The vertebral column in ornithischian dinosaurs was strengthened by means of structures called “ossified tendons.” These were actually tissues that connected the vertebrae together. They became filled with calcium, literally turning to bone (called ossifying). The result of this was a stiffening and strengthening of the connection between vertebrae, resulting in a strengthened backbone.

On ornithischian dinosaurs, ossified tendons appear as bony strands that look like spaghetti. Different names are given to them depending on where they are located on the dinosaur. For example, those between the tail vertebrae are called hypaxial tendons. In ornithischian dinosaurs, one purpose of the ossified tendons was to stiffen the base of the tail, making it more rigid with respect to the hips, while the tip of the tail was left mobile and flexible.