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CNN
11-04-2025
- Science
- CNN
Were dinosaurs headed for extinction even before massive asteroid strike? Scientists offer new clues
It's a long-standing debate in paleontology: Were dinosaurs thriving when an asteroid hit Earth one fateful spring day 66 million years ago, or were they already on their way out, and the space rock delivered a final, devastating blow? To find answers, a team of researchers studied North America's fossil record, focusing on the 18 million years before the mass extinction at the end of the Cretaceous period. The new analysis, published Tuesday in the journal Current Biology, adds to a growing body of evidence that the dinosaurs were doing just fine before the asteroid's deadly impact. However, at face value, the fossils available for study from this time — more than 8,000 — suggest the number of dinosaur species peaked about 75 million years ago and then declined in the 9 million years leading up to the asteroid strike. 'It comes down to the fossil record and its fidelity, or its quality. And so there's been an awareness since the 1970s that the fossil record is not accurate, but it is a biased reflection in the past,' said lead study author Chris Dean, a research fellow in paleontology at University College London. 'It's only in very recent years that we've started to see the full extent of (the bias issue), when using these large databases of fossil occurrences,' he said. To understand better what was going on at the time of the dinosaurs' demise, Dean and his colleagues turned to a statistical approach called occupancy modeling to estimate the probability of a dinosaur being present at a site. Used in present-day ecology and conservation, occupancy modeling aims to account for the fact that a species may be overlooked or not detected even when present in a particular area. This study marks the first time the approach has been used to look at dinosaurs and over a large scale, Dean said. 'Applying a new technique is really hard,' Dean noted. 'I don't think it will be the last word. I'm sure there's a lot more to be said.' For the new study, the researchers looked at four main dinosaur families: Ankylosauridae (armored plant-eating dinosaurs such as the club-tailed Ankylosaurus), Ceratopsidae (large three-horned herbivores including Triceratops), Hadrosauridae (duck-billed dinosaurs), and Tyrannosauridae (carnivores such as Tyrannosaurus rex). 'We looked at these bigger groupings so we could have more data, effectively,' Dean said. 'We gridded up North America into a big spatial grid (and determined) the places where we can find fossils, (the places where we) have physically found fossils and how many times people have gone to look for fossils (in these places).' The information was fed into a computer model, and Dean and his colleagues compared the physical fossil record with that proposed by the model and found a mismatch. The model suggested that, during the 18 million-year time period in question, the proportion of land the four dinosaur clades likely occupied remained constant overall, suggesting their potential habitat area remained stable, and the risk of extinction stayed low. One of the factors that could have clouded the true diversity patterns of dinosaurs was the lack of rock exposed at the Earth's surface during that window of time — and thus available for fossil hunters today to scrutinize. 'In this study, we show that this apparent decline is more likely a result of a reduced sampling window, caused by geological changes in these terminal Mesozoic fossil-bearing layers — driven by processes such as tectonics, mountain uplift, and sea-level retreat — rather than genuine fluctuations in biodiversity,' said study coauthor Alfio Alessandro Chiarenza, a Royal Society Newton International Fellow at University College London's department of Earth sciences, in a statement. 'Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic,' Chiarenza said. 'If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds.' The study helped to highlight what biases may affect scientists' understanding of the true pattern of dinosaur diversity leading up to the extinction event, said Darla Zelenitsky, a paleontologist at the University of Calgary in Alberta who wasn't involved in the research. 'Because of the nature of the rock record, (paleontologists have) found it was more difficult to detect dinosaurs and thus understand their diversity patterns in that window of time just before the mass extinction,' she said. 'It certainly makes sense as we know there are biases related to the rock record that can obscure true biological patterns. The more rock that is exposed at the surface (today), the better our chance of finding dinosaurs in that rock, which in turn leads to a better understanding of their diversity patterns.' Mike Benton, a professor of vertebrate paleontology at the UK's University of Bristol, called the paper 'thorough and detailed' but said it doesn't prove there was no reduction in dinosaur diversity ahead of the extinction event. Benton's work has suggested that dinosaurs were in decline before the asteroid wiped them out. He wasn't involved in the new study. 'The current paper suggests that the 'reduction' can be explained as a statistical artefact,' Benton said via email. 'What it shows is … simply that the reduction could be real or could be explained by reduced sampling, in my opinion.'
