These Winged Dinosaurs Hurtled Through the Trees like Haywire Hang Gliders

During a blip in time in the late Jurassic, a dinosaur that weighed no more than a chinchilla flung itself from tree to tree, spread its wings and tried to soar. In theory, it sounds beautiful — an early attempt at flight before birds figured out the blueprint.

In practice, it was chaotic.

The dinosaur, Yi qi, only barely managed to glide, stretching out and shimmying its skin-flap, downy-feathered wings in a valiant attempt at flying. “It was rocketing from tree to tree, desperately trying not to slam into something,” said Alex Dececchi, a paleontologist at Mount Marty University in South Dakota. “It wouldn’t be something pleasant.”

Unsurprisingly, Yi qi is not an ancestor of modern birds. It went extinct after just a few million years, presumably doomed by its sheer lack of competency in the air. In a study published Thursday in the journal iScience, Dr. Dececchi and other researchers analyzed how Yi qi and the dinosaur Ambopteryx could have flown. Both animals were scansoriopterygids, a little-known group of small dinosaurs. The researchers did not expect the two to be great fliers, but their results painted a picture of bumbling creatures that weren’t truly at home on the ground, among the trees or in the sky.

Found by a farmer in northeastern China, Yi qi was first described in 2015 by paleontologists Xing Xu, of the Chinese Academy of Sciences, and Xiaoting Zheng, of Linyi University. When Dr. Dececchi first learned about the dinosaur’s bizarre anatomy, he was taken aback. “I said words that cannot be put into print,” he said.

In addition to the batlike wings, which had never before been observed in a dinosaur, Yi qi had an extraordinary long bone jutting out from its wrist. “Like Edward Scissorhands,” said Michael Pittman, a paleontologist at the University of Hong Kong and an author on the paper.

In 2018, Dr. Dececchi presented Yi qi in one of his classes, as a way of teaching the scientific method: “Here’s a weird creature. How do you think it would fly?” The more he thought about the question, the more he wanted to answer it.

When Dr. Dececchi presented a preliminary paper on Yi qi at a conference in 2018, he saw a similar paper by Arindam Roy, a graduate student in Dr. Pittman’s lab. The scientists decided to collaborate, with Dr. Pittman reconstructing the dinosaur’s wing and Dr. Dececchi modeling its flight. When Ambopteryx was described in 2018, the scientists incorporated the dinosaur into the study.

Dr. Pittman’s lab scanned the fossil using a technique called laser-stimulated fluorescence to detect soft tissues that might have gone unnoticed when the Yi qi was first described. The laser technique revealed new soft tissues around the neck and face and provided close-up images of the membrane, which allowed Dr. Pittman to revise the model for what Yi qi’s wing might have looked like.

With wing models in hand. Dr. Dececchi ran the dinosaurs through a panoply of mathematical models to test its flight ability. “I tried to give them the benefit of the doubt: the biggest wings, the most muscles, the fastest flapping,” he said.

The creatures failed even the most generous models. Their pectoral muscles were too weak to achieve flapping flight. They could not sprint fast enough to launch themselves from the ground. They were poor turners. They could not even take off after running on an incline while furiously flapping their wings.

The only scenario left was a bumbling glide wherein the dinosaurs stretched out their arms like flying squirrels and jumped from tree to tree, clattering among the branches.

Dr. Xu, who led the study first describing Yi qi, said he found the new paper’s analysis rigorous, although he was a bit surprised by how poorly the dinosaur seemed to fly. “I don’t consider this a final word on the flight capabilities of Yi,” he said, adding that the discovery of better-preserved specimens may produce different results.

“It’s a nice exploration of an odd group,” said Jingmai O’Connor, a curator of fossil reptiles at the Field Museum who also described Yi qi. “However, the authors seem to be reading too much into a handful of poorly preserved specimens.” She noted that only three adult scansoriopterygid fossils are known to science.

Yi qi and Ambopteryx’s strategy may have worked in the short-term. But as early birds took over the skies, eagle-size pterosaurs leered from above, and wolf-size dinosaurs salivated from below, the scansoriopterygids tumbled into extinction.

Although their failed flights offer little insight into how true birds evolved from dinosaurs, they shed light on the many ways that creatures tried to take to the skies. “The more fossils we find, the more we see how messy this evolutionary transition was,” said Steve Brusatte, a paleontologist at the University of Edinburgh who was not involved with the research.

In Dr. Dececchi’s eyes, the dinosaurs might have skirted doom if they had more time to evolve past the equivalent of their awkward teen years. “Then today, you might have had bats, birds and these weird and wonderful guys,” he said.

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