An elongated composite sacrum containing a number of fused vertebrae, present in birds and some extinct reptiles.
- ‘In most birds, diverticula of the abdominal air sacