Two magpie-sized dinosaurs that lived 160 million years ago evolved the ability to glide but were poor flyers, a new study shows.
Despite having bat-like wings, the two foot-long, feathered dinosaurs, called Yi and Ambopteryx, only managed to glide clumsily between the trees, say US researchers.
Their poor aerial ability meant they eventually died out due to competition from better flyers and hunters.
Yi, discovered in 2015, and Ambopteryx, only discovered last year, were part of an extinct family of gliding dinosaurs called the scansoriopterygids.
Experts used computer modelling that simulated their wing and muscle movements based on fossils to work out how badly they really flew.
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Two recently-discovered dinosaurs of the scansoriopterygid family, Yi and Ambopteryx, glided clumsily between the trees before they went extinct
Illustration shows a reconstruction of Ambopteryx in a glide. It’s one of two tiny dinosaurs that lived about 160 million years ago that struggled to fly despite having bat-like wings
WHAT IS GLIDING?
Gliding flight is a comparatively inexpensive flight mode.
Instead of the bird actively adding energy by flapping its wings, energy for the forward motion is instead harvested from the potential energy.
This means, however, that the bird will lose altitude as it flies forward and, if not resuming flapping or gaining altitude by soaring at some point, will end up on the ground.
Definition: Lund University
Yi and Ambopteryx were capable of ‘poor gliding’ and were unable to launch from the ground or used ‘wing assisted incline running’ – where birds run up steep or vertical inclines by flapping their wings.
‘Once birds got into the air, these two species were so poorly capable of being in the air that they just got squeezed out,’ said study author Thomas Dececchi at Mount Marty University in South Dakota.
‘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.
‘To work where we’re just trying to figure out the possibilities for a weird creature is kind of fun.’
Yi and Ambopteryx were small animals from Late Jurassic China, living about 160 million years ago.
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-based carnivores, but Yi and Ambopteryx were at home in the trees and lived on a diet of insects, seeds and plants.
This graphic shows a map of the skeleton and soft tissues of Yi. LSF stands for laser-stimulated fluorescence
To learn more about how these animals fly, 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 and published their findings in iScience.
The team have determined that they were able to take advantage of drafts by gliding, but even then ‘their gliding wasn’t great’.
‘They really can’t do powered flight – you have to give them extremely generous assumptions in how they can flap their wings,’ said Dececchi.
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.
The new dinosaur, named Yi qi (shown above in the artists reconstruction), had unusual bristle-like feathers and bat-like wings that were covered in a membrane. The dinosaur may have been able to glide and flap
‘If an animal needs to travel long distances for whatever reason, gliding costs a bit more energy at the start, but it’s faster,’ said Dececchi.
‘It can also 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 at the muscles that powered Yi and Ambopteryx to construct an accurate image of these creatures.
Yi and Ambopteryx were capable of poor gliding under narrow conditions and were unable to launch from the ground or wing assisted incline running – where birds can run up steep or vertical inclines by flapping their wings
The sole species in the Ambopteryx genus – Ambopteryx longibrachium – was only reported last year by Chinese scientists.
Its remains, which were found in Liaoning Province, China, led experts to conclude that the magpie-sized therapod had a long wrist bone that likely supported its membranous wings.
The only species in the Yi genus – Yi qi, named after the Mandarin for ‘strange wing’ – was also found in China and described by scientists in 2015.
Membrane wings and long forelimbs of scansoriopterygids represent a short-lived experimentation with flight that would have occurred before the later predominance of feathered wings.
Scansoriopterygids form a group of tiny dinosaurs that are generally reconstructed as feathered tree climbers, with very long hands and fingers.
Several features distinguish Ambopteryx from its cousin Yi, including a wider forelimb bone, a short tail ending in fused vertebrae and an elongated forelimb that is longer than the hindlimb.
HOW THE DINOSAURS WENT EXTINCT AROUND 66 MILLION YEARS AGO
Dinosaurs ruled and dominated Earth around 66 million years ago, before they suddenly went extinct.
The Cretaceous-Tertiary extinction event is the name given to this mass extinction.
It was believed for many years that the changing climate destroyed the food chain of the huge reptiles.
In the 1980s, paleontologists discovered a layer of iridium.
This is an element that is rare on Earth but is found in vast quantities in space.
When this was dated, it coincided precisely with when the dinosaurs disappeared from the fossil record.
A decade later, scientists uncovered the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, which dates to the period in question.
Scientific consensus now says that these two factors are linked and they were both probably caused by an enormous asteroid crashing to Earth.
With the projected size and impact velocity, the collision would have caused an enormous shock-wave and likely triggered seismic activity.
The fallout would have created plumes of ash that likely covered all of the planet and made it impossible for dinosaurs to survive.
Other animals and plant species had a shorter time-span between generations which allowed them to survive.
There are several other theories as to what caused the demise of the famous animals.
One early theory was that small mammals ate dinosaur eggs and another proposes that toxic angiosperms (flowering plants) killed them off.