades ago by Casadevall and subsequently updated in 2018 and 2026 papers, the FIMS hypothesis suggests that the abundance of fungus before the asteroid impact may have helped mammals gain an evolutionary advantage over the dinosaurs that remained after that cataclysm.
The hypothesis doesn't argue that fungus wiped out the dinosaurs. Instead, it proposes that mammals' live births and immune systems may have helped them withstand the rise of fungus in ways egg-laying reptiles and nonavian dinosaurs could not, thereby giving them the upper hand in disrupted ecosystems full of rot, cold, starvation and polluted air.
"The fungal infection mammalian selection hypothesis is focused on how the mammals became the dominant land animals," Casadevall told Live Science via email, "not dinosaur extinction."
But not all experts are convinced. Mary O'Connell, the Chair of the Zoology department at the University of Manchester told Live Science via email that the hypothesis doesn't fit all the evidence and that "it emerges from a chain of plausibility arguments rather than direct evidence, and the links in the chain are weaker than the framing may suggest."
A fungal world before the asteroid
To find this pre-asteroid fungal bloom in their new study, Casadevall and Rosanna Baker, who researches fungus at Johns Hopkins, focused on palynomorphs — tiny fossilized organic remains, including fungal spores, fungal hyphae and plant pollen — preserved in ancient sediment layers from the Denver Basin in Colorado dating back to the K-Pg extinction.
Baker counted between 100 and 500 microfossils per sample across sediment layers spanning about 60,000 years before the K-Pg mass extinction eventto 30,000 years after it. Most samples were dominated by plant material, but some layers contained 50% or more fungal spores. The researchers interpreted this high proportion of fungal spores as a sign of ecological disturbance — more dead material and more fungi feeding on it, especially after the dinosaur-killing asteroid.
Baker and Casadevall also found an earlier fungal bloom dating to roughly 10,000 to 30,000 years before the asteroid impact.
"What surprised us was the proliferation in association with Deccan volcanism, which implies ecological disruption prior to [the] meteor impact," Casadevall told Live Science via email.
In other words, ecosystems may have already been under stress — and faced with a fungal overgrowth — before the asteroid delivered the final blow.
The case for FIMS
When Casadevall first proposed the FIMS hypothesis, it rested on a simple observation: Mammals are unusually resistant to invasive fungal diseases.
Fungi are major pathogens of plants, insects, amphibians and many reptiles, but life-threatening systemic fungal infections are relatively rare in mammals with healthy immune systems. Casadevall argued that mammals' relative resistance to fungi came from their sophisticated immune systems. In mammals, first-line, relatively nonspecific defenses such as neutrophils recognize fungal cell walls, engulf spores and attack invasive filaments, while the adaptive arm of the immune system excels at building customized antibodies that selectively target specific fungi, and then creating immune memory so the invaders are recognized the next time they're encountered.
Casadevall also initially believed that mammals' high, stable body temperatures — generally around 97 to 104 degrees Fahrenheit (36 to 40 degrees Celsius) — could prevent many environmental fungi from growing well enough to establish an infection.
"The success of mammals made no sense given their high energy needs and this idea provided a plausible mechanism for their success," Casadevall said.
The effects of the asteroid would have included increased volcanism and worsening air quality as ash and dust filled the sky. (Image credit: Mark Garlick via Getty Images)
After the asteroid hit, forests burned, plants died, darkness fell and dead matter piled up, providing a feast for fungi. If fungal spores filled the air, surviving animals may have inhaled enormous, possibly dangerous doses.
However, the FIMS hypothesis proposes that mammals had several possible adaptations against these fungal invaders that other animals did not. In addition to having warm body temperatures and complex immune systems, mammals who could maintain stable body temperatures could forage during the cold "impact winter," when ash and dust blocked out the light of the sun. Meanwhile the dinosaurs, who were originally thought to be the "cold-blooded," would have struggled to stay active and find food, leading them to become weaker and more susceptible to disease.
Differences in gestation may have mattered, too. Many mammals protect developing embryos inside the mother's body, where warmth and immunity could shield them from fungi. In contrast, all dinosaurs laid eggs. Those eggs developed in nests, which were often in contact with soil and decaying plant matter — the exact environments where fungi thrive. Modern fungi can invade reptile eggs, and fossilized hyphae, a type of fungus, was described in dinosaur eggshells in a 2008 study.
That does not prove fungi wiped out dinosaur nests. Fossilized hyphae could suggest either that fungi invaded a living egg, or that fungi colonized the egg after death. Still, eggshells provide one clue that fungi were a problem for the survival of dinosaur young..
A sick sauropod
Another potential line of evidence to buttress the FIMS hypothesis came from dinosaur bones that showed evidence of fungal infection.
Sauropods had long, air-filled neck bones connected to their respiratory system. In fossils of healthy sauropods, the places where air-sac tissue met bone are smooth, sometimes glass-like, Woodruff told Live Science.
But in this animal, the normally smooth sockets were rough and irregular. "Coming out of the socket — like imagine coming out towards you —it looked like fossilized heads of broccoli florets," Woodruff said. "And I had never seen that."
Unsure what he was looking at, Woodruff posted a photo online and asked whether anyone had seen anything similar. Other anatomists and paleontologists quickly weighed in. Their response, he recalled, was essentially, "That's exactly what we would have predicted a respiratory infection to look like," he said.
Recent evidence revealed that a sauropod could have suffered from a fungal infection. (Image credit: ROGER HARRIS/SCIENCE PHOTO LIBRARY via Getty Images)
However, the researchers could not identify the exact disease that caused the inflammation. In modern birds, airsacculitis can be caused by fungal infections such as aspergillosis, but also by bacterial infections. Without preserved soft tissue or fungal structures, they stopped short of confirming a fungal infection diagnosis.
Either way, Woodruff thinks the sauropod was probably sick enough that the infection contributed to its death. It may have become too weak to keep up, too ill to eat or drink properly, or too vulnerable to escape predators.
The case against FIMS
Even so, many experts remain skeptical of Casadevall's hypothesis. For one thing, the asteroid and its aftermath already explain a tremendous amount. The impact triggered tsunamis, earthquakes and a global food-web collapse. Those disasters alone would have killed off large dinosaurs at the top of disrupted food chains.
Another problem revolves around body temperature. In 2005, when Casadevall first proposed his hypothesis, dinosaurs were often thought of as "cold-blooded," while mammals were "warm-blooded." But over the years, research has uncovered that many nonavian dinosaurs, such as Velociraptor, T. rex and Brachiosaurus, were likely warm-blooded, too — so body temperature wouldn't explain why fungus would have been a big problem for many dinosaurs.
Complicating the picture, birds — the only surviving dinosaurs — often have higher body temperatures than mammals do. So the FIMS theory rests on an assumption that living examples of dinosaurs don't support, Flynn said.
If everything we know that suggests dinosaurs are more susceptible to fungal infections is based on living dinosaurs (birds) and they survived, doesn't that rather undermine this hypothesis?
Jingmai O'Connor, paleontologist at the Field Museum in Chicago
Around the time of the asteroid impact, cold-blooded creatures like turtles and crocodilians that lived in the water "don't really suffer as severely as other groups, even including mammals," Andrew Flynn, an assistant professor of paleobotany at New Mexico State University, told Live Science. "Clearly this fungal thing is not probably what's causing mammals to rise up and go on to dominate the ecosystem."
The FIMS hypothesis also has a contradiction at its heart, said Jingmai O'Connor, a paleontologist at the Field Museum in Chicago.
"It's just a hypothesis I had vaguely heard about but was not popular, not often mentioned, and I guess I would say 'out of favor,'" O'Connor told Live Science via email. "If everything we know that suggests dinosaurs are more susceptible to fungal infections is based on living dinosaurs (birds) and they survived, doesn't that rather undermine this hypothesis?"
Dr. Isabel Jimenez, an assistant professor at Johns Hopkins University and a proponent of FIMS, agrees that this discrepancy must be explained.
"For the FIMS hypothesis to still hold water, we have to consider alternative mechanisms by which dinosaurs could have been more susceptible to fungal diseases than mammals," Jimenez told Live Science in an email.
Modern-day birds are avian theropods — the surviving branch of the dinosaur family tree — and likely faced the same fungal pressures as their extinct relatives. More recently, in 2026, Jimenez and Casadevall have suggested a tweak to their theory: that some of the small-bodied, beaked, flying or semiflying theropods may have been able to pull through, despite some baseline higher susceptibility to fungal disease. That's because they were small, had feathers to better insulate their bodies, and maintained generalist diets that enabled them to use more food sources than the dinosaur lineages that died out.
Working with Jimenez, Casadevall outlined an updated version of the FIMS hypothesis in a paper published earlier this year. In it, they propose that dinosaurs' respiratory systems may have made them more at risk than their mammalian counterparts.