Yahoo
11-04-2025
- Science
- Yahoo
Were dinosaurs headed for extinction even before massive asteroid strike? Scientists offer new clues
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. It's a long-standing debate in paleontology: Were dinosaurs thriving when an asteroid hit Earth one fateful spring day 66 million years ago, or were they already on their way out, and the space rock delivered a final, devastating blow? To find answers, a team of researchers studied North America's fossil record, focusing on the 18 million years before the mass extinction at the end of the Cretaceous period. The new analysis, published Tuesday in the journal Current Biology, adds to a growing body of evidence that the dinosaurs were doing just fine before the asteroid's deadly impact. However, at face value, the fossils available for study from this time — more than 8,000 — suggest the number of dinosaur species peaked about 75 million years ago and then declined in the 9 million years leading up to the asteroid strike. 'It comes down to the fossil record and its fidelity, or its quality. And so there's been an awareness since the 1970s that the fossil record is not accurate, but it is a biased reflection in the past,' said lead study author Chris Dean, a research fellow in paleontology at University College London. 'It's only in very recent years that we've started to see the full extent of (the bias issue), when using these large databases of fossil occurrences,' he said. To understand better what was going on at the time of the dinosaurs' demise, Dean and his colleagues turned to a statistical approach called occupancy modeling to estimate the probability of a dinosaur being present at a site. Used in present-day ecology and conservation, occupancy modeling aims to account for the fact that a species may be overlooked or not detected even when present in a particular area. This study marks the first time the approach has been used to look at dinosaurs and over a large scale, Dean said. 'Applying a new technique is really hard,' Dean noted. 'I don't think it will be the last word. I'm sure there's a lot more to be said.' For the new study, the researchers looked at four main dinosaur families: Ankylosauridae (armored plant-eating dinosaurs such as the club-tailed Ankylosaurus), Ceratopsidae (large three-horned herbivores including Triceratops), Hadrosauridae (duck-billed dinosaurs), and Tyrannosauridae (carnivores such as Tyrannosaurus rex). 'We looked at these bigger groupings so we could have more data, effectively,' Dean said. 'We gridded up North America into a big spatial grid (and determined) the places where we can find fossils, (the places where we) have physically found fossils and how many times people have gone to look for fossils (in these places).' The information was fed into a computer model, and Dean and his colleagues compared the physical fossil record with that proposed by the model and found a mismatch. The model suggested that, during the 18 million-year time period in question, the proportion of land the four dinosaur clades likely occupied remained constant overall, suggesting their potential habitat area remained stable, and the risk of extinction stayed low. One of the factors that could have clouded the true diversity patterns of dinosaurs was the lack of rock exposed at the Earth's surface during that window of time — and thus available for fossil hunters today to scrutinize. 'In this study, we show that this apparent decline is more likely a result of a reduced sampling window, caused by geological changes in these terminal Mesozoic fossil-bearing layers — driven by processes such as tectonics, mountain uplift, and sea-level retreat — rather than genuine fluctuations in biodiversity,' said study coauthor Alfio Alessandro Chiarenza, a Royal Society Newton International Fellow at University College London's department of Earth sciences, in a statement. 'Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic,' Chiarenza said. 'If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds.' The study helped to highlight what biases may affect scientists' understanding of the true pattern of dinosaur diversity leading up to the extinction event, said Darla Zelenitsky, a paleontologist at the University of Calgary in Alberta who wasn't involved in the research. 'Because of the nature of the rock record, (paleontologists have) found it was more difficult to detect dinosaurs and thus understand their diversity patterns in that window of time just before the mass extinction,' she said. 'It certainly makes sense as we know there are biases related to the rock record that can obscure true biological patterns. The more rock that is exposed at the surface (today), the better our chance of finding dinosaurs in that rock, which in turn leads to a better understanding of their diversity patterns.' Mike Benton, a professor of vertebrate paleontology at the UK's University of Bristol, called the paper 'thorough and detailed' but said it doesn't prove there was no reduction in dinosaur diversity ahead of the extinction event. Benton's work has suggested that dinosaurs were in decline before the asteroid wiped them out. He wasn't involved in the new study. 'The current paper suggests that the 'reduction' can be explained as a statistical artefact,' Benton said via email. 'What it shows is … simply that the reduction could be real or could be explained by reduced sampling, in my opinion.'
