Rocks from two hundred million years ago show us how everything died and how nothing is new.
- A new study suggests that the mass extinction that gave dinosaurs the evolutionary upper hand was caused by oceanic oxygen deprivation.
- Using ratios of sulfur isotopes, researchers could estimate changes in ocean oxygen levels in ancient seas.
- The authors suggest a similar mechanism as that which can cause dead zones in oceans today caused a mass extinction.
How to tell what the world was like 201 million years ago using rocks<p>The mass extinction that ended the Triassic period was a massive die-off that saw somewhere between a quarter and a third of ocean life vanish alongside most large land <a href="https://en.wikipedia.org/wiki/Triassic%E2%80%93Jurassic_extinction_event" target="_blank">animals</a>. Plants were not spared a culling either, with perhaps 60 percent of plant species also dying. The event took less than 10,000 years to carry out this morbid work. This remarkable event paved the way for dinosaurs to become the dominant land animal during the Jurassic period, as most of their competition was dead.</p><p>Explanations for this event's cause have ranged from gradual climate change, to asteroid impacts, to rampant volcanism. New evidence suggests that <a href="https://en.wikipedia.org/wiki/Anoxic_event" target="_blank">ocean anoxia</a>, the depletion of oxygen supplies in the ocean, played a large role. </p><p>The researchers examined the levels of two isotopes of sulfur in rocks that would have been on the seafloor during the extinction event from British Columbia, Sicily, and Northern Ireland. The two isotopes, <sup>32</sup>S and <sup>34</sup>S, can become trapped in limestone and other rocks and exist at different ratios depending on how much oxygen is in the water around them. By examining the changes in the ratio of the two isotopes in rocks formed at the time, we can know what was happening to oxygen levels in the oceans hundreds of millions of years ago. </p><p>The scientists noticed "large spikes" in the ratio of <sup>34</sup>S to <sup>32</sup>S in the samples from all of the locations, indicative of a substantial fall in the amount of oxygen available. These findings can be applied far beyond the sites the rock samples came from, suggesting that oxygen levels fell across large portions of the globe-spanning superocean, known as <a href="https://en.wikipedia.org/wiki/Panthalassa" target="_blank" rel="noopener noreferrer">Panthalassa, </a>that existed alongside Pangea.<strong> </strong></p>
And you thought the Dead Zone in the Gulf of Mexico was bad.<iframe width="730" height="430" src="https://www.youtube.com/embed/yObCpYLLJSk" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p>This study isn't the only one suggesting Ocean anoxia caused the extinction event. A previous <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GC006941" target="_blank">study</a> from 2017 reached a similar conclusion by measuring the trace uranium levels in rocks formed at the time. Similarly to the ratio of sulfur isotopes considered above, the amount of uranium in these rocks varies with the amount of oxygen. That study suggests that the low oxygen levels may have lasted 50,000 years after their initial fall, with a full 250,000 years needed before coral reefs could <a href="https://phys.org/news/2017-08-global-oceanic-dead-zones-persisted.html" target="_blank">recover</a>.</p><p>In the present day, the researchers hypothesize that this anoxia was connected to significant volcanic activity at the time. By releasing massive amounts of greenhouse gasses, this would have both acidified the oceans by increasing their carbon content and lowered their oxygen levels by raising global temperatures, as warm water holds less oxygen <a href="http://limnoloan.org/waterquality/dissolved_oxygen/#:~:text=Warm%20water%20holds%20less%20dissolved,to%20escape%20from%20the%20water.&text=Therefore%20the%20warmer%20and%20saltier,dissolved%20oxygen%20it%20will%20contain." target="_blank">overall</a>. Together, these effects can annihilate marine <a href="https://en.wikipedia.org/wiki/Ocean_acidification#Ecosystem_impacts_amplified_by_ocean_warming_and_deoxygenation" target="_blank" rel="noopener noreferrer">ecosystems</a>. It is known that major volcanic activity was occurring at the time, lending credence to this <a href="https://en.wikipedia.org/wiki/Central_Atlantic_magmatic_province" target="_blank" rel="noopener noreferrer">hypothesis</a>. </p><p>It's a good thing that nothing is causing the oceans to heat up and have lower oxygen levels these days! Oh, <a href="https://en.unesco.org/sites/default/files/iucndeoxreportbook15-11-2019.pdf" target="_blank" rel="noopener noreferrer">wait</a>. Never mind. </p>
A rare titanosaur embryo was discovered with its skull preserved in 3 dimensions.
- Researchers have uncovered what the facial features of a baby titanosaurus embryo looked like using cutting-edge imaging technology.
- This in the first-ever discovery of a 3D embryonic titanosaurian sauropod skull.
