Self-Motivation
David Goggins
Former Navy Seal
Career Development
Bryan Cranston
Actor
Critical Thinking
Liv Boeree
International Poker Champion
Emotional Intelligence
Amaryllis Fox
Former CIA Clandestine Operative
Management
Chris Hadfield
Retired Canadian Astronaut & Author
Learn
from the world's big
thinkers
Start Learningfrom the world's big
thinkers
How DNA revealed the woolly mammoth's fate – and what it teaches us today
Scientists uncovered the secrets of what drove some of the world's last remaining woolly mammoths to extinction.
04 July, 2020
Ethan Miller/Getty Images
Every summer, children on the Alaskan island of St Paul cool down in Lake Hill, a crater lake in an extinct volcano – unaware of the mysteries that lie beneath.
<p>
It was here, on a winter expedition, that scientists uncovered the secrets of what drove some of the world's last remaining woolly mammoths to extinction, and when it happened.
</p><p>
Dr Beth Shapiro is a paleo-geneticist, who co-runs the
<a href="https://pgl.soe.ucsc.edu/" target="_blank">Paleogenomics Lab</a> the University of California, Santa Cruz.
</p><p>
Using modern genomics techniques, her team looks back at the past to understand how species and populations have evolved through time, based on their DNA. It then applies those lessons to the conservation of endangered species today.
</p><p>
The genetic material from animals that lived in the northern hemisphere during the Ice Age, including bison, wolves, mammoths and horses, is particularly well preserved.
</p><p>
Dr Shapiro is able to extract DNA from samples, such as teeth, to see how species differed genetically and learn when populations were growing, when they were shrinking, when individual animals might have been moving long distances – and when they could not.
</p><p>
"Connectivity is a crucial part of many of these species' extinction stories," says Dr Shapiro.
</p><p>
And this is true of the fate of St Paul Island's woolly mammoths.
</p><iframe allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/D1_Y8tqigo4" width="560">
</iframe>
<h3>When did mammoths roam the Earth?</h3><p>
Mammoths <a href="https://www.discovermagazine.com/planet-earth/uncovering-the-secrets-of-mammoth-island" target="_blank">lived on North America's mainland until about 10,000 years ago</a>, but they survived in two places for much longer: St Paul Island and Wrangel Island, in the Russian Arctic, where teeth have been found that are only 4,000 years old.
</p><p>
St Paul is a volcanic island that until around 9,000 years ago was connected to the mainland by the Bering Land Bridge, which enabled animals to roam freely to and fro.
</p><p>
But as the climate warmed and sea levels rose, it became isolated – and the mammoths were trapped. They were the only large mammal on the island, with no predators and, speaking at a <a href="https://www.weforum.org/events/world-economic-forum-annual-meeting-2020/sessions/the-young-science-of-ancient-dna" target="_blank">BetaZone session at Davos</a>, Dr Shapiro said it would have been a "mammoth utopia".
</p><iframe width="560" height="315" src="https://www.youtube.com/embed/0CjCDRgPnqk" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>
<h3>How did a lake reveal what happened?</h3><p>
Dr Shapiro explains: "Lakes are brilliant sources of ancient DNA, because they are a sink for genetic material during the summer. Lake Hill is the only source of fresh water on St Paul. So all the animals wander in to drink and the DNA they deposit sinks to the bottom and then freezes.
</p><p>
"Over time, you get accumulation like a stratigraphy of layer upon layer of everyone that was present on the island from the past to the present day. We knew if we could get a copy of this, we could figure out who was there, when and with whom."
</p><p>
On their winter expedition to Lake Hill, Dr Shapiro's team drilled down through the ice of the lake to the gravel at the bottom and extracted a core.
</p><p>
The genetic material, they later learned, dated back to 17,000 years ago.
</p><p>
"We took tiny little plugs of DNA all the way to the top, to the present day, and looked for mammoth DNA. We also looked at the vegetation and components of the lake itself to see if it was changing over time. Microscopic algae and microscopic animals, for example, can tell us whether the lake was salty or not and how shallow it was."