CNN
11-04-2025
- Science
- CNN
Were dinosaurs headed for extinction even before massive asteroid strike? Scientists offer new clues
It's a long-standing debate in paleontology: Were dinosaurs thriving when an asteroid hit Earth one fateful spring day 66 million years ago, or were they already on their way out, and the space rock delivered a final, devastating blow? To find answers, a team of researchers studied North America's fossil record, focusing on the 18 million years before the mass extinction at the end of the Cretaceous period. The new analysis, published Tuesday in the journal Current Biology, adds to a growing body of evidence that the dinosaurs were doing just fine before the asteroid's deadly impact. However, at face value, the fossils available for study from this time — more than 8,000 — suggest the number of dinosaur species peaked about 75 million years ago and then declined in the 9 million years leading up to the asteroid strike. 'It comes down to the fossil record and its fidelity, or its quality. And so there's been an awareness since the 1970s that the fossil record is not accurate, but it is a biased reflection in the past,' said lead study author Chris Dean, a research fellow in paleontology at University College London. 'It's only in very recent years that we've started to see the full extent of (the bias issue), when using these large databases of fossil occurrences,' he said. To understand better what was going on at the time of the dinosaurs' demise, Dean and his colleagues turned to a statistical approach called occupancy modeling to estimate the probability of a dinosaur being present at a site. Used in present-day ecology and conservation, occupancy modeling aims to account for the fact that a species may be overlooked or not detected even when present in a particular area. This study marks the first time the approach has been used to look at dinosaurs and over a large scale, Dean said. 'Applying a new technique is really hard,' Dean noted. 'I don't think it will be the last word. I'm sure there's a lot more to be said.' For the new study, the researchers looked at four main dinosaur families: Ankylosauridae (armored plant-eating dinosaurs such as the club-tailed Ankylosaurus), Ceratopsidae (large three-horned herbivores including Triceratops), Hadrosauridae (duck-billed dinosaurs), and Tyrannosauridae (carnivores such as Tyrannosaurus rex). 'We looked at these bigger groupings so we could have more data, effectively,' Dean said. 'We gridded up North America into a big spatial grid (and determined) the places where we can find fossils, (the places where we) have physically found fossils and how many times people have gone to look for fossils (in these places).' The information was fed into a computer model, and Dean and his colleagues compared the physical fossil record with that proposed by the model and found a mismatch. The model suggested that, during the 18 million-year time period in question, the proportion of land the four dinosaur clades likely occupied remained constant overall, suggesting their potential habitat area remained stable, and the risk of extinction stayed low. One of the factors that could have clouded the true diversity patterns of dinosaurs was the lack of rock exposed at the Earth's surface during that window of time — and thus available for fossil hunters today to scrutinize. 'In this study, we show that this apparent decline is more likely a result of a reduced sampling window, caused by geological changes in these terminal Mesozoic fossil-bearing layers — driven by processes such as tectonics, mountain uplift, and sea-level retreat — rather than genuine fluctuations in biodiversity,' said study coauthor Alfio Alessandro Chiarenza, a Royal Society Newton International Fellow at University College London's department of Earth sciences, in a statement. 'Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic,' Chiarenza said. 'If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds.' The study helped to highlight what biases may affect scientists' understanding of the true pattern of dinosaur diversity leading up to the extinction event, said Darla Zelenitsky, a paleontologist at the University of Calgary in Alberta who wasn't involved in the research. 'Because of the nature of the rock record, (paleontologists have) found it was more difficult to detect dinosaurs and thus understand their diversity patterns in that window of time just before the mass extinction,' she said. 'It certainly makes sense as we know there are biases related to the rock record that can obscure true biological patterns. The more rock that is exposed at the surface (today), the better our chance of finding dinosaurs in that rock, which in turn leads to a better understanding of their diversity patterns.' Mike Benton, a professor of vertebrate paleontology at the UK's University of Bristol, called the paper 'thorough and detailed' but said it doesn't prove there was no reduction in dinosaur diversity ahead of the extinction event. Benton's work has suggested that dinosaurs were in decline before the asteroid wiped them out. He wasn't involved in the new study. 'The current paper suggests that the 'reduction' can be explained as a statistical artefact,' Benton said via email. 'What it shows is … simply that the reduction could be real or could be explained by reduced sampling, in my opinion.'
