Despite having bat-like wings, two small dinosaurs, Yi and Ambopteryx, struggled to fly and managed to clumsily slide between the trees in which they lived, researchers report today (Oct.22, 2020) in the journal. iScience. Unable to compete with other tree-dwelling dinosaurs and early birds, they are extinct after a few million years. The results support that dinosaurs evolved their flight in many different ways before modern birds evolved.
“Once the birds got into the air, these two species were so weak in the ability to exist in the air that they were just expelled,” says first author Thomas Dikishi, assistant professor of biology at Mount Marty University. “Maybe you can survive a few million years substandard, but you have predators from above, competition from the bottom, and even some small mammals add to that, and you squeeze them until they are gone.”
Yi and Ambopteryx were young animals of the late Jurassic China lived about 160 million years ago. Weighing less than two pounds, they are unusual examples of theropod dinosaurs, the group that gave birth to birds. Most theropods were earth-loving carnivores, but Ye and Ambopterx were at home in the trees and subsisted on a diet of insects, seeds, and other plants.
Curious about how these animals fly, Dececchi and his collaborators scanned the fossils with laser stimulated fluorescence (LSF), a technique that uses laser light to capture soft tissue details that cannot be seen with standard white light. Later, the team used mathematical models to predict which way they might have flown, and tested many different variables such as weight, wingtip and muscle position.
“They really can’t take a flight that’s powered by energy. You have to give them very generous assumptions about how they flap their wings. You have to design them as the biggest bats, make them lighter, get them to flap as fast as possible for really fast birds, and give them higher muscle than they would have been.” They have had to cross this limit, ”says Dheikishi. “They can slide, but even their glide isn’t great.”
While paragliding is not an effective form of flying, as it can only be done if the animal has actually climbed to a high point, it did help Yi and Ambopterx to stay out of danger while they were still alive.
“If an animal needs to travel long distances for any reason, paragliding costs a little more energy at first, but it’s faster. It can also be used as an escape hole. It’s not a great thing to do, but sometimes it’s a choice between losing a little bit of energy.” And eat, “says Daikishi. “Once they were under pressure, they lost their space. They couldn’t win on the ground. They couldn’t win in the air. They were done.”
Researchers are now looking at the Yi-powered muscles and Ambopteryx to create an accurate picture of these strange little creatures. “I used to work with older birds, and kind of have an idea of what they really look like,” says Dikishi. “Working where we’re just trying to discover the potential of an alien creature is kind of fun.”
Reference: “Presentation of Aerodynamics of Winged Theropods with Membranes that were a Weak Sliding Dead End” by T. Alexander Dikishi, Arendam Roy, Michael Bateman, Thomas J. Kay, Cheng Shuo, Michael B. Zheng, October 22, 2020 iScience.
DOI: 10.1016 / j.isci.2020.101574
The authors were supported by Mount Marty University and The University of Hong Kong.