Smaller pterosaurs may have flapped their wings, while larger ones may have flown.
Terryl Whitlatch
Despite living hundreds of millions of years apart, pterosaurs may be more similar to modern birds than previously thought: the bone structure of these giant reptiles suggests that the largest used wings to fly, while smaller ones flapped their wings to achieve flight.
The discovery comes from a remarkably well-preserved pterosaur fossil unearthed in Jordan: “The mechanics of flight leave traces in the skeleton,” says Jeffrey Wilson Mantilla of the University of Michigan.
Pterosaurs began flying about 80 million years before birds and bats. During their 150 million year reign, from the Triassic to the end of the Cretaceous period, they conquered every continent and evolved into a wide variety of sizes and shapes. Some were as small as a sparrow, while others had wingspans the size of a city bus. Analysis of pterosaur bones has revealed that different pterosaurs used different flight tactics to stay airborne.
Wilson-Mantilla and his team compared the fossils of two different pterosaur species and were delighted to discover that the 3D structure of the bones was still intact, which was a surprise because the hollow, brittle bones of pterosaurs would have easily broken down. Computed tomography scans revealed that the bones of the two reptile species were significantly different.
Large pterosaur, Arambrugiana Philadelphiahad spiral ridges running up and down the inside of their bones, similar to modern birds like eagles that fly with their wings fixed. Inabatanin Arabia The bird, a new species to science, had crossed struts that mimicked those of flapping birds.
The helical spiral helps resist twisting forces during ascent, while the crisscross footings withstand bending forces from the flaps, Wilson Mantilla said.
Because the team found the fossils in what was once a coastal area, Mantilla thinks the soaring pterosaurs may have gained altitude by riding updrafts (currents of warm air rising from the ocean surface). He speculates that these pterosaurs could have also flapped their wings specifically to take to the air, making their soaring trait even more unusual.
The reason why one of these pterosaurs appeared to be flapping and the other was soaring raises new questions about how the more than 100 other known pterosaur species flew. Mantilla next wants to examine fossils from around the world to see if this pattern holds true. Perhaps, like modern birds, only the largest individuals of their species were able to soar.
topic:
