Earlier this month, a study in the journal Science tried to put to bed for good the question of dinosaur extinction: It was an impact from space, not large-scale volcanic activity, that wiped them out 65 million years ago, the study argued. That’s all well and good for the dinosaur’s end, but what about their beginning?
This week in the Proceedings of the National Academy of Sciences, paleontologists say they’ve studied the period about 200 million years ago when dinosaurs first came to power, and found that while catastrophic volcanic activity may not explain dinosaur extinction, it could have explained why dinosaurs’ competitors disappeared and the terrible lizards took over the planet.
Around the time of dino emergence, the continents were all locked up in the supercontinent Pangaea. As it pulled apart, researchers say the seismic activity gave rise to hundreds of thousands of years of volcanic activity, creating lava fields on the surface of the Earth the size of the continental United States. For this study, Jessica Whiteside and colleagues surveyed wood remnants, wax from ancient leaves, and whatever else they could extract from the volcanic flow’s remains to reconstruct what was happening in the climate of this period.
The scientists examined how two different isotopes (or forms) of carbon fluctuated during these volcanic eruptions. They found that the “heavy” form of carbon was depleted relative to the “light” form. They say this reflects disturbances in the carbon cycle at this time, including a spike in atmospheric carbon dioxide (CO2) and aerosols (fine solid particles) [BBC News].
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Will we ever get a solid answer on what killed the dinosaurs? According to a new “K-T Boundary Dream Team” comprising of 41 international experts, including geophysicists and paleontologists, yes, the question has been settled: An asteroid is indeed to blame.
For years, scientists have argued over different theories of what killed the dinos–including one hypothesis that has gained ground recently, which suggests that massive volcanic activity in India’s Deccan Traps wiped them out 65 million years ago. However, the latest expert panel stuck to the asteroid theory, saying a massive impact wiped out the dinos and more than half of the Earth’s other species. The panel’s review was published in the journal Science.
After studying all the available data on the Cretaceous-Tertiary (K-T) mass extinction, the panel concluded that the catastrophic event was caused by a 6-mile-wide asteroid that struck Earth at an angle of 90 degrees and a speed of about 12.4 miles per second – about 20 times faster than a speeding bullet [Guardian]. The asteroid hit Chicxulub, Mexico, with a force one billion times more powerful than the atomic bomb at Hiroshima [Science Daily News].
The impact of the crash would have triggered large scale fires, landslides, earthquakes that measured 10 on the Richter scale, and subsequent tsunamis, scientists said. Debris loosened by the impact would have shrouded the planet, clouding the skies, causing a global darkness, and “killing off many species that couldn’t adapt to this hellish environment” [Science Daily News], according to study coauthor Joanna Morgan.
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In this week’s Nature, researchers say they’ve analyzed a near-complete skeleton of one of the closest relatives to early dinosaurs, a silesaur called Asilisaurus. The fossil is more than 240 million years old, which is ten million years older than the earliest known fossils of true dinosaurs. The finding of this dino relative therefore suggests that dinosaurs emerged earlier than we previously believed, and it throws another surprise into the debate over their origins.
From the remains of 14 different individuals, the scientists managed to piece together what a whole skeleton looked like. However, the finished product didn’t look quite like they expected. After studying the bones for 3 years, the team concludes that Asilisaurus was about the size of a Labrador retriever. The animal walked on four legs, and the shape of its teeth suggests that it ate plants and maybe a little meat.[ScienceNOW]. That conflicted with the expectation of study coauthor Randy Irmis, who said the team would’ve thought small carnivores, and not mostly plant eaters walking on four legs, were the closest relatives to the dinosaurs.
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Take a good look: according to a new study in PLoS Biology, what you see in this image is a snake about to prey on dinosaur eggs, a 67-million-year-old scene frozen in time and finally discovered. It’s the first time that a snake has been seen eating a dinosaur. The snake is that bit of bones on the left, lead researcher Jeff Wilson says. The egg in the top right contains a tiny titanosaur, one of largest dinosaur groups to ever walk the Earth.
“The snake (Sanajeh indicus) probably lived around the nesting ground and preyed upon hatchlings. They all died instantly when they were covered by a big pulse of sediment from a nearby hill loosened by a storm,” says Wilson [New Scientist]. Wilson guesses that a storm or some other malady might have led the enormous adult dinos to leave the nest, opening the door for the snake to slither in, wait for the baby dinos to hatch, and snack on them. But it never got the chance.
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Dinosaurs and explosives—science stories don’t get much cooler than this.
Researchers in Utah have excavated two complete and two partial skulls of a dino called Abydosaurus mcintoshi, a 105-million-year-old sauropod, which the scientists think might have descended from the brachiosaurus family. “It is amazing. You can hold the skull in your hands and look into the eyes of something that lived a very long time ago” [USA Today], says paleontologist Brooks Britt, co-author of the study that appeared in the journal Naturwissenschaften.