Whereas mammals breathe by expanding and contracting flexible lungs filled with blood-rich alveoli, modern birds — and probably many dinosaurs — have rigid lungs ventilated by a network of thin-walled air sacs. The air sacs act as bellows, maintaining one-way airflow through the lungs, but they perform little gas exchange and have relatively poor blood supply. This system could have also carried inhaled fungal spores deep into the respiratory tract, where they may have settled in air sacs that are harder for circulating immune cells to reach and clear.
While birds have a similar sophisticated immune system as mammals — including macrophages and antibodies — their air sacs extend throughout the body and sometimes into the bones, making fungal infections easier to spread beyond just the respiratory system.
This possible weakness is what Jimenez and Casadevall suggest is what made air-sac-bearing dinosaurs vulnerable to fungal infections, similar to modern birds.
A diagram of the avian respiratory system, with its many air sacs found around the bird's body (Image credit: Anatoliy Stepura via Getty Images)
After the asteroid strike, there would have been soot and sulfur polluting the air and dinosaurs would have been nutritionally stressed. "So secondary fungal infections are certainly possible," Jimenez said, referring to infections that take root after the body's defenses are weakened.
But skeptics argue that even with these updates in the FIMS hypothesis, more evidence is needed to show it's not just possible but likely.
The idea that their air-sac respiratory systems made them more vulnerable to fungus is "a more testable claim," but its likely impact on dinosaurs would also be more limited, because of competing environmental factors, O'Connell said.
And because only a handful of fungal species actually cause disease in animals, to show that fungi worsened dinosaur deaths, researchers would need to find evidence of elevated fungal disease in dinosaur fossils from right after the asteroid struck, O'Connell said.
"We would also need to be able to identify elevation of pathogenic fungal spores in the sedimentary record at that boundary, rather than just more spores," she said.
Overall, "the fungal infection-mammalian selection hypothesis feels like a conjecture in search of any supporting evidence," paleontologist and science writer Riley Black, told Live Science in an email.
How much do you know about the king of the dinosaurs? Test your knowledge with our T. rex quiz!
The spots on a leopard, the stripes on a zebra, and the mask on a raccoon are all types of coloration in mammal fur, referred to as pelage. Scientists have struggled for a long time to understand how these colorations evolved. A team of researchers recently discovered how to reconstruct the colors of ancient mammal fur using cell structures that contain the chemical pigment melanin, known as melanosomes. They hope to use this understanding of ancient mammal pelage to determine how they lived and what their environments were like.
To decipher the color of ancient mammal fur, the researchers constructed a statistical computer model to predict their fur colors based on the shape of their melanosomes. First, they needed to understand how the shapes of melanosomes control fur color in modern mammals. To measure the length and width of the modern melanosomes, the scientists used a beam of electrons like a flashlight to map them in great detail, a technique called scanning electron microscopy.
They measured the length and width of 2,615 melanosomes from the fur of 116 different living mammal species, including a Red Panda, a German Shepard, and one or more species of most types in the mammalian classification. Then they recorded the wavelengths of light reflected off each melanosome using a microspectrophotometer. These wavelengths represented the exact color of hair from each melanosome they measured. This means they now had a quantitative measurement of the color of each hair to compare with its corresponding melanosome length and width.
When they examined their data, the researchers found that spherical melanosomes produced brighter fur colors, like reds and oranges, while elongated melanosomes produced darker fur colors, like browns and grays. The researchers plotted the microspectrophotometric measurements for each melanosome as a graph showing how much light it absorbed across each possible wavelength, creating reflectance curves. Based on these data, the researchers used computer software to create a statistical model that could predict reflectance curves, and therefore color, from melanosome shape alone.
Once the researchers created a model, they needed to find fossilized mammal melanosomes to predict their fur color. Mammal fossils are rare, and pieces of cells are only preserved in the most immaculate fossil deposits. In fact, these researchers only found 6 fossils of this caliber, from Mesozoic rocks deposited around 250 million years ago, soon after mammals evolved.
The fossils came from 2 world-renowned deposits in Northeastern China, the Yanliao and Jehol biotas. They selected 5 previously studied fossils from these locations, including 1 specimen of Megaconus mammaliaformis, 1 specimen of Vilevolodon diplomylos, 2 specimens from the group Docodonta, and 1 specimen from the group Eutheria. All of these animals were small, rodent-like mammals. The researchers also discovered a new species of tree-dwelling mammal, Arboroharamiya fuscus.