CNN
11-04-2025
- Science
- CNN
Were dinosaurs headed for extinction even before massive asteroid strike? Scientists offer new clues
It's a long-standing debate in paleontology: Were dinosaurs thriving when an asteroid hit Earth one fateful spring day 66 million years ago, or were they already on their way out, and the space rock delivered a final, devastating blow? To find answers, a team of researchers studied North America's fossil record, focusing on the 18 million years before the mass extinction at the end of the Cretaceous period. The new analysis, published Tuesday in the journal Current Biology, adds to a growing body of evidence that the dinosaurs were doing just fine before the asteroid's deadly impact. However, at face value, the fossils available for study from this time — more than 8,000 — suggest the number of dinosaur species peaked about 75 million years ago and then declined in the 9 million years leading up to the asteroid strike. 'It comes down to the fossil record and its fidelity, or its quality. And so there's been an awareness since the 1970s that the fossil record is not accurate, but it is a biased reflection in the past,' said lead study author Chris Dean, a research fellow in paleontology at University College London. 'It's only in very recent years that we've started to see the full extent of (the bias issue), when using these large databases of fossil occurrences,' he said. To understand better what was going on at the time of the dinosaurs' demise, Dean and his colleagues turned to a statistical approach called occupancy modeling to estimate the probability of a dinosaur being present at a site. Used in present-day ecology and conservation, occupancy modeling aims to account for the fact that a species may be overlooked or not detected even when present in a particular area. This study marks the first time the approach has been used to look at dinosaurs and over a large scale, Dean said. 'Applying a new technique is really hard,' Dean noted. 'I don't think it will be the last word. I'm sure there's a lot more to be said.' For the new study, the researchers looked at four main dinosaur families: Ankylosauridae (armored plant-eating dinosaurs such as the club-tailed Ankylosaurus), Ceratopsidae (large three-horned herbivores including Triceratops), Hadrosauridae (duck-billed dinosaurs), and Tyrannosauridae (carnivores such as Tyrannosaurus rex). 'We looked at these bigger groupings so we could have more data, effectively,' Dean said. 'We gridded up North America into a big spatial grid (and determined) the places where we can find fossils, (the places where we) have physically found fossils and how many times people have gone to look for fossils (in these places).' The information was fed into a computer model, and Dean and his colleagues compared the physical fossil record with that proposed by the model and found a mismatch. The model suggested that, during the 18 million-year time period in question, the proportion of land the four dinosaur clades likely occupied remained constant overall, suggesting their potential habitat area remained stable, and the risk of extinction stayed low. One of the factors that could have clouded the true diversity patterns of dinosaurs was the lack of rock exposed at the Earth's surface during that window of time — and thus available for fossil hunters today to scrutinize. 'In this study, we show that this apparent decline is more likely a result of a reduced sampling window, caused by geological changes in these terminal Mesozoic fossil-bearing layers — driven by processes such as tectonics, mountain uplift, and sea-level retreat — rather than genuine fluctuations in biodiversity,' said study coauthor Alfio Alessandro Chiarenza, a Royal Society Newton International Fellow at University College London's department of Earth sciences, in a statement. 'Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic,' Chiarenza said. 'If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds.' The study helped to highlight what biases may affect scientists' understanding of the true pattern of dinosaur diversity leading up to the extinction event, said Darla Zelenitsky, a paleontologist at the University of Calgary in Alberta who wasn't involved in the research. 'Because of the nature of the rock record, (paleontologists have) found it was more difficult to detect dinosaurs and thus understand their diversity patterns in that window of time just before the mass extinction,' she said. 'It certainly makes sense as we know there are biases related to the rock record that can obscure true biological patterns. The more rock that is exposed at the surface (today), the better our chance of finding dinosaurs in that rock, which in turn leads to a better understanding of their diversity patterns.' Mike Benton, a professor of vertebrate paleontology at the UK's University of Bristol, called the paper 'thorough and detailed' but said it doesn't prove there was no reduction in dinosaur diversity ahead of the extinction event. Benton's work has suggested that dinosaurs were in decline before the asteroid wiped them out. He wasn't involved in the new study. 'The current paper suggests that the 'reduction' can be explained as a statistical artefact,' Benton said via email. 'What it shows is … simply that the reduction could be real or could be explained by reduced sampling, in my opinion.'
