Dinosaurs

How the Largest Animals That Could Ever Fly Supported Giraffe-Like Necks

These pterosaurs had wingspans as long as 33 feet, and scans of fossilized remains reveal a surprise in their anatomy.

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How the Largest Animals That Could Ever Fly Supported Giraffe-Like Necks

These pterosaurs had wingspans as long as 33 feet, and scans of fossilized remains reveal a surprise in their anatomy.

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An end-to-end CT scan of a fossilized pterosaur vertebra reveals the spoke-like structures inside. Video by Williams et al.CreditCredit…Williams et al., iScience

By Becky FerreiraPublished April 14, 2021Updated April 15, 2021SIGN UP FOR SCIENCE TIMES: Get stories that capture the wonders of nature, the cosmos and the human body.Sign Up

If you were to gaze skyward in the late Cretaceous, you might catch a glimpse of surreal flying giants with wingspans that rival small planes. This supersized group of pterosaurs, known as azhdarchids, included species that measured 33 feet between wingtips, which made them the largest animals that ever took to the air.

The extreme dimensions of azhdarchids raise tantalizing questions, such as how they carried large prey without breaking their long necks, or how animals the size of giraffes effortlessly soared above their dinosaur relatives on the ground.

Cariad Williams, a Ph.D. student at the University of Illinois at Urbana-Champaign, was hoping to shed some light on these questions with the help of an azhdarchid specimen from the Kem Kem fossil beds of Morocco. She used a CT scan to study fossils from the animal’s neck.

“We just couldn’t believe the structure that we found inside,” Ms. Williams said.

The results, published on Wednesday in the journal iScience, stunned Ms. Williams and her colleagues. The animal’s neck was revealed to be scaffolded by a unique and complex network of helical struts connecting a central neural tube to the vertebra wall like the spokes of a bicycle. It was a structure that has no parallel elsewhere in the animal kingdom.

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This unprecedented peek into an azhdarchid neck helps to fill some of the persistent gaps in our knowledge of their anatomy and behavior. Pterosaurs, like birds, evolved extremely fragile and lightweight skeletons to optimize their flight abilities; these qualities also cause them to be underrepresented in the fossil record because their bones easily break apart.

An artist’s rendering of a pterosaur, whose complex neck structure has no parallel elsewhere in the animal kingdom.
An artist’s rendering of a pterosaur, whose complex neck structure has no parallel elsewhere in the animal kingdom.Credit…Williams et al., iScience

The Kem Kem site is among the few places in the world where relatively intact azhdarchid fossils can be found. The Moroccan fossil beds preserve a lush river system that existed about 100 million years ago, attracting Cretaceous sharks, large predatory dinosaurs like Spinosaurus and Carcharodontosaurus, as well as azhdarchids.

Ms. Williams and her colleagues tentatively identified their specimen as an Alanqapterosaur. While it’s difficult to estimate its exact dimensions, the azhdarchid probably had a five-foot-long neck and a wingspan that measured between 20 to 26 feet.

A biomechanical analysis of the intricate structure of the neck revealed that the spokelike filaments bolstered the vertebrae against the pressures of catching and carrying heavy prey. According to the team’s calculations, the addition of only 50 struts increased by 90 percent the weight that they could bear without buckling, enabling this particular specimen to carry loads of up to 24 pounds, which Ms. Williams called “really impressive.”

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“They were using less energy to optimize their strength in their neck to be able to lift the prey,” she said.

The unusual adaptation may have functions beyond hunting and feeding, such as “neck ‘bashing,’ an intermale rivalry behavior seen in giraffes” or as a way to deal with the “shearing forces associated with large skulls being buffeted by strong winds during flight or while on the ground,” according to the study. Ms. Williams and her colleagues plan to follow up on their findings by scanning other azhdarchid vertebrae to assess whether the spoke structure is widespread.

David Hone, a paleontologist at Queen Mary, University of London, who was not involved in the study, said the new research provides a “nice confirmation” of the mechanical soundness of azhdarchid vertebrae.

“It’s a very neat finding that there is this weird arrangement of struts and that this is about the minimum possible to strengthen the bone,” he said. “But it’s also not much of a surprise as we know azhdarchids had incredibly reduced bones and were extraordinarily light for their size.”

“What we really need for azhdarchids is a well-preserved 3-D skeleton,” Dr. Hone concluded. “We are working from either flattened fossils or very incomplete specimens, which makes it hard to work out even a lot of basics.”

These Winged Dinosaurs Hurtled Through the Trees Like Haywire Hang Gliders

To call it flying would be generous.

The spastic, mostly flight-challenged Ambopteryx, a Jurassic-era dinosaur with mostly-useless bat-like wings.
The spastic, mostly flight-challenged Ambopteryx, a Jurassic-era dinosaur with mostly-useless bat-like wings.Credit…Gabriel Ugueto

By Sabrina ImblerPublished Oct. 22, 2020Updated Oct. 23, 2020SIGN UP FOR SCIENCE TIMES: Get stories that capture the wonders of nature, the cosmos and the human body.Sign Up

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.

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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.

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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.