</p>
<h3>Why did the St Paul Island mammoths die?</h3><p>All of that data fit together like a jigsaw puzzle to show Dr Shapiro what had happened.</p><p>Mammoth DNA was present all the way from the bottom until around 5,600 years ago. Nothing changed with the vegetation, says Dr Shapiro, so they didn't run out of food.</p><p>"But everything else about the lake changed: the water chemistry changed; the rate of sediment accumulation changed. And that community of microorganisms completely turned from one that thrives in clear, deep fresh water to a community that prefers to live in very shallow, cloudy and slightly salty water."</p><p>All of which meant there had been a severe weather event, a drought, on St Paul Island. The lake started to dry up and the mammoths were left with nothing to drink.</p><p>"Had it happened 13,000 years ago, mammoths would have had another option. They could have wandered onto the mainland and looked for another source of fresh water. But they couldn't because they were on an island completely isolated, cut off from the mainland. Stuck. And so they became extinct."</p>
<h3>How can we protect isolated habitats today?</h3><p>Dr Shapiro warns the isolation that killed the mammoths on St Paul is threatening other species and biodiversity today.</p><p>"Islandization takes different forms where the habitats that we've chosen to protect are surrounded not by water, but by other things like farms and agriculture. By roads and highways and freeways. And by cities of all sizes.</p><p>"This places the plants and animals that live in these island habitats in a precarious situation. An extreme weather event or the introduction of a predator or disease can upset the balance of interactions taking place within these habitats, potentially leading to extinction."</p><p>Studies of other ancient animals using the same method, from woolly rhinos to Arctic horses and species of lion, have also shown connectivity is a key factor in extinction. <br></p><p>"The populations that remained became increasingly isolated from each other, both geographically and genetically, with each of these island populations functioning as their own tiny, isolated thing."</p><p>Any plan to protect and preserve endangered species must also give animals routes of escape to move between habitats or find new ones as the climate warms.</p><p>"This could mean building overpasses where animals can cross highways. We could create greenways, green roofs, city parks, green corridors along rivers and roads, and not just build walls or barriers that further fragment this already fragmented landscape."</p><p>The Yellowstone to Yukon Conservation Initiative is an example of an organization doing just that – aiming to link Yellowstone National Park in the Western United States with the Yukon in Canada, where Dr Shapiro does most of her work.</p><p>"A sustainable future for biodiversity will require creativity," she says. "But it will also require collaboration."</p><p>Reprinted with permission of the <a href="https://www.weforum.org/" target="_blank">World Economic Forum</a>. Read the <a href="https://www.weforum.org/agenda/2020/06/dna-reveal-woolly-mammoth-fate-beth-shapiro/" target="_blank">original article</a>.</p>
Keep reading
Show less
This ancient crocodile walked on two legs 'like humans'
Batrachopus grandis, an ancient crocodylomorph, may have chased down land prey on its own two feet.
15 June, 2020
(Photo: Anthony Romilio/University of Queensland)
<ul class="ee-ul"></ul>
<p>As any schoolchild will tell you, crocodiles have remained unchanged for millions of years. These powerful ambush predators have evolved to fit perfectly within their niche. They are so successful that they <a href="https://www.amnh.org/exhibitions/dinosaurs-ancient-fossils/extinction/dinosaurs-survive" target="_blank">survived the K-T extinction</a>, outliving the dinosaurs and many other reptile species they once shared the planet with. Fossils have even been discovered that are virtually identical to today's crocs, which is why they are often (<a href="https://www.nationalgeographic.com/science/phenomena/2015/11/16/crocodiles-are-not-living-fossils/" target="_blank">and wrongly</a>) referred to as "living fossils."</p><p>That's the extant lineage, though. Fossils have also shown <a href="https://ucmp.berkeley.edu/taxa/verts/archosaurs/crocodylomorpha.php" target="_blank">crocodylomorphs</a>, the group of archosaurs that include crocs and their relatives, to be a dynamic branch of the tree of life, and earlier crocodylomorphs weren't as evolutionarily conservative as their contemporary cousins. </p><p>A recent discovery in South Korea suggests one crocodile relative even took to the land on its own two feet.</p>
Walking the walk
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM5MjIyOS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwMDM5NDYxN30.vSptOKk7U7Vi6UGUrVSrlDZDA0KE27a4Hi506qS7_MQ/img.jpg?width=1245&coordinates=0%2C0%2C145%2C0&height=700" id="4984d" class="rm-shortcode" data-rm-shortcode-id="ca91bf364c9dcf5752919b5105bbcb2f" data-rm-shortcode-name="rebelmouse-image" alt="A photograph of Batrachopus grandis track impressions found at Jinju Formation." />A photograph of Batrachopus grandis track impressions found at Jinju Formation.