Yahoo
09-04-2025
- Science
- Yahoo
Dinosaurs weren't going extinct before the asteroid strike
When you buy through links on our articles, Future and its syndication partners may earn a commission. Dinosaurs weren't in decline when an asteroid smashed into Earth and wiped them out, scientists say. Instead, the idea that dinosaur diversity was declining before the asteroid struck 66 million years ago is likely based on faulty fossil data, according to a study that looked at nearly 18 million years of fossil evidence. Fossil discoveries have long indicated that dinosaurs were shrinking in numbers and diversity prior to the asteroid impact at the end of the Cretaceous period. Previously, some researchers believed this was a sign that dinosaurs were already on the road toward extinction even before the cataclysmic encounter with a space rock. However, this idea has long been controversial, with other researchers arguing that dinosaur diversity was doing just fine at the time of their demise. "It's been a subject of debate for more than 30 years — were dinosaurs doomed and already on their way out before the asteroid hit?" study lead author Chris Dean, a paleontologist at University College London, said in a statement. Now, new research published Tuesday (April 8) in the journal Current Biology suggests that the apparent rarity of dinosaurs before their extinction may simply be due to a poor fossil record. The scientists studied records of around 8,000 fossils from North America dating to the Campanian age (83.6 million to 72.1 million years ago) and Maastrichtian age (72.1 million to 66 million years ago), focusing on four families: the Ankylosauridae, Ceratopsidae, Hadrosauridae and Tyrannosauridae. At face value, their analysis showed that dinosaur diversity peaked around 76 million years ago, then shrank until the asteroid strike wiped out the nonavian dinosaurs. This trend was even more pronounced in the 6 million years before the mass extinction, with the number of fossils from all four families decreasing in the geological record. However, there is no indication of environmental conditions or other factors that would explain this decline, the researchers found. All of the dinosaur families were widespread and common, according to models developed by the researchers — and thus at low risk for extinction, barring a catastrophic event such as the asteroid impact. Rather, the Maastrichtian may have had poorer geological conditions for fossilization, the researchers suggested. Events such as the retreat of the Western Interior Seaway, which once ran from the Gulf of Mexico up through the Arctic, and the rise of the Rocky Mountains starting around 75 million years ago, may have impeded or disrupted fossilization, making it appear as if there were fewer dinosaurs and less diversity during that time. The team also found that geological outcrops from the Maastrichtian of North America were not exposed, or were covered by vegetation. In other words, rock from this time that might hold dinosaur fossils was not readily accessible to researchers who were searching for the remains. Because half of the known fossils from this period are from North America, the study's findings may have global implications as well. RELATED STORIES —Dinosaurs dominated our planet not because of their massive size or fearsome teeth — but thanks to the way they walked —'Exquisitely preserved' ginormous claws from Mongolia reveal strange evolution in dinosaurs —166 million-year-old fossil found on Isle of Skye belongs to pony-size dinosaur from Jurassic Among the 8,000 fossil records examined, the team found that Ceratopsians — a group that includes horned dinosaurs like Triceratops and its relatives — were the most common, probably because they inhabited plain regions that were most conducive to preservation during the Maastrichtian. Hadrosaurians — duck-billed dinosaurs — were the least common, possibly due to their preference for rivers. Reductions in river flow may have led to fewer depositions of sediment that could have preserved these dinosaurs, the researchers wrote in the study. "Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic [252 million to 66 million years ago]," study co-author Alfio Alessandro Chiarenza, a paleontologist at University College London, said in a statement. "If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds."