The scientists used scanning electron microscopy to measure a total of 2,159 fossilized melanosomes to refine their color predictions. The fossilized melanosomes were all slightly elongated spheres and had far fewer differences in shape than in modern mammals. The researchers used their model to predict reflectance curves based on the shapes of the fossil melanosomes to determine the ancient mammals’ colors. They found that all the extinct mammals they examined likely had dark brown fur without any color patterns.
Based on these findings, the researchers suggested that most, if not all, early mammals were nocturnal, like many dark-colored mammals today. They suggested that this nocturnal lifestyle probably helped them survive the meteorite impact that wiped out the dinosaurs 100 million years later. While dinosaurs were unable to survive in the post-impact wasteland, these smaller, dark-colored mammals were more resilient and thrived in the aftermath. As mammals filled the ecological roles left by the dinosaurs, they evolved new color patterns, some based solely on camouflage, and others on new factors, like sexual selection and visual communication.
The researchers concluded that their model can predict fossilized mammal colors and help determine how these ancient animals lived. Notably, their data suggest that mammals likely stayed small and nocturnal throughout the Mesozoic until the dinosaurs were gone. Future researchers could use similar methods to uncover exactly how mammals evolved the colors we see today. For example, studying mammals closer to the impact event could reveal if it took a long time to develop diverse fur patterns, or if they began before the dinosaurs’ demise. Ultimately, similar studies could help determine whether the extinction of dinosaurs was necessary for the rise of mammals.
What it means: Coprolites are fossilized poop. Scientists have found coprolites from animals as diverse as fish, dinosaurs and saber-toothed cats. Teeth in the saber-toothed cat poop indicated that it had been eating baby sloths, which frankly feels a bit unfair from a creature with 11-inch-long (28 centimeters) teeth.
These fossils form when poop gets rapidly buried and mineralized instead of rotting away. Coprolites can be hard to match to the animal that produced them, but undigested bones and teeth in the fossilized poop can often provide clues to the kinds of animals that other animals eat.
How to use it in a sentence: If you're ever in a science museum and a volunteer, with a twinkle in their eye, asks you what you think a chunky, rock-looking thing is, the answer is always coprolite.
Can you crack our science word of the day puzzle, Chain Word?
Some 66 million years ago, an asteroid impact wiped out three-quarters of all plant and animal species on Earth, most notably taking down the dinosaurs. But exactly how that impact caused those extinctions has been the subject of fierce debate. According to a new paper published in the Journal of Geophysical Research: Biogeosciences, the impact would have produced an immense cloud of dust that superheated the upper atmosphere, charbroiling living organisms unable to take shelter and igniting widespread wildfires.
As previously reported, the most widely accepted explanation for what triggered that catastrophic mass extinction is known as the “Alvarez hypothesis,” after the late physicist Luis Alvarez and his geologist son, Walter. In 1980, they proposed that the extinction event may have been caused by a massive asteroid or comet hitting the Earth. They based this conclusion on their analysis of sedimentary layers at the Cretaceous-Paleogene boundary(the K-Pg boundary, formerly known as the K-T boundary) found all over the world, which included unusually high concentrations of iridium—a metal more commonly found in asteroids than on Earth. (That same year, Dutch geophysicist Jan Smit independently arrived at a similar conclusion.)
Since then, scientists have identified a likely impact site: a large crater in Chicxulub, Mexico, in the Yucatan Peninsula, first discovered by geophysicists in the late 1970s. The impactor that created it was sufficiently large (between 11 and 81 kilometers, or 7 to 50 miles) to melt, shock, and eject granite from deep inside the Earth, probably causing a megatsunami and ejecting vaporized rock and sulfates into the atmosphere. It has been estimated that the impact would have released energy over a billion times higher than the atomic bombs dropped on Hiroshima and Nagasaki in 1945.
New analysis of dust deposits left after the massive asteroid hit Earth around 66 million years ago suggests the event created a thick, worldwide dust blanket that drove heat down toward the planet’s surface, resulting in global wildfires.
The researchers behind the new study said the evidence for a post-impact dust blanket and resulting heat wave adds new fuel to the debate about what role, if any, the Chicxulub asteroid played in their extinction, by suggesting most unsheltered animals would have died instantly.
Scientists Debate Connection Between Asteroid Impact and Dinosaur Extinction
While scientists agree that a massive chunk of space rock slammed into Mexico’s Yucatan Peninsula 66 million years ago, they have continued to debate the event’s impact on the end of the dinosaurs‘ reign. Still, the timing of the two events, and the evidence for a mass extinction of animals incapable of seeking the necessary shelter to survive the asteroid’s impact, has led most to connect the two events to some degree.
