These tiny, little-winged dinosaurs were probably worse at flying than chickens

The discovery of two small dinosaurs with bat-like wings a few years ago was a palaeontologist’s dream. Just how flight evolved in birds is something we’re still trying to nail down, and looking at this early evolution of bat-like wings in dinosaurs could give us a clue.  



a close up of a bird: A drawing of the theropod dinosaur Yi qi, which sported bat-like wings.


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A drawing of the theropod dinosaur Yi qi, which sported bat-like wings.

But a team of researchers has now pointed out that just because you have wings, it doesn’t necessarily mean you’re actually any good at flying.

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Yi qi and Ambopteryx longibrachium are two species of theropod dinosaurs that lived around 160 million years ago, both of which had unusually elongated fingers, and a skin membrane stretching between them, similar to a bat’s wing.

This is an entirely different kind of wing to the one theropod dinosaurs evolved to fly with – the dinosaurs that eventually became birds. And, unlike them, after only a few million years, Yi and Ambopteryx became extinct, which is the first hint that these unusual wings could not match those birds-to-be. 

However, weird wings on extinct critters mean it’s likely multiple types of wings (and therefore flight) evolved over the years, and that Yi and Ambopteryx’s attempts were not the winning strategy.

But before you can write off Yi and Ambopteryx as complete evolutionary flight failures, you have to know how good (or bad, as the case may be) the two species were at flight.

In 2015, when Yi was found, that team of researchers suggested that the size of its wings and other flight characteristics could mean it was a gliding creature – however it’s unlike any other glider we know of, and its centre of mass might have made even gliding difficult. We just weren’t sure.

A new study, by researchers in the US and China, has now looked into the flight potential of Yi and Ambopteryx in a lot more detail, and come to the conclusion that they really weren’t good at getting their little feet off the trees they lived in.

“Using laser-stimulated fluorescence imaging, we re-evaluate their anatomy and perform aerodynamic calculations covering flight potential, other wing-based behaviors, and gliding capabilities,” the team writes.

“We find that Yi and Ambopteryx were likely arboreal, highly unlikely to have any form of powered flight, and had significant deficiencies in flapping-based locomotion and limited gliding abilities.”

The team’s analysis of the fossils (Yi pictured below) was able to pick up tiny details in soft-tissue that you can’t see with normal light.

Then the team modeled how the dinosaurs might have flown, adjusting for things such as weight, wingspan, and muscle placement (all stuff we can’t tell just from the fossils).

The results were … underwhelming.

“They really can’t do powered flight,” says first author, biologist Thomas Dececchi from Mount Marty University.

“You have to give them extremely generous assumptions in how they can flap their wings. You basically have to model them as the biggest bat, make

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Dinosaurs with bat wings ‘could barely fly, like chickens’ scientists reveal

How Ambopteryx might have looked in flight (McGill)
How Ambopteryx might have looked in flight (McGill)

Two tiny dinosaurs which had bat-like wings, could only manage a clumsy glide, and were wiped out by birds and other dinosaurs. 

Yi and Ambopteryx were small animals from Late Jurassic China, living about 160 million years ago. 

They could only glide, researchers believe, after reconstructing them by scanning fossils. 

This meant they were unable to compete with rivals in the forests where they lived, and died out in just a few million years. 

“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.”

The research was published in the journal Cell. 

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Thomas Dececchi, Assistant Professor of Biology at Mount Marty University said,  “Once birds got into the air, these two species were so poorly capable of being in the air that they just got squeezed out.

 “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.”

Weighing in at less than two pounds, they are unusual examples of theropod dinosaurs, the group that gave rise to birds.

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 other plants.

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Dececchi and his collaborators scanned fossils using laser-stimulated fluorescence (LSF), a technique that uses laser light to pick up soft-tissue details that can’t be seen with standard white light. 

Later, the team used mathematical models to predict how they might have flown, testing many different variables like weight, wingspan, and muscle placement.

Dececchi said, “They really can’t do powered flight. You have to give them extremely generous assumptions in how they can flap their wings. 

“You basically have to model them as the biggest bat, make them the lightest weight, make them flap as fast as a really fast bird, and give them muscles higher than they were likely to have had to cross that threshold.

“They could glide, but even their gliding wasn’t great.”

While 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 did help Yi and Ambopteryx stay out of danger while they were still alive.

Dececchi said, “If an animal needs to travel long distances for whatever reason, gliding costs a bit more energy at the start, but it’s faster. It can also be used as an escape hatch. It’s not a great thing to do, but

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