Flying lizards with giraffe-like necks and wing spans up to nearly 40 feet once ruled the skies while dinosaurs roamed below. These impressive albeit bizarre beasts, the azhdarchid pterosaurs, lived from the Late Triassic period until near the end of the Cretaceous period, and are the largest known vertebrates to ever take flight.
Scientists have long wondered how these ancient lizards could support their heads—their bones, like those of most birds, are quite lightweight and fragile. Especially if they were carrying prey in their mouths, the weight of the skull would be quite difficult to hold up with such a long, thin neck. But new research published this week in iScience shows that these animals had unique bone structure: Their vertebrae had fine struts that extended from a central neural tube out to the vertebra wall, similar to the spokes of a bicycle. The effect is a helix-like structure of support.
“It is unlike anything seen previously in a vertebra of any animal,” paleobiologist and co-author David Martill said in a statement. “This structure… resolved many concerns about the biomechanics of how these creatures were able to support massive heads—longer than 1.5 meters—on necks longer than the modern-day giraffe, all whilst retaining the ability of powered flight.”
Martill and his team made this discovery by examining azhdarchid pterosaur fossils from the Kem Kem site in Morocco—a fossil-rich area, and one of the only places you can find relatively intact Azhdarchid specimens. They placed pterosaur vertebrae through a CT scan, and they were amazed by the structures they found inside.
With the help of biomechanical engineers, they then assessed just how helpful the spoke-like structures were for easing the flying reptiles’ neck strain. Their analyses found that just 50 of these struts (with limited fossil records it’s hard to be sure exactly how many each creature had) increased their weight-bearing capacity by 90 percent, which explains how these ancient lizards could be such strong fliers and fierce predators without breaking their own necks.
Neck strength could have also been important to these pterosaurs for “neck bashing,” a type of rivalry-driven ritual between males that giraffes engage in today.
Knowing the structure of these vertebrae will help scientists gain more accurate understanding of azhdarchid pterosaurs—from how they moved, to the prey they might have been able to catch, and how big they really could have gotten.
Regardless, the never-before-seen neck vertebrae structure is quite a discovery, Martill said, and shows how “evolution shaped these creatures into awesome, breathtakingly efficient flyers.”