Further studies of the impact have shown that the event’s immense heat and pressure vaporized a massive amount of rock, resulting in a huge cloud of dust and rock vapor high into the Earth’s atmosphere. As some of that dust condensed into tiny rock ‘spherules’ and slammed back into the surface, the friction between them and the air generated a corresponding heat pulse.
According to the authors of the new study, many theories suggested that this heat pulse acted like a planetary-wide broiler, including “radiating enough heat to sizzle thin-skinned animals without shelter,” but not enough for plants to suddenly burst into flames. The team said that this result temporarily caused researchers to move away from the idea that the immediate impact event caused the dinosaur’s extinction rather than a longer, more drawn-out event.
Now, after years of new ideas, the team said that a 2023 discovery once again changed the debate, leading to their new proposal.
Atmospheric Layer of ‘Post-Impact’ Dust Would Have Magnified Heat Wave 3.5 Times
According to the team’s statement, the 2023 discovery involved a layer of “extremely fine post-impact dust” that could have formed from rock vapor that did not condense into spherules.
“It reinvigorated my interest in what happened to the leftover vapor,” explained Brandon Johnson, a planetary scientist at Purdue University and lead author of the study detailing the new theory, “that’s where this work started.”
To determine what effect such a post-impact dust layer might have had on dinosaurs and other terrestrial animals, the team plugged the new data into previous simulations of the Chicxulub event. Johnson and colleagues especially wanted to know how the dust layer would boost Earth’s retention and release of heat energy generated by the falling rock spherules.
After running several simulations, the team determined that the dust layer would have increased the surface heat by 3.5 times compared to an event that only included the falling spherules. Unlike earlier models, this new version with the dust layer included showed that the heat pulse would have been enough to “kill animals and start spontaneous forest fires.”
“We’re in the realm where we might be essentially killing off everything within that first hour or two,” Johnson explained.
Notably, the researcher said his team’s concept is not unlike alternative extinction theories that credit a global post-impact winter for the eventual mass extinction of dinosaurs and other lifeforms.
“It seems counterintuitive,” Johnson said, “but actually it’s the same effect.”
The research compared the idea to how an insulated mug can keep hot coffee hot and iced coffee cold.
“Once the spherules finished falling and the fires petered out, massive dust clouds could have blocked warmth from the Sun for years to decades and caused a global winter,” the authors explained.
Results Could Help Unravel Why Some Animals Survived, and Others Didn’t
When discussing how the team’s findings might affect the ongoing debate about dinosaur extinction, Johnson said the work seems to offer strong support to the impact extinction theory.
“This work of ours supports this idea that it really is the impact that was devastating to terrestrial life and caused the mass extinction,” the researcher explained.
Although the team suspects that the global fires caused by the dust amplified the heat wave, they point out that a more complete geological record would likely be needed to provide confirmation. Alfio Alessandro Chiarenza, a paleontologist at University College London who was not involved with this study, said researchers could find a record of global wildfires, but “we just don’t have it so far.”
“It would be great to figure out which animals survived right at the impact and what their biological features were,” Chiarenza added. “This could finally tell us why some animals made it when others, like the dinosaurs, didn’t.”
Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org
Although the international team behind the discovery, which includes researchers from Paris, Brussels, and Vienna, said the evidence for this category of “oddball” meteorite offers a viable solution to its mysterious composition, they note that the rarity of chondrite meteorites makes its origin a new mystery that needs to be solved by future research.
They also note that a chondrite meteorite impact would have much less effect on atmospheric sulfur, which is critical to most extinction models, potentially casting doubt on its central role in dinosaur extinction.
Many Details About the Dinosaur Killer Meteorite Remain a Mystery
According to a statement, the Cretaceous-Paleogene impactor resulted in one of the largest extinction events in the planet’s history. While most scientists agree that the event played a significant role in ending the dinosaurs’ reign, the study’s authors note that “the exact mechanism and the extent of the impact-extinction link are debated.” They also note that the origin and composition of the dinosaur killer have remained a mystery.
An analysis of the Chicxulub impact structure reveals that the doomsday dinosaur-killer meteorite was between 10 and 15 kilometers (approximately 6 to 9 miles) wide. Estimates also suggest it impacted Earth at 64,000 km/m (40,000 mph) beneath the modern-day Yucatán Peninsula in Mexico.
