Helically arranged cross struts in azhdarchid pterosaur cervical vertebrae and their biomechanical implications

Area of Science:

• Paleontology
• Biomechanics
• Vertebrate Zoology

Background:

• Azhdarchid pterosaurs, the largest flying vertebrates, are poorly understood.
• Key aspects of their palaeobiology, including neck mechanics, remain largely unknown.

Purpose of the Study:

• To investigate the internal micro-architecture of hyper-elongate cervical vertebrae in the Cretaceous azhdarchid pterosaur, *Alanqa* sp.
• To analyze the biomechanical implications of this structure for axial loading and skeletal mass.

Main Methods:

• X-ray computed tomography was used to examine the three-dimensionally preserved vertebrae.
• Finite element modeling, linear elastic static analysis, and linearized buckling analysis were performed.

Main Results:

• A complex "tube-within-a-tube" internal structure was revealed, supported by helically distributed trabeculae.
• As few as 50 trabeculae increased the buckling load by up to 90%, significantly enhancing stability.
• The structure allows for uptake of heavy prey without damaging the neck and reduces skeletal mass.

Conclusions:

• The specialized cervical vertebrae of *Alanqa* sp. provided exceptional stiffness and resistance to elastic instability.
• This adaptation facilitated predation on large prey and contributed to efficient flight through skeletal mass reduction.