<p>The evidence comes from trace fossils found at the Jinju Formation, South Korea. The site houses nearly one hundred 24-centimeter footprints made during the Early Cretaceous period (110–120 million years ago) in what was likely muddy sediment. Researchers originally believed these fossils were left by a <a href="https://www.amnh.org/exhibitions/pterosaurs-flight-in-the-age-of-dinosaurs/what-is-a-pterosaur" target="_blank">pterosaur</a>, a flying reptile that lived in that period.</p><p>"Fossil crocodile tracks are quite rare in Asia, so finding an abundance of nearly one hundred footprints was extraordinary," Anthony Romilio, a paleontologist at the University of Queensland and a member of the research team, said <a href="https://stories.uq.edu.au/news/2020/ancient-crocodiles-walked-like-dinosaurs/index.html" target="_blank">in a release</a>. "As an animal walks, the hind feet have the potential of stepping into the impressions made by the hand and 'over-printing' it, but we find no evidence of this at these Korean sites.</p><p>"It isn't due to poor preservation either, because these fossils are spectacular, they even have the fine details of the toe-pads and scales on their soles preserved."</p><p>That excellent preservation led researchers to reassess the fossils. They noticed the tracks were flat and sported deep heel impressions, meaning they weren't left by dinosaurs or their bird relatives. </p><p>"They were moving in the same way as many dinosaurs, but the footprints were not made by dinosaurs," Kyung Soo Kim of Chinju National University of Education, who led the research team, said <a href="https://www.sciencedaily.com/releases/2020/06/200611114542.htm" target="_blank">in the same release</a>. "Dinosaurs and their bird descendants walk on their toes. Crocodiles walk on the flat of their feet leaving clear heel impressions, like humans do."</p><p>Based on the flat-footed gait and skin traces, the researchers concluded the footprints belonged to a <em>Batrachopus</em>, a type of crocodylomorph <a href="https://www.ldeo.columbia.edu/~polsen/nbcp/olsen_padian_86.pdf" target="_blank">commonly found in Mesozoic North America</a>. </p><p>But there is something unique about these tracks. A typical crocodile leaves a wide trackway due to its squat stance. Conversely, the Jinju trackways are very narrow. As Kim put it, they look like "a crocodile balancing on a tight-rope." And while the site hosts well-preserved backfoot tracks, tail-drag marks and manus tracks (read: handprints) are conspicuously absent.</p><p>Taken together, the evidence suggests these crocodylomorphs walked on two legs. Based on the size of the footprints and their spacing, researchers imagined this crocodylomorph measured over three meters in length and strode on legs the same height as an adult human's. They named their discovery <em>Batrachopus grandis</em>.</p><p>The researchers published their findings in <a href="https://www.nature.com/articles/s41598-020-66008-7.pdf" target="_blank">the peer-reviewed Scientific Reports</a><u>.</u></p>An evolving understanding
<div class="rm-shortcode" data-media_id="bM8XiiEp" data-player_id="FvQKszTI" data-rm-shortcode-id="217e12c49e7fd202232637b5487313ba"> <div id="botr_bM8XiiEp_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/bM8XiiEp-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/bM8XiiEp-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/bM8XiiEp-FvQKszTI.js"></script> </div> <p>For now, the only evidence for <em>Batrachopus grandis</em> exists in the footprints, so there's still much to learn about it. In the study, the researchers note the possibility that this crocodylomorph didn't take to the land but used its hind legs to propel itself through waterways.</p><p>Not all paleontologists agree with the study's conclusions. Phil Manning, a paleontologist at the University of Manchester, who was not part of the research, <a href="https://www.bbc.com/news/science-environment-53011567" target="_blank">told the BBC</a><u> </u>he found the trace fossils interesting but didn't think a crocodilian was capable of producing them.</p><p>"Look at any videos of living crocs and the rotation of their feet when they're galloping: it's outwards, not inwards towards the midline of the trackway. Just from their orientation, it looks more like some kind of dinosaurian track-maker to me. But whether it's a croc - unfortunately, we just don't have the fossil bones to tell us," he said.</p>Plenty of crocs in the fossilized sea
