Anatomy of the cervical vertebrae in tenysaurians

Bones with large hollow spaces are one of the characteristic features of dinosaurs (including birds) and pterosaurs. New research shows that the vertebrae of relatives of ancestors of these groups were also hollow inside. In tanysaurians, long-necked reptiles that lived in the Triassic, around 240 million years ago, the extremely elongated vertebrae had a cylindrical structure. Dense bone surrounded a single large cavity that took up most of the volume of a vertebra. Such vertebral anatomy is not known in any other animals. Unlike dinosaurs, however, bones of tanysaurians were not filled with air but with soft tissue. The cylindrical structure of the vertebrae increased their durability.

 

Illustration: Beat Scheffold and Jakub Zalewski