Bat-winged dinosaurs that could glide

October 22, 2020

Despite having bat-like wings, two small dinosaurs, Yi and Ambopteryx, struggled to fly, only managing to glide clumsily between the trees where they lived, according to a new study led by an international team of researchers, including McGill University Professor Hans Larsson. Unable to compete with other tree-dwelling dinosaurs and early birds, they went extinct after just a few million years. The findings, published in iScience, support that dinosaurs evolved flight in several different ways before modern birds evolved.

"We know some dinosaurs could fly before they evolved into birds," says Professor Larsson, Director of McGill's Redpath Museum. "What this shows us is that at least one lineage of dinosaurs experimented with a completely different mode of aerial locomotion. Gliding evolved countless times in arboreal amphibians, mammals, lizards, and even snakes - and now we have an example of dinosaurs."

Yi and Ambopteryx were small animals from the Late Jurassic of China, living about 160 million years ago. Weighing in at about half a kilogram, they are unusual theropod dinosaurs. Theropods are carnivorous dinosaurs that include all birds alive today. Most theropods were ground-loving carnivores, but Yi and Ambopteryx were at home in the trees and lived on a diet of insects, seeds, and plants.

"Once birds got into the air, these two species were so poorly capable of being in the air that they just got squeezed out," says lead author Thomas Dececchi, an assistant professor of biology at Mount Marty University. "Maybe you can survive a few million years underperforming, but you have predators from the top, competition from the bottom, and even some small mammals adding into that, squeezing them out until they disappeared."

Little creatures could glide, not fly

Curious about how these animals could have flown, the researchers, scanned fossils using Laser-Stimulated Fluorescence (LSF), a technique that uses laser light to pick up soft tissue details of their wing membranes that can't be seen with standard white light. Later, the team used mathematical models to predict how they might have flown, testing different variables like weight, wingspan, wing shape, and muscle placement.

"The results are clear these animals were not able to fly like birds," says Larsson. "They didn't have adaptations to even get close to the physical thresholds for powered flight, but their weird membranous wings do give them enough of an aerofoil to have glided. They are not comparable to living gliding squirrels or lizards but seem to have come up with a really novel way of getting a large enough wing membrane."

Although gliding is not an efficient form of flight since it can only be done if the animal has already climbed to a high point, it probably did help Yi and Ambopteryx stay out of danger while they were still alive.

"Living gliders don't travel long distances through the air," says Dececchi. "It's not efficient, but it can be used as an escape hatch. It's not a great thing to do, but sometimes it's a choice between losing a bit of energy and being eaten. Once they were put under pressure, they just lost their space. They couldn't win on the ground. They couldn't win in the air. They were done."

The researchers are now looking more closely at the musculoskeletal anatomy of these bat-winged and other feathered dinosaurs that evolved around the origin of birds. "The diversity of dinosaurs just before the origin of birds amazes me," Larsson says. "We used to think of birds evolving as a linear trend from their ground-dwelling dinosaur ancestry. We can know revise this textbook scenario to one that had an explosive diversity of experimentation, with dinosaurs evolving powered flight several times independently from birds, many having fully feathered wings but with bodies too heavy or wings too small to have gotten off the ground, and now, a weird bat-winged group of dinosaurs that were not only the first arboreal dinosaurs, but ones that glided! I feel like we are still just scratching the surface."
-end-
About the study

"Aerodynamics show membranous-winged theropods were a poor gliding dead-end" by T. Alexander Dececchi, Arindam Roy, Michael Pittman, Thomas G. Kaye, Xing Xu, Michael B. Habib, Hans C.E. Larsson, Xiaoli Wang, and Xiaoting Zheng is published in iScience.

DOI: http://dx.doi.org/10.1016/j.isci.2020.101574

Website link: https://www.cell.com/iscience/fulltext/S2589-0042(20)30766-5

About McGill University

Founded in Montreal, Quebec, in 1821, McGill University is Canada's top ranked medical doctoral university. McGill is consistently ranked as one of the top universities, both nationally and internationally. It?is a world-renowned?institution of higher learning with research activities spanning two campuses, 11 faculties, 13 professional schools, 300 programs of study and over 40,000 students, including more than 10,200 graduate students. McGill attracts students from over 150 countries around the world, its 12,800 international students making up 31% of the student body. Over half of McGill students claim a first language other than English, including approximately 19% of our students who say French is their mother tongue.

http://www.mcgill.ca/newsroom/

McGill University

Related Dinosaurs Articles from Brightsurf:

Ireland's only dinosaurs discovered in antrim
The only dinosaur bones ever found on the island of Ireland have been formally confirmed for the first time by a team of experts from the University of Portsmouth and Queen's University Belfast, led by Dr Mike Simms, a curator and palaeontologist at National Museums NI.

Baby dinosaurs were 'little adults'
Paleontologists at the University of Bonn (Germany) have described for the first time an almost complete skeleton of a juvenile Plateosaurus and discovered that it looked very similar to its parents even at a young age.

Bat-winged dinosaurs that could glide
Despite having bat-like wings, two small dinosaurs, Yi and Ambopteryx, struggled to fly, only managing to glide clumsily between the trees where they lived, according to a new study led by an international team of researchers, including McGill University Professor Hans Larsson.

Some dinosaurs could fly before they were birds
New research using the most comprehensive study of feathered dinosaurs and early birds has revised the evolutionary relationships of dinosaurs at the origin of birds.

Tracking Australia's gigantic carnivorous dinosaurs
North America had the T. rex, South America had the Giganotosaurus and Africa the Spinosaurus - now evidence shows Australia had gigantic predatory dinosaurs.

Ancient crocodiles walked on two legs like dinosaurs
An international research team has been stunned to discover that some species of ancient crocodiles walked on their two hind legs like dinosaurs and measured over three metres in length.

Finding a genus home for Alaska's dinosaurs
A re-analysis of dinosaur skulls from northern Alaska suggests they belong to a genus Edmontosaurus, and not to the genus recently proposed by scientists in 2015.

Can we really tell male and female dinosaurs apart?
Scientists worldwide have long debated our ability to identify male and female dinosaurs.

In death of dinosaurs, it was all about the asteroid -- not volcanoes
Volcanic activity did not play a direct role in the mass extinction event that killed the dinosaurs, according to an international, Yale-led team of researchers.

Discriminating diets of meat-eating dinosaurs
A big problem with dinosaurs is that there seem to be too many meat-eaters.

Read More: Dinosaurs News and Dinosaurs Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.