Paleontologists have unearthed the fossils of two different large azhdarchoid pterosaurs. Inabatanin Arabia And previously known species Arambrugiana Philadelphia — Discovered in Upper Cretaceous deposits in Jordan, the fossils have led researchers to hypothesize that not only could the largest pterosaurs fly, but that they may have had a different style of flight.
Inabatanin Arabia (Top) Flying while flapping its wings Arambrugiana Philadelphia (Below) Soaring like a vulture. Image courtesy of Terrill Whitlatch.
Pterosaurs are an extinct group of flying reptiles that existed from the Late Triassic until the mass extinction at the end of the Cretaceous period.
They evolved powered flight about 50 million years before flight feathers appeared in the fossil record, and some achieved wingspans twice that of the largest flying birds (12 metres versus 6 metres).
“Our team was very surprised to find a three-dimensionally preserved pterosaur bone, which is a very rare occurrence,” said University of Michigan paleontologist Kerstin Rosenbach.
“Because pterosaur bones are hollow, they are extremely fragile and, if preserved, are likely to be found flat like a pancake.”
Dr. Rosenbach and his colleagues discovered two azhdarchoid pterosaur specimens in Jordan, one of which corresponds to a giant species. Arambrugiana Philadelphia (wingspan about 10 meters) and the second is a new, smaller species. Inabatanin Arabia (Wingspan approximately 5 meters).
They used high-resolution computed tomography (CT) scans to analyze the internal structure of the wing bones.
“3D preservation is very rare, so we don’t have a lot of information about what the inside of a pterosaur bone looks like, so we wanted to do a CT scan,” Dr Rosenbach said.
“It’s entirely possible that nothing was preserved inside, or that the CT scanner was not sensitive enough to distinguish the fossil bone tissue from the surrounding matrix.”
“But fortunately, what we found was amazing, with exciting internal structures that were not only preserved but could be seen with a CT scanner.”
New specimens Arambrugiana Philadelphia Its wingspan was determined to be 10 metres, and the first details about the reptile’s skeletal structure were revealed.
CT scans revealed that the humerus is hollow inside, with a series of spiral ridges running up and down the bone, similar to the internal structure of a vulture’s wing bones.
The spiral ridges are thought to resist the torsional loads associated with soaring (sustained powered flight that requires flapping wings to launch and maintain).
The Inabutinin Arabian specimen is one of the most complete pterosaurs ever discovered in Afro-Arabia.
CT scans revealed that the structure of its flight bones is completely different from that of Arambourgiania philadelphiae.
The interior of the flight bone was crossed with an arrangement of struts that matched those seen in the wing bones of modern flapping birds.
This indicates that it was adapted to withstand the bending loads associated with flapping flight, and so it is likely that Inabatanin flew in this way, although it does not exclude the possibility that other flight styles may have been used from time to time.
” Inabatanin Arabia “It’s not uncommon, but it’s fun to see,” Dr. Rosenbach said.
” Arambrugiana Philadelphia It was totally unexpected and at first I had no idea what I was looking at.”
“Being able to see the entire 3D model, Arambrugiana PhiladelphiaI was really excited to see the spiral ridges on the humerus.”
The discovery of diverse flight styles among different sized pterosaurs is extremely exciting as it gives clues about how these animals lived.
It also raises intriguing questions, such as to what extent flight style correlates with body size and which flight style is more common among pterosaurs.
“We have very limited information about the internal structure of pterosaur bones over time, so it’s hard to say with any certainty which style of flight emerged first,” Dr Rosenbach said.
“If you look at other groups of flying vertebrates, birds and bats, you’ll find that wing flapping is by far the most common flight behavior.”
“Even soaring and gliding birds need some flapping to take to the air and continue flying.”
“This leads us to suggest that if flapping flight was the default state and was advantageous for a population of pterosaurs in a particular environment, in this case the open ocean, then soaring behaviour probably evolved later.”
a paper The paper on the survey results is Journal of Vertebrate Paleontology.
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Kirsten L. Rosenbach othersNew pterosaur fossils from the Afro-Arabian Late Cretaceous provide insight into the flying capabilities of large pterosaurs. Journal of Vertebrate PaleontologyPublished online September 5, 2024; doi: 10.1080/02724634.2024.2385068
Source: www.sci.news