<p>If you had your heart set on a land-roaming, bipedal crocodile, don't be disappointed. The ancient world was filled with enough strange and eerie crocodylomorphs to fill many a nightmarish menagerie.</p><p>In 2015, for example, paleontologists discovered a crocodile relative in North Carolina. This 9-foot-long apex predator also walked on two feet and ruled its Pangaean stomping grounds until the Triassic-Jurassic extinction event ended its reign. Paleontologists christened this species <em>Carnufex carolinensis</em>, or the "<a href="https://www.pbs.org/newshour/science/newly-discovered-bipedal-crocodile-ancestor-terrorized-pre-dinosaur-world" target="_blank">Carolina Butcher</a>."</p><p>There's also evidence for crocodiles that <a href="https://www.youtube.com/watch?v=qruxOVmSfyY" target="_blank">snatched sauropods from the water's edge</a>, crocodiles that bounded through ancient forests <a href="https://www.youtube.com/watch?v=QmdcewIjXi0" target="_blank">on hooves</a>, and crocodiles that enjoyed <a href="https://www.smithsonianmag.com/smart-news/ancient-crocodiles-would-have-ordered-salad-180972518/" target="_blank">leafy flexitarian diets</a>. Even their modern relatives continue to surprise us, such as their <a href="https://www.wired.com/2014/02/crocodiles-can-climb-trees/" target="_blank">surprisingly agile tree-climbing abilities</a>.</p><p>So while these ancient creatures may be extinct, they continue to evolve in our imaginations. We'll have to see what science has in store for <em>Batrachopus grandis</em> as we discover more about it. </p>
Keep reading
Show less
Allosaurus dabbled in cannibalism according to new fossil evidence
These Jurassic predators resorted to cannibalism when hit with hard times, according to a deliciously rare discovery.
01 June, 2020
Stephanie K. Drumheller et.al
- Rare fossil evidence of dinosaur cannibalism among the Allosaurus has been discovered.
- Scientists analyzed dinosaur bones found in the Mygatt-Moore Quarry in western Colorado, paying special attention to bite marks that were present on 2,368 of the bones.
- It's likely that the predatory carnivore only ate their already-dead peers during times when resources were scarce.
<p>Rare fossil evidence of dinosaur cannibalism has been discovered by paleontologists in a large quarry near the Utah-Colorado border.</p><p><a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0233115" target="_blank">According to a study</a> published last week, May 27, in the journal <a href="https://dx.doi.org/10.1371/journal.pone.0233115" target="_blank">PLOS ONE</a>, scientists analyzed dinosaur bones found in the Mygatt-Moore Quarry in western Colorado. In their examination, the researchers paid special attention to bite marks that were present on the bones. While many bone-bites were identified as originating from <a href="https://ucmp.berkeley.edu/diapsids/saurischia/theropoda.html" target="_blank">theropod</a> dinosaurs, a diverse group of bipedal dinosaurs, there were cases where it was found that the bite marks were from the same genus as the bitten. Specifically, it appears that the predatorial beast <a href="https://www.livescience.com/24815-allosaurus.html" target="_blank"><em>Allosaurus</em></a>, a type of theropod, occasionally dined on its own kind, making this an exceptionally rare finding of dinosaur cannibalism.<br></p>
Desperate times call for cannibalism
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="cc909d1235ba9e4e5149f7e3580c8568"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/Y2ODPFiksBE?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>While scavenging and even cannibalism is relatively common among today's predators, the Allosaurus probably didn't eat their peers as a staple meal. According to Stephanie Drumheller, the study's lead author, they were likely driven to turn to cannibalism as a last resort when times were scarce in food supply. </p> <p>"Big theropods like Allosaurus probably weren't particularly picky eaters, especially if their environments were already strapped for resources.'' said Drumheller, a paleontologist in the University of Tennessee, Knoxville's Department of Earth and Planetary Sciences, <a href="https://www.eurekalert.org/pub_releases/2020-05/p-ise052120.php" target="_blank">in a statement</a>. "Scavenging and even cannibalism were definitely on the table."</p><p>The Mygatt-Moore Quarry is home to thousands of dinosaur bones dating back to the late Jurassic period, somewhere in the ballpark of 150 million years ago. When the quarry was at its prime, it was thriving with lush vegetation making it a cushy home for many large dinosaur species, including the long-necked lizard <a href="https://www.livescience.com/25093-apatosaurus.html" target="_blank">Apatosaurus</a>. The new study suggests, however, that at some point this dino sanctuary fell on some hard times, which forced local carnivores to scavenge for bits of meat from the picked-over carcasses of dead dinosaurs.</p>Study Findings
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM2NDg4MS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYwODAxOTMzOX0.X586xL4Ci-v4fwAaKZJAf7QOp7EANWKy9ScFV49l-us/img.png?width=980" id="992a1" class="rm-shortcode" data-rm-shortcode-id="acecfb3761e4e8b41e02b29bfd62452c" data-rm-shortcode-name="rebelmouse-image" />Fig 4. Dry season at the Mygatt-Moore Quarry showing Ceratosaurus and Allosaurus fighting over the desiccated carcass of another theropod.
