Early dinosaurs were faster and more dynamic than their competitors, according to a study led by University of Bristol researcher Amy Shipley.
By adopting more diverse limb morphologies and styles, dinosaurs may have been able to occupy more terrestrial habitats and greatly diversify extinction events. Image credit: Sergey Krasovskiy.
In their study, Shipley and colleagues compared the limb proportions of a wide range of Triassic reptiles. The Triassic period is the period from 252 million years ago, when dinosaurs first appeared and became famous, to 201 million years ago.
They determined which of these ancient beasts were quadrupedal (quadrupedal) or bipedal (bipedal), and also examined the cursority index, a measure of running ability.
Researchers found that not only were dinosaurs and their relatives bipedal from the beginning, meaning they had limbs adapted for running, but they also We found that it showed a much wider range of running styles. pseudostia.
Pseudonesians also included the ancestors of modern crocodiles. Although there were some small bipedal animals that ate insects, most were medium to large carnivores or herbivores, and they were diverse throughout the Triassic.
The authors believe that dinosaurs and their relatives bird metatarsal maintained a higher range of motor modes throughout this period.
“When the crisis hit 233 million years ago, the dinosaurs won,” Shipley said.
“At that time, the climate changed from wet to dry and there was severe pressure on food.”
“For some reason, dinosaurs, which had been living in small numbers for 20 million years, appeared, but no pseudo-dinosaurs appeared.”
“Like many reptiles and birds today, early dinosaurs may have been good at conserving water.”
“However, our evidence shows that their high adaptability during walking and running played an important role.”
“After the mass extinction at the end of the Triassic period, dinosaurs expanded again,” added Professor Mike Benton from the University of Bristol.
“With the exception of the crocodile ancestors, most of the pseudodinosaurs went extinct in mass extinctions, and we found that these surviving dinosaurs once again expanded their range and took over many of the niches that had been vacated.”
“When we looked at the rate of evolution, we found that dinosaurs were not actually evolving particularly rapidly,” said co-author Dr Armin Elsler, a researcher at the University of Bristol.
“This was a surprise because we expected to see rapid evolution in ornithopods and slower evolution in pseudopods.”
“What this means is that while dinosaur locomotion style was advantageous for dinosaurs, it was not the driving force behind intense evolutionary selection.”
“In other words, when the crisis happened, they were in a better position to take advantage of the opportunities after the crisis.”
“We always think of dinosaurs as large, mobile animals,” says co-author Dr Tom Stubbs, also from the University of Bristol.
“This reminds us that dinosaurs actually started out as nifty little insect-eaters.”
“The first dinosaurs were only a meter long and walked bipedally with their legs raised high. Their leg posture meant they could move quickly and capture prey while fleeing from larger predators. I meant it.”
“And of course, dinosaurs' postural diversity and focus on fast running mean that dinosaurs could diversify given the opportunity,” said co-author Suresh Singh, also from the University of Bristol. the doctor said.
“After the mass extinction at the end of the Triassic period, truly gigantic dinosaurs emerged, over 10 meters long, some with armor, many quadrupedal, but many still bipedal, like their ancestors. Walking.”
“Their diversity of posture and gait means they are highly adaptable, and this ensured their great success for a long time on Earth.”
of study It was published in the magazine Royal Society Open Science.
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Amy E. Shipley other. 2024. Archosauromorph migration and early Mesozoic success. R. Soc. Open Science 11(2):231495; doi: 10.1098/rsos.231495