- The embryo reveals that titanosaur babies had binocularly focused vision in the front of the head rather than on each side, retracted openings on their snout, and a single horn in the front of their head.
The discovery<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzYwNDExNy9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY2OTY1MzE2M30.tM0SmjB6Mf_-7LtWFlgUWATWeWMnx7r8iXj_TKNvyls/img.png?width=1245&coordinates=42%2C0%2C42%2C0&height=700" id="4fa4f" class="rm-shortcode" data-rm-shortcode-id="ac8d1beadf2cc442bb5a9c98763e7520" data-rm-shortcode-name="rebelmouse-image" alt="3D scan of fossil" data-width="1245" data-height="700" />
Kundrát et al., Current Biology, 2020<p>About 20 years ago, a dinosaur egg was illegally smuggled into the United States from Argentina. Unbeknownst to the egg-runner, it contained one of the most exquisitely preserved skulls of a dinosaur embryo ever found. (The egg has since been returned to Argentina.)</p><p>"The preservation of embryonic dinosaurs preserved inside their eggs is extremely rare," said John Nudds, study co-author and palaeontology professor at The University of Manchester, in a statement. "Imagine the huge sauropods from 'Jurassic Park' and consider that the tiny skulls of their babies, still inside their eggs, are just a couple of centimetres long."</p><p>The embryo comes from a group of dinosaurs named titanosaurian sauropods, who are known for their long necks and tails, and tiny heads. While their species also lay claim on the largest terrestrial animal ever known to have existed, they start off small enough to fit inside an egg roughly the size of that of an ostrich. The uncovered titanosaur skull is about the size of a table grape. </p><p>Understanding the species origins may give scientists a better idea of how they grew and developed. But the task hasn't been easy. Twenty-five years ago researchers struck a bonanza when they uncovered a Cretaceous-era nesting ground of these dinosaurs in Patagonia — a site where titanosaurian sauropods once laid their eggs 80 million years ago. But unfortunately, the eggs the researchers found in the area were flattened, thus lacking key information only a 3 dimensional skull could give them. </p><p>This latest finding, detailed in a paper published last week in the journal <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(20)31150-7" target="_blank" rel="noopener noreferrer">Current Biology</a>, is 3-D enough to contain all those revealing details. Including the befuddling facial features that titanosaur babies apparently wore in their first days of life. </p>
Inside the egg<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzYwNDA5OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNDM3NTYwOH0.AfJaAsSEiTO1fy4URsrFuOrJLDrMaoyVKBzSVW9n7wI/img.jpg?width=1200&coordinates=0%2C15%2C0%2C15&height=800" id="f81d5" class="rm-shortcode" data-rm-shortcode-id="173a70baad139b140326acfb73cd297b" data-rm-shortcode-name="rebelmouse-image" data-width="1200" data-height="800" />
Kundrát et al., Current Biology, 2020<p>The research team used synchrotron microtomography, a cutting edge imaging technology, to view the embryo's bones, teeth, and soft tissues, like the calcified remains of the baby's brain case and jaw muscles.</p><p>While the prehistoric long-necked beasts have always been depicted in their adult forms, the high tech images reveal that the babies actually had some unusual physical traits. They had binocularly focused vision in the front of the head rather than on each side, retracted openings on their snout, and a single horn in the front of their head. The researchers have speculated that the horn may have helped them crack out of their shell at birth and assisted these vulnerable newborns in defending themselves. There is currently no evidence of parental care in this dinosaur species, so the baby titanosaurus would have likely been fending for itself for food and protection.</p><p>"You could call it a unicorn baby dinosaur, because it has a single horn on its head. But unlike the mythical unicorn, where the horn is on the forehead, this dinosaur has a small bumpy horn at the tip of its snout," University of Edinburgh vertebrate paleontologist Stephen Brusatte, who wasn't involved in the new study, told the New York Times. "This little embryo is one of the cutest dinosaurs I've seen, and at the same time, one of the weirdest looking."</p><p>As the dinosaur matured, its head and face would have morphed into the features we imagine them as today; their vision likely changed as their eyes shifted laterally to the sides of the head. Their snout and face may have grown faster than their braincase to get rid of the horn. This is all speculation, of course, as more examples are needed. </p><p>"We expect that the specimen will become one of the most important fossils in the study of reproduction and development of the gigantic quadrupedal dinosaurs," said Martin Kundrát in an email to CNN, study author and head of the PaleoBioImaging Lab at Pavol Jozef Šafárik University in Slovakia.</p><p>Though the researchers acknowledge that it is possible that they stumbled upon an entirely new species, the embryo is the most similar to Tapuiasaurus — a titanosaurus dinosaur that lived in Brazil between 66 million and 100.5 million years ago. </p>
"You dream about these kinds of moments when you're a kid," said lead paleontologist David Schmidt.