Illustration by Brian Engh (dontmesswithdinosaurs.com)
<p>The researchers examined the bite marks on 2,368 dino bones from the quarry. Noting the width, depth, and pattern of the bite marks, the team was able to trace the chomp marks on the prey back to specific dinosaur species. Of those bones, 684, or 29 percent, were marked with at least one theropod bite. Many of those marks were imprinted by serrated teeth, suggesting to the researchers that Allosaurus (the most common theropod among the quarry's fossils) did a majority of the biting.</p><p>Allosaurus tended to feast mostly on herbivores. Yet, 17 percent of their bite victims were other theropods. That included some fellow Allosauruses, making this the first solid chunk of evidence of cannibalism in the species; a deliciously novel discovery. Interestingly, however, most of the bite marks that the scientists examined didn't appear to be killing wounds. More than half of all bite-marks found on the victim were on bony parts with little meat like fingers, toes and spinal columns. Not exactly the cut of meat a hunter with first-dibs would choose, suggesting that they were scavenging for the bare scraps. </p><p>Ultimately, these fossils tell a miserable story of dinosaurs down on their luck, left with no choice but to scrounge for measly scraps of meat off their own kin's rotting carcasses. </p>
Keep reading
Show less
Is poop-filled drinking water what killed ancient giant sloths?
Researchers think they know how a group of ancient sloths, who died thousands of years ago in Ecuador, met their untimely end.
15 May, 2020
Photo Credit: Wikimedia Commons
- Evidence collected from an ancient boneyard in Ecuador suggests that a group of 22 ancient giant sloths died in a wallow of their own feces.
- Other mammals, such as a deer, a horse, an elephant-like creature called a gomphothere, and another species of ground sloth were identified at the site.
- The fate of the sloths parallels that of modern hippos who can become lethally poisoned in times of drought when the feces to water ratio shifts in their watering holes.
<p>Evidence collected from a fossil trove in Ecuador suggests that a group of ancient giant sloths met their collective demise by wallowing in their own poop in what was once a prehistoric marsh.</p><p>In a new paper published in <a href="https://www.sciencedirect.com/science/article/abs/pii/S003101821930447X" target="_blank">Palaeogeography, Palaeoclimatology, Palaeoecology</a>, a team of paleontologists from the U.S. and Ecuador reached this conclusion by piecing together clues from the remains of 22 Panamerican ground sloths (<em>Eremotherium laurillardi) </em>discovered in what is now the Tanque Loma tar seep on Ecuador's southwest coast. The bones date back to 18,000 to 23,000 years ago.</p>
Discoveries from an ancient boneyard
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="0745aba719f914d2113ab181ef8201b8"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/vDCk0Uma2m4?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>An assemblage of 677 bones, 575 of which belonged to <em>E. laurillardi</em>, were found on this site in the Santa Elena peninsula in Ecuador. Other mammals, such as a deer, a horse, an elephant-like creature called a gomphothere, and another species of ground sloth were identified. Analysis of <em>E. laurillardi</em>'s bones reveal that the sloths likely died around the same time, evidenced by the lack of sediment separating them. They were also part of a multigenerational group, including at least 15 adults, one teen, and six children. This arrangement of remains and the range of ages indicates a mass mortality event, according to the researchers.</p><p>Giant ground sloths were once one of the most common large vertebrates living in the Americas. <a href="https://advances.sciencemag.org/content/5/2/eaau1200?rss=1" target="_blank">Prior research</a> indicates that the species, which can reach lengths of 19 feet, were widely distributed across the region ranging from southern Brazil to North America's Gulf and Atlantic coasts. We also know that they died out 11,000 years ago. But little has been known about their behavior and social structure, which is why this latest find is so exciting.</p><p>While modern sloths are solitary creatures, the paper suggests <em>E. laurillardi</em> were rather gregarious creatures who congregated near water. Tanque Loma was probably once a marshy watering hole where the sloths cooled off, bathed, and quenched themselves similar to warthogs and hippopotamus populations today. </p>Clues point to a crappy death
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzI4MzE2My9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyODU1NzY3OX0.91lo89Xr_jBdsvWSkKTbHwNOJWv7jBnd7YuA4q6Z1_U/img.jpg?width=1245&coordinates=0%2C326%2C0%2C0&height=700" id="78782" class="rm-shortcode" data-rm-shortcode-id="daf9283b05bad90707373531acf5a906" data-rm-shortcode-name="rebelmouse-image" alt="pod of hippos" />Photo Credit: Jeff Griffith / Unsplash