Click through the photo gallery for more pictures from the dig, and for the whole story.
Image: Brigham Young University
Last week, a study found that an early dinosaur had a red mohawk and striped tail, one of the first pieces of solid evidence regarding dinosaur coloration. But a new study forthcoming in Science goes one step further, mapping in full 3D the strange plumage of the earliest-known feathered dinosaur, Anchiornis huxleyi.
Richard O. Prum, leader of the new study, was among the first to document that pigment-giving structures called melanosomes could survive fossilized for millions of years. The shape and arrangement of melanosomes help produce the color of feathers, so the scientists were able to get clues about the color of fossil feathers from their melanosomes alone [The New York Times]. British and Chinese scientists used this technique to release last week’s color study of the 125-million-year-old Sinosauropteryx, and Prum’s team applied it to the 150-million-year-old Anchiornis.
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As much as paleontologists have sorted out about the dinosaurs, one of the main aspects of their appearance—what color they were—has remained mysterious. But in a new Nature study, a team of British and Chinese scientists report that they found a way to unlock the color patters of one of the earliest feathery dinosaurs—it had a red mohawk, they say, with a red and white striped tail.
The dino in question is called Sinosauropteryx, which lived about 125 million years ago. Looking at fossils found in China, the team led by Mike Benton found what they think are the remains of feathers. And they found something inside the feathers that matches modern birds: melanosomes. These structures provide the melanin pigment in bird feathers (and human hair), and what color they are depends on the shape. “A ginger-haired person would have more spherical melanosomes, and a black-haired or grey-haired person would have more of the sausage-shaped structures,” said Professor Benton [BBC News].
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Until or unless we can create a Jurassic Park and build dinosaurs from DNA, the best way to study them may be to build dino models using materials like balsa wood, carbon fiber, and rubber bands.
That’s what a team did for a new study in the Proceedings of the National Academies of Sciences. To figure out how the 120-million-year-old winged dinosaur Microraptor gui took to the skies, the researchers used a well-preserved fossil to build their own. “We went back and forth. We thought, maybe we’ll do 3-D graphics and it’ll look really cool. But it’s more accurate to do the modeling directly from the specimen,” said Dave Burnham, a paleontologist at the University of Kansas [Wired.com].
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Earlier this month DISCOVER covered the 213-million-year-old fossils of the theropod Tawa hallae, a dinosaur ancestor that could show how early dinos spread around the world. Now, in a study (in press) in the Proceedings of the National Academy of Sciences, another research team has uncovered a surprise in the bones of a theropod from almost 100 million years later. By that time, these creatures may have adopted a clever new weapon: venom.
Sinornithosaurus lived 125 million years ago in what’s now China, and while it might have been covered in feathers (and the size of a turkey), the researchers say it attacked like modern rear-fanged snakes. Rear-fanged snakes don’t inject venom. Instead, the toxin flows down a telltale groove in a fang’s surface and into the bite wound, inducing a state of shock [National Geographic].
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Sixty-five million years ago—we know when the dinosaur story ends. But the beginning of the dinosaur age is hazier, due to the small number of distinct fossils with which to set a time frame. But now scientists have turned up fossils in New Mexico of an early dinosaur ancestor, they report tomorrow in the journal Science, one that points to South America as the possible place of dinosaur origin.
The feathered beast, named Tawa hallae, was the size of a large dog and sported a long neck and tail, a slender snout, and sharp, curved teeth to catch and kill its prey [The Guardian]. Tawa hallae is an early theropod, meaning it is related to birds and the mighty T. Rex.
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You’d think something with as much awesome power as the talons on birds of prey would be among the better-understood appendages in the animal kingdom. Not so, say the authors of a new in PLoS One, but they’ve rectified the situation by analyzing 24 different birds to reveal the evolution and use of talons by the owl, osprey, falcon, and more.
They describe how accipitrids, which include hawks and eagles, have two giant talons on their first and second toes [as in pictures A and B]. These give them a secure grip on struggling game that they like to eat alive, “so long as it does not protest too vigorously. In this prolonged and bloody scenario, prey eventually succumb to massive blood loss or organ failure, incurred during dismemberment” [Wired.com].
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A thrilling set of ancient crocodile fossils have been unearthed in northern Africa. A “saber-toothed cat in armor” and a pancake-shaped predator are among the strange crocodile cousins whose bones have been found beneath the windswept dunes of the Sahara, archaeologists say [National Geographic News].
At a news conference organized by the National Geographic Society, which sponsored the research, scientists announced that the fossils represent 5 species; 3 new species and 2 that were previously known. These ancient croc ancestors, known as crocodilyforms, are unlike any crocodiles encountered in the Northern Hemisphere, according to the research team. Their findings are detailed in the journal ZooKeys.
