If you had been to gaze skyward within the late Cretaceous, you would possibly catch a glimpse of surreal flying giants with wingspans that rival small planes. This supersized group of pterosaurs, referred to as azhdarchids, included species that measured 33 ft between wingtips, which made them the biggest animals that ever took to the air.
The excessive dimensions of azhdarchids increase tantalizing questions, resembling how they carried massive prey with out breaking their lengthy necks, or how animals the scale of giraffes effortlessly soared above their dinosaur family members on the bottom.
Cariad Williams, a Ph.D. scholar on the University of Illinois at Urbana-Champaign, hoped to shed some gentle on these questions with the assistance of an azhdarchid specimen from the Kem Kem fossil beds of Morocco. She used a CT scan to check fossils from the animal’s neck.
“We just couldn’t believe the structure that we found inside,” Ms. Williams mentioned.
The outcomes, published on Wednesday within the journal iScience, surprised Ms. Williams and her colleagues. The animal’s neck was revealed to be scaffolded by a singular and complicated community of helical struts connecting a central neural tube to the vertebra wall just like the spokes of a bicycle. It was a construction that has no parallel elsewhere within the animal kingdom.
This unprecedented peek into an azhdarchid neck helps to fill a few of the persistent gaps in our data of their anatomy and conduct. Pterosaurs, like birds, developed extraordinarily fragile and light-weight skeletons to optimize their flight skills; these qualities additionally trigger them to be underrepresented within the fossil document as a result of their bones simply break aside.
The Kem Kem web site is among the many solely place on the earth the place comparatively intact azhdarchid fossils could be discovered. The Moroccan fossil beds protect a lush river system that existed about 100 million years in the past, attracting Cretaceous sharks, massive predatory dinosaurs like Spinosaurus and Carcharodontosaurus, in addition to azhdarchids.
Ms. Williams and her colleagues tentatively recognized their specimen as an Alanqa pterosaur. While it’s troublesome to estimate its precise dimensions, the azhdarchid in all probability had a five-foot-long neck and a wingspan that measured between 20 to 26 ft.
A biomechanical evaluation of the intricate construction of the neck revealed that the spokelike filaments bolstered the vertebrae towards the pressures of catching and carrying heavy prey. According to the staff’s calculations, the addition of solely 50 struts elevated by 90 p.c the load that they may bear with out buckling, enabling this explicit specimen to hold a great deal of as much as 24 kilos, which Ms. Williams known as “really impressive.”
“They were using less energy to optimize their strength in their neck to be able to lift the prey,” she mentioned.
The uncommon adaptation could have features past looking and feeding, resembling “neck ‘bashing,’ an intermale rivalry behavior seen in giraffes” or as a method to take care of the “shearing forces associated with large skulls being buffeted by strong winds during flight or while on the ground,” in line with the examine. Ms. Williams and her colleagues plan to comply with up on their findings by scanning different azhdarchid vertebrae to evaluate whether or not the spoke construction is widespread.
David Hone, a paleontologist at Queen Mary, University of London, who was not concerned within the examine, mentioned the brand new analysis gives 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 mentioned. “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.”