<p>Prior analysis suggested that the asphalt on the site seeped into the sloths' gravesite after the bones had already been deposited, thus ruling out death by asphalt poisoning. Death by volcano or other natural disaster is also unlikely because the sediments do not contain ash or charcoal. And because the sloths across a full range of age groups are present, their death probably wasn't caused by disease or a predatory attack, either. In those cases, there would be an overrepresentation of old and young.</p><p>Rather, the researchers believe the sloths died another way.</p><p>"Taking observations from modern megafaunal ecosystems as an analogue, we suggest that this death event could have resulted from drought and/or disease stemming from the contamination of the wallow, paralleling situations observed among hippopotamus populations in watering holes on the present-day African savannah," write the researchers in the paper.</p><p>The scientists suspect that the fate of some hippopotamus groups may point to what happened to these 22 ancient giant sloths. Hippos are apparently <a href="https://www.sciencealert.com/hippopotamus-faeces-causes-water-hypoxia-kills-fish" target="_blank">prolific poopers</a>. So much so that the amount of their waste can change the chemistry of water they spend their days in to the point of sometimes killing all the fish. It can even, sometimes, kill the hippos in times of drought when the feces to water ratio shifts.</p><p>"Based on the data from this study, a modern analogue to the Tanque Loma <em>E. laurillardi</em> assemblage may be hippopotami, which congregate in large numbers at water sources where they spend most of their time submerged to protect themselves against heat, sun and insects," <a href="https://www.sciencedirect.com/science/article/abs/pii/S003101821930447X" target="_blank">the researchers wrote</a>. "In times of drought, as these water sources begin to dry up, surrounding vegetation disappears and the wallows become increasingly polluted with hippopotamus faecal material, causing significant detrimental impacts on the watershed ecosystem." </p><p>Besides bones, the team found plant material in <em>E. laurillardi</em>'s fossil bed. Interestingly, this was not living plant material—it had been digested and excreted. This supports the theory that the ancient sloths met their unfortunate demise in a slop of their own feces.</p>
Keep reading
Show less
New fossils reveal first known swimming dinosaur
Non-avian dinosaurs were thought terrestrially bound, but newly unearthed fossils suggest they conquered prehistoric waters, too.
01 May, 2020
<ul class="ee-ul"></ul>
<p>Despite being extinct for <a href="https://www.usgs.gov/faqs/when-did-dinosaurs-become-extinct?qt-news_science_products=0#qt-news_science_products" target="_blank">65 million years</a>, dinosaurs continue to <a href="https://qz.com/1579292/our-knowledge-of-dinosaurs-is-evolving-so-is-how-we-depict-them/" target="_blank">evolve in our imaginations</a>. Over the past two hundred years of research, these once terrible lizards have added a panoply of new adaptations, from brightly colored feathers to a <a href="https://www.cbc.ca/news/technology/dinosaur-sounds-honk-growl-torah-kachur-1.3803212" target="_blank">syrinx</a> more appropriate for mate-attracting honks than movie-monster roars.</p><p>Despite these many changes, one taxonomic rule seemed steadfast: <a href="https://bigthink.com/kevin-dickinson/what-makes-a-dinosaur-a-dinosaur" target="_self">Non-avian dinosaurs</a> lived terrestrial lives. If Mesozoic reptiles flew, like <a href="https://www.smithsonianmag.com/science-nature/why-a-pterosaur-is-not-a-dinosaur-87082921/" target="_blank"><em>Pterodactylus</em> and <em>Pteranodon</em></a>, then they were not dinosaurs. If they swam, like <a href="https://en.wikipedia.org/wiki/Ichthyosaurus" target="_blank"><em>Ichthyosaurus</em></a><em> </em>or <a href="https://en.wikipedia.org/wiki/Plesiosauria" target="_blank"><em>Plesiosaurs</em></a>, then they were not dinosaurs.</p><p>But new <em>Spinosaurus aegyptiacus</em> fossils excavated in the Kem Kem region of the Moroccan Sahara may have rewritten those rules and our understanding of the Mesozoic world. </p>
Unearthing a mystery in the desert
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzE4MDU1OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNzI1NTExM30.1L90N5rrjAiYqBzRa72_b3hmP8Bq20MdZ3KtdfSgUTg/img.jpg?width=1245&coordinates=0%2C24%2C0%2C262&height=700" id="765d6" class="rm-shortcode" data-rm-shortcode-id="45a87235d3fe79b339ade44f58f9818c" data-rm-shortcode-name="rebelmouse-image" />Stromer's holotype of his original Spinosaurus specimen.
