Longer than a giraffe's: how could this beast fly without breaking its neck?

By 14/04/2021 Portal

If some creatures were designed to become a nightmare, they were the pterosaurs
, giant flying reptiles with an impressive wingspan of up to 12 meters. Cousins to dinosaurs and the largest animals that have ever flown, these now-extinct winged demons appeared about 225 million years ago. One of its most notable features was a disproportionate neck, longer than that of a giraffe. A team of British researchers has discovered how they managed to support it: its thin vertebrae had an intricate internal structure never seen before. They tell it in iScience.

The structure consists of a series of thin, rod-shaped trabeculae - small intersecting bone extensions - arranged like the spokes of a bicycle wheel. "Evolution transformed these creatures into amazing, incredibly efficient aviators," says Dave Martill of the University of Portsmouth, UK. "It is different from anything previously seen in a vertebra of any animal," he says.

Scientists previously thought that the pterosaur's neck had a simpler tube-within-a-tube structure. But this raised an important question: How could their thin-walled bones, needed to reduce the weight of flying reptiles, support their bodies while allowing them to capture and eat heavy prey?

"These animals have ridiculously long necks," says Cariad Williams, the study's first author. In some species, the fifth neck vertebra from the head is as long as the animal's body. When scanning the remains of a specimen found in Morocco with a CT scan, the researchers clearly observed the intricate internal structure of the vertebra.

«What was absolutely remarkable was that the internal structure was perfectly preserved. As soon as we saw the intricate pattern of radial trabeculae, we realized there was something a little special. As we looked closer, we could see that they were arranged in a helix that traveled up and down the spinal tube and crossed each other like spokes on a bicycle wheel," explains Martill.

A work of engineering
The team sought help from engineers to understand how the biomechanics of this unusual neck would have worked. Those analyzes suggest that just 50 of the spoke-like trabeculae increased the amount of weight the neck could support without bending on a 90%. Together with the basic tube-within-a-tube structure, they explain how relatively light animals could capture and carry heavy prey without breaking their necks.

"It seems that this structure of extremely thin cervical vertebrae resolved many concerns about the biomechanics of how these creatures were able to support massive heads, over 1.5 meters, on necks longer than those of a modern-day giraffe, all while retaining powered flight capability,” says Martill.

While pterosaurs are sometimes thought of as evolutionary dead ends, the researcher and his colleagues say the new findings reveal them to be "fantastically complex and sophisticated." Their bones and skeletons were marvels of biology: extremely light but strong and durable.

Researchers say there is still a lot to learn about pterosaurs, including seemingly basic questions about their flight abilities.