The crocs were spectacularly diverse, and included a species that ate dinosaurs, two that grew up to 20 feet long, and two that had long legs for quick movement on land but also had long tails for swimming. The three new species are:
• BoarCroc (Kaprosuchus saharicus), a 20-foot meat-eater. It used its snout for ramming and three sets of dagger-shaped fangs for slicing dinosaurs it ate.
• PancakeCroc (Laganosuchus thaumastos): a 20-foot-long, squat fish-eater with a 3-foot long flat head with spike-shaped teeth.
• RatCroc (Araripesuchus rattoides), a 3-foot-long plant and grub eater with buckteeth used for digging [Chicago Sun-Times].
The two previously known species are nicknamed DuckCroc, a three-foot long, long-legged croc that feasted on fish and frogs, and DogCroc, another small and lanky croc that mostly ate plants and grubs.
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The world domination achieved by such fearsome bipedal dinosaurs as the T. rex may have been a result of their warm-blooded biology, according to new research. For decades, scientists assumed that because dinosaurs resembled lizards, they were cold-blooded as well, their internal temperature rising and falling with the outside world. However, birds are warm-blooded, and the fact that birds seem to be descended from dinosaurs raises the question of whether their ancestors were as well [LiveScience]. The new study, published in the journal PLoS ONE, examined the anatomy of 14 species of bipedal dinosaurs, and argues that many of them needed more energy to power their massive leg muscles than a cold-blooded metabolism could provide.
Lead researcher Herman Pontzer based his findings on the estimated amount of energy dinosaurs must have expended moving about. Recent research by Dr Pontzer has shown that the energy cost of walking and running is strongly associated with leg length. Hip height – the distance from the hip joint to the ground – can predict the observed cost of locomotion with 98 per cent accuracy for a wide range of land animals [Telegraph]. The research team also used measurements of fossilized leg bones to determine the leg muscle mass of each species, and found that the muscles would have required a great deal of energy during walking and running.
The dinosaurs would have benefited from a warm-blooded metabolism, Pontzer says, because they could have been agile and active even when the temperature dipped, and could have therefore spread through areas with colder climates. But there would also have been a downside: Maintaining a stable internal temperature … costs a lot of energy and requires the animals to feed more regularly [The Guardian]. At any rate, the new results aren’t likely to convince paleontologists who aren’t in the warm-blooded camp, and you can expect the debate to continue.
Related Content:
80beats: Miniature T. Rex Was a Man-Sized Monster
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DISCOVER: Distinctive Dinosaur Death Throes
DISCOVER: How to Build a T. Rex
Image: PLoS ONE / Herman Pontzer, et al.
Could the Chicago Field Museum’s mighty Tyrannosaurus Rex, a dino named Sue, have been toppled by a lowly parasite? According to a recent study in the journal PLoS ONE, a microbe commonly found in pigeons may be responsible for holes in the dinosaur‘s mandible, holes that were previously thought to be bite marks. Paleontologists compared a similar infection in a modern predatory bird to the T-Rex holes and found surprising similarities.
The researchers think the parasite, a protozoan named Trichomonas gallinae, settled in the back of Sue’s throat, and in nine other Tyrannosaurs … studied with similar holes. The parasite caused inflammation that eventually damaged the jawbone [Los Angeles Times], first forming lesions and then eroding the bone away. The inflammation would have choked off the dino’s esophagus, they say, eventually starving the T. Rex to death.
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A feathered dinosaur unearthed in a Chinese quarry has added another solid piece of evidence to the theory that birds descended from dinosaurs. The newly uncovered fossil of the species Anchiornis huxleyi dates from the Late Jurassic period, 151-161 million years ago, and therefore predates the earliest known bird, the Archaeopteryx. Paleontologists say this represents the final proof that dinosaurs were ancestral to birds. “Drawing the tree of life, it’s fairly obvious that feathers arose before Archaeopteryx appears in the fossil record” [BBC News], says paleontologist Michael Benton.
The creature, described in a paper [pdf] in Nature, was covered in the short feathers known as “dino-fuzz,” and had longer feathers on both its forelimbs and its back legs that formed primitive wings. The four-winged dinosaurs also had feathers on their feet and wing-like attachments on the arms and legs. But they could probably only glide, as their plumage was insufficient for powered flight [Nature News].
Related Content:
80beats: New Fossil Suggests That Fuzzy Dinosaurs Were Plentiful
80beats: To Attract Mates, This Dino May Have Shaken a Tail Feather
80beats: “Bizarre” and Fluffy Dino May Have Used Feathers to Attract Mates
Image: Zhao Chuang, Xing Lida. An artist’s rendering of Anchiornis huxleyi.