- The triceratops skull was first discovered in 2019, but was excavated over the summer of 2020.
- It was discovered in the South Dakota Badlands, an area where the Triceratops roamed some 66 million years ago.
- Studying dinosaurs helps scientists better understand the evolution of all life on Earth.
Credit: David Schmidt / Westminster College<p style="margin-left: 20px;">"We had to be really careful," Schmidt told St. Louis Public Radio. "We couldn't disturb anything at all, because at that point, it was under law enforcement investigation. They were telling us, 'Don't even make footprints,' and I was thinking, 'How are we supposed to do that?'"</p><p>Another difficulty was the mammoth size of the skull: about 7 feet long and more than 3,000 pounds. (For context, the largest triceratops skull ever unearthed was about <a href="https://www.tandfonline.com/doi/abs/10.1080/02724634.2010.483632" target="_blank">8.2 feet long</a>.) The skull of Schmidt's dinosaur was likely a <em>Triceratops prorsus, </em>one of two species of triceratops that roamed what's now North America about 66 million years ago.</p>
Credit: David Schmidt / Westminster College<p>The triceratops was an herbivore, but it was also a favorite meal of the T<em>yrannosaurus rex</em>. That probably explains why the Dakotas contain many scattered triceratops bone fragments, and, less commonly, complete bones and skulls. In summer 2019, for example, a separate team on a dig in North Dakota made <a href="https://www.nytimes.com/2019/07/26/science/triceratops-skull-65-million-years-old.html" target="_blank">headlines</a> after unearthing a complete triceratops skull that measured five feet in length.</p><p>Michael Kjelland, a biology professor who participated in that excavation, said digging up the dinosaur was like completing a "multi-piece, 3-D jigsaw puzzle" that required "engineering that rivaled SpaceX," he jokingly told the <a href="https://www.nytimes.com/2019/07/26/science/triceratops-skull-65-million-years-old.html" target="_blank">New York Times</a>.</p>
Morrison Formation in Colorado
James St. John via Flickr
|Credit: Nobu Tamura/Wikimedia Commons|
Fossils depicting animals in action are very rare.
- A fossil of a prehistoric ant hunting has recently been discovered.
- Fossilization is rare, so depictions of activities like hunting are hard to come by.
- Other fossils show us how dinosaurs hunted, fought, and died.
The rarity of action shot fossils<p>Fossilization of any kind is infrequent. While the things that must go right for it to happen vary on the method, a typical dinosaur fossil would have to be buried in minerals conducive to fossilization before too much of it decays or is scattered <a href="http://geology.isu.edu/Alamo/fossils/process_fossilization.php#:~:text=Fossilization%20is%20the%20process%20by,years%20are%20preserved%20as%20fossils." target="_blank">away</a>.</p><p>The odds of this happening are low. The odds of this happening with two animals that were fighting at the time of their death are even lower. However, improbability is not the same as impossibility, and several other fantastic examples of ancient predators engaged in life and death struggles with their prey have been preserved.</p>
The “Fighting Dinosaurs” of Mongolia<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzU2OTg5NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMjAzMjI2OH0.w7N0c7sarqd7SrntZzhFGBj4ukTN4AYVeCK_cV2R_Iw/img.jpg?width=1245&coordinates=0%2C0%2C0%2C0&height=700" id="e82f1" class="rm-shortcode" data-rm-shortcode-id="d9454690c662851272ae7d53df5718bf" data-rm-shortcode-name="rebelmouse-image" alt="Two dinosaurs skeletons fighting" data-width="1245" data-height="700" />
By Yuya Tamai from Gifu, Japan - 2014-03-25 13.04.52, CC BY 2.0<p>One of the more famous fossils of all time is a depiction of a velociraptor fighting a protoceratops. In the above picture, you can see the raptor's slashing claw where the neck of the protoceratops once was and the raptor's forearm caught in the beak of its <a href="https://www.amnh.org/exhibitions/fighting-dinos/the-fighting-dinosaurs" target="_blank">prey</a>.</p><p>Discovered by a Polish-Mongolian team in the seventies, these remains are thought to have been preserved by the rapid collapse of a sand dune onto the battling animals, or by their rapid burial in a sandstorm.</p><p>Not only is this fantastic to look at, but it provides us with evidence about how these species of dinosaur behaved that more typical remains cannot offer. For example, while it was commonly supposed that a velociraptor's claw was used to disembowel prey, this scene demonstrates that it was likely used elsewhere. Some have even gone so far as to suggest it wasn't designed to create slashing wounds at all, but instead was used to grab <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1617199/" target="_blank">prey</a>. </p>