<p>Spinosaurus was a Cretaceous period therapod, a clade of dinosaurs that include <em>Velociraptor</em>, <em>Dilophosaurus</em>, <em>Giganotosaurus</em>, and of course, <em>Tyrannosaurus rex</em>. At nearly 40-feet long and weighing an estimated 6 tons, Spinosaurus is one of the largest predatory dinosaurs ever discovered, yet many of its characteristics have confounded paleontologists for decades.</p><p>The first Spinosaurus fossils were discovered in 1912 by <a href="https://blogs.scientificamerican.com/tetrapod-zoology/the-discovery-and-early-interpretation-of-spinosaurus/" target="_blank">Ernst Freiherr Stromer von Reichenbach</a>, a paleontologist and German aristocrat. Stromer's specimen mainly consisted of jaw fragments and neural spines, but that proved enough to convince him of his discovery's peculiarities. </p><p>Unlike T. rex's stout, powerful jaw, Spinosaurus had a slender yard-long snout more akin to a crocodile's. Its conical teeth were ill-suited to shearing and tearing like other therapods' serrated teeth; they were a better match for snapping the fish out of water. Then there was that characteristic spine sail.</p><p>Unfortunately, Spinosaurus would remain elusive to Stromer as his original specimen was destroyed in the Allied bombing raids on Munich. Over the decades, however, paleontologists would keep trying to solve the puzzle of Stromer's weird dinosaur.</p>A digital resurrection
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzE4MDU1OS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTU5NTM2MTExOX0.YuUzxvnm_mHQYTvH2e_Xjq4pKjE_U7R5HEf-xc1TfVc/img.png?width=1245&coordinates=92%2C0%2C93%2C0&height=700" id="c2e6e" class="rm-shortcode" data-rm-shortcode-id="b58ca0abb324db9a0fd7851490615a89" data-rm-shortcode-name="rebelmouse-image" />An illustration of a Spinosaurus skeleton with its thinner, more traditionally therapod-like tail.
<p>And Spinosaurus kept getting weirder. In addition to the back-sail and elongated jaw, further fossil discoveries elucidated a dinosaur that was incredibly front-heavy with dense bones and short back legs not tailored for running.</p><p>"I tried to see all the bones, the muscles, the connective tissue, everything," Nizar Ibrahim, a paleontologist at the University of Detroit Mercy, <a href="https://www.nationalgeographic.com/magazine/2014/10/" target="_blank">told <em>National Geographic</em></a><em>. </em>"Sometimes it was there for an instant, then it vanished, like a mirage. My brain couldn't quite compute all that complexity."</p><p>As <a href="https://www.nationalgeographic.com/news/2014/9/140911-spinosaurus-fossil-discovery-dinosaur-science/" target="_blank">reported in <em>National Geographic</em></a>, Ibrahim teamed up with Simone Magnuco at the Milan Museum and University of Chicago fossil preparator Tyler Keilor in 2014 to digitally resurrect Spinosaurus. </p><p>The team used a CT scanner to reconstruct <a href="https://www.nytimes.com/2014/09/12/science/a-nomads-find-helps-solve-the-mystery-of-the-spinosaurus.html" target="_blank">Spinosaurus bones</a> within a computer, including some unearthed by Ibrahim in Morocco. They rounded out their skeleton by assembling missing bones from images of museum specimens, Stromer's original photographs and sketches, and those from other therapod specimens.</p><p>When they saw Spinosaurus walk across its digital landscape, they realized the animal was better attuned for an amphibious lifestyle than a terrestrial one. It had nostrils at the tip of its snout. Its bones were dense like aquatic mammals, and its hind legs would not have been such a hindrance if submerged in buoyant hunting grounds.</p><p>Their hypothesis also fits with what we know about Spinosaurus's habitat. Today, the Sahara is one of the driest places on Earth, but in the Cretaceous period, vast waterways covered the land and sported giant fish to outsize the most unbelievable of fish stories. (Seriously though, they were <em>this big</em>.)</p>A study of lost tails