Although previous studies identified the meteorite as similar to carbonaceous chondrites, the researchers said that carbonaceous chondrites are a diverse class of space rock, “leaving the exact nature of the impactor unclear.”
“Carbonaceous chondrites of the Ornans class (CO) are definitely not like the typical meteors you find in museum collections,” explained study co-author and visiting professor Dr. Philippe Claeys.
For example, the professor explained, a CO contains fewer volatile elements, such as zinc, carbon, Sulphur, and H20 “than other classes of meteorites we’ve discovered so far on Earth.”
One Mystery Solved
To try to unravel the mystery of the dinosaur-killer meteorite, the researchers teamed up with scientists from the Institut de Physique du Globe and the Université de Paris to conduct high-precision nickel isotope measurements of meteor samples from the event that have been collected over the years from the thin, worldwide layer of clay created by the explosive impact.
Dr. Claeys, a professor at Vrije Universiteit Brussel, currently visiting the Pacific Center for Isotopic and Geochemical Research in Earth, Ocean and Atmospheric Sciences at UBC, noted the challenging nature of the isotopic analysis, primarily due to the limited number of samples.
“Only a minute fraction of the projectile is preserved in the planet’s KT clay layer because the entire meteorite vaporized upon impact,” the researcher explained.
Still, the study authors explain, evaluating Nickel isotopes offers several advantages over other testing methods. For example, Nickel has five isotopes that the researchers note “allow for up to three separate internally normalized signatures.” They also highlight the availability of Nickel in “virtually all types of available early Solar System solids,” including iron meteorites, which allows for comparison with a wide variety of potential impactors.
Finally, they write, CI chondrites have a distinct Ni isotope signature from the rest of the class, therefore “making it possible to distinguish a CI-like impactor clearly” from other meteorite types.
After completing an isotopic analysis of samples of marine clays containing microscopic pieces of the ejecta, the team said their results “constrain the impactor to one group of carbonaceous chondrites, CO chondrites, “ as well as some evidence for “ungrouped chondrites.”
“By combining our new Ni isotope data with the existing evidence, we demonstrate that the composition of the Chicxulub impactor was most likely CO chondrite-like,” the researchers write, adding that this identification is possible “given nickel’s high abundance in primitive meteorites compared to the Earth’s crust and the distinct isotope compositions they record.”
A New Mystery is Created
While the isotopic analysis offers a compelling solution to the composition of the famed dinosaur-killer that slammed into Earth millions of years ago, the team said the identification casts doubt on the extent of its role in the dinosaurs’ extinction. Specifically, they note that CO chondrites are “dry” compared to others in their class, meaning they contain much less of the volatiles that most extinction theories cite as a significant mechanism.
“As highly volatile elements, such as C, N, and S, in CO chondrites are less abundant than in the typical CCs, questions arise whether the impactor was an essential contributor to the volatiles released during the impact,” they explained.
The most important volatile in most extinction theories is Sulfur (S). However, the authors note, CO chondrites would deliver “approximately half as much S” as more common types.
If the new analysis is correct, it also puts the dinosaur-killer’s origin in question. The authors note that possible sources include distant, debris-rich regions of the outer Solar System or even the outer area of the asteroid belt near Jupiter.
Combined with the compositional analysis lacking volatiles, the team notes that their findings allow “further studies of the mechanism behind the extinction.”
Finding “Doesn’t Alter Our Theory” of What Caused Land Dinosaur Extinction
When discussing the potential implications of their findings, the researchers said their study “highlights the extraterrestrial origin of the K-Pg mass extinction and the isotopes of Ni as a well-suited tool to characterize the nature of extraterrestrial material on Earth.” They also note that the composition of the dinosaur-killer “opens the door for further research into the connection between the impact and the mass extinction.”
From a scientific perspective, the research said their work “highlights the use of Ni isotopes in fingerprinting extraterrestrial materials on Earth,” and helps evaluate the risks associated with “potential future impact events and their consequences.” The study also shows how even an uncommon type of space rock can permanently alter the planet’s history.
“Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were,” Dr. Claeys said.
The researcher also noted that the lack of volatiles in this category of meteorite “doesn’t alter our theory of what caused the extinction event.” However, he notes, if correct, the result “makes it less likely that Sulphur contained in the impactor was the smoking gun.” Instead, the fine debris “thrown into the atmosphere” by the forceful impact would have been the primary factor in the end of the dinosaurs.
Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org
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