Montana’s Dueling Dinos<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="03301e661e226e7d9ea96357122fcee8"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/xwpugYXB1RA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>The subject of an extended ownership debate that was only recently <a href="https://www.sciencemag.org/news/2020/05/court-rules-dueling-dinos-belong-landowners-win-science" target="_blank">settled</a>, this fossil has yet to be seen by the public and has already been built into the stuff of legend. </p><p>It depicts a Tyrannosaurs-esque predator locked in combat with a potentially unknown member of the ceratopidae family (that's the group that has horns on their faces, like the eternally loved triceratops). The extended court cases around the ownership of the remains haven't been able to eclipse the find's incredible nature.</p><p>In addition to depicting predation, the Tyrannosaurus fossil is nearly <a href="https://www.sciencemag.org/news/2020/05/court-rules-dueling-dinos-belong-landowners-win-science" target="_blank">complete</a>, making it one of about a dozen near-complete T-Rex fossils. </p><p>Clayton Phipps, the discoverer of the fossils, further explained how incredible the find was to <a href="https://www.smithsonianmag.com/science-nature/public-ever-see-dueling-dinosaurs-180963676/" target="_blank" rel="noopener noreferrer dofollow">Smithsonian Magazine</a>: "There's an entire skin envelope around both dinosaurs," Phipps says. "They're basically mummies. There could be soft tissue inside."</p><p>Others are less convinced of the importance of this discovery. <a href="https://en.wikipedia.org/wiki/Jack_Horner_(paleontologist)" target="_blank" rel="dofollow">John Horner</a>, the paleontologist who dug up the famous T-Rex known as "Sue," dismissed the find as "scientifically useless" due to the lack of data collected at the site by the people who dug it <a href="https://www.smithsonianmag.com/science-nature/public-ever-see-dueling-dinosaurs-180963676/" target="_blank" rel="noopener noreferrer dofollow">up</a>. </p><p>Despite his objections, interest in the fossil remains high, likely due to the aforementioned rarity of such a depiction by a fossil. </p>
A recent analysis of a 76-million-year-old Centrosaurus apertus fibula confirmed that dinosaurs suffered from cancer, too.
- The fibula was originally discovered in 1989, though at the time scientists believed the damaged bone had been fractured.
- After reanalyzing the bone, and comparing it with fibulas from a human and another dinosaur, a team of scientists confirmed that the dinosaur suffered from the bone cancer osteosarcoma.
- The study shows how modern techniques can help scientists learn about the ancient origins of diseases.
Centrosaurus apertus fibula
Royal Ontario Museum<p>In the recent study, the team used a combination of techniques to analyze the fibula, including taking CT scans, casting the bone and studying thin slices of it under a microscope. The analysis suggested that the dinosaur likely suffered from osteosarcoma, a type of bone cancer that affects modern humans, typically young adults.</p><p>For further evidence, the team compared the damaged fibula to a healthy fibula from a dinosaur of the same species, and also to a fibula that belonged to a 19-year-old human who suffered from osteosarcoma. Both comparisons supported the osteosarcoma diagnosis.</p>
Evans et al.<p style="margin-left: 20px;">"The shin bone shows aggressive cancer at an advanced stage," Evans said in a <a href="https://www.rom.on.ca/en/about-us/newsroom/press-releases/rare-malignant-cancer-diagnosed-in-a-dinosaur" target="_blank">press release</a>. "The cancer would have had crippling effects on the individual and made it very vulnerable to the formidable tyrannosaur predators of the time."</p><p style="margin-left: 20px;">"The fact that this plant-eating dinosaur lived in a large, protective herd may have allowed it to survive longer than it normally would have with such a devastating disease."</p><p>The fossilized fibula was originally unearthed in a bonebed alongside the remains of dozens of other <em>Centrosaurus </em><em>apertus</em>, suggesting the dinosaur didn't die from cancer, but from a flood that swept it away with its herd.</p>
Dinosaur fibula; the tumor mass is depicted in yellow.
Royal Ontario Museum/McMaster University<p>The new study highlights how modern techniques can help scientists learn more about the evolutionary origins of modern diseases, like cancer. It also shows that dinosaurs suffered through some of the same terrestrial afflictions humans face today.</p><p style="margin-left: 20px;">"Dinosaurs can seem like mythical creatures, but they were living, breathing animals that suffered through horrible injuries and diseases," Evans said, "and this discovery certainly makes them more real and helps bring them to life in that respect."</p>