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="0530ef75d9bc4d29b2bc7c7802ba98e9"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/fDhofM81RQE?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>But something was missing: a means of propulsion. How did a giant like Spinosaurus catch slick and quick prey while paddling like a duck on two stumpy hind legs? It didn't add up.</p><p>"The big thing we were missing was a propulsive structure because you can't really be an aquatic predator unless you have some way to catch prey in the water and move through the water," <a href="https://www.youtube.com/watch?v=fDhofM81RQE&t=66s" target="_blank">Ibrahim told <em>Nature</em></a>. "That's what we now found."</p><p>Between 2015 and 2019, on a grant from the National Geographic Society, Ibrahim and his team traveled to the Kem Kem region of the Moroccan Sahara to unearth further Spinosaurus fossils. During their dig, they discovered Spinosaurus tail vertebrae that were "characterized by extremely long spines."</p><p>Ibrahim's previous reconstruction of Spinosaurus featured a thin tail borrowed from other therapods. But such a tail would make traveling through the water unwieldy—think paddling a canoe with a walking stick. The new vertebrae revealed a fin-like tail, similar in appearance to a newt's, and could more easily propel the dinosaur through the water.</p><p>To test his hypothesis, Ibrahim's colleagues at Harvard crafted plastic models of the Spinosaurus tail. They attached it to a robot system that mimics swimming and measured its thrust and efficiency. They then compared the Spinosaurus tail's performance against two other therapod tails and extant aquatic animals.</p><p>Spinosaurus's results were consistent with the aquatic animals and superior to the terrestrial therapods. Ibrahim and his team published their results in <a href="https://www.nature.com/articles/s41586-020-2190-3" target="_blank"><em>Nature</em></a>. </p><p>"This discovery is the nail in the coffin for the idea that non-avian dinosaurs never invaded the aquatic realm," <a href="https://www.eurekalert.org/pub_releases/2020-04/ngs-nfr042920.php" target="_blank">Ibrahim said in a release</a>. "This dinosaur was actively pursuing prey in the water column, not just standing in shallow waters waiting for fish to swim by. It probably spent most of its life in the water."</p><p>But as is the case in science, not everyone is yet convinced.</p><p>Donald M. Henderson, the curator of dinosaurs at the Royal Tyrrell Museum, believes Spinosaurus likely lived at the water's edge, scooping up fish as they swam by. As he told <a href="https://www.nytimes.com/2020/04/29/science/spinosaurus-dinosaur-tail-swimming.html" target="_blank">the <em>New York Times</em></a>, he does not believe Spinosaurus would be a powerful swimmer.</p><p>"My first thing is, they haven't actually demonstrated that this tail could produce enough force to propel a six-and-a-half-ton body through the water," Henderson said. He added that the researchers had yet to provide that Spinosaurus had enough muscle power to move such a tail or compensate for the drag of its sail.</p>Dinosaurs are alive! Here’s how we know, and why it matters
<div class="rm-shortcode" data-media_id="nTfwl0kS" data-player_id="FvQKszTI" data-rm-shortcode-id="67c76febbfb51d2231c6bcef00459388"> <div id="botr_nTfwl0kS_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/nTfwl0kS-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/nTfwl0kS-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/nTfwl0kS-FvQKszTI.js"></script> </div> <p>As new fossils are found and new ideas to test emerge, we'll see if Henderson's concerns capsize the aquatic hypothesis or not.</p><p>Even if Spinosaurus is thrown out of the pool, that doesn't mean dinosaurs will forever remain grounded. As <a href="https://www.nytimes.com/2017/12/06/science/duck-dinosaur-swim.html?action=click&module=RelatedLinks&pgtype=Article" target="_blank">reported by the <em>New York Times</em></a>, a dinosaur fossil called <em>Halszkaraptor escuilliei</em> has features that suggest a partial aquatic lifestyle. These include "a neck like a swan, a snout like a goose, and forelimbs like flippers," but the specimen is so unusual that its authenticity remains a matter of debate. </p><p>And what is revealed in these debates will change our understanding of dinosaurs—both those that are gone and those that are still with us.</p>
Keep reading
Show less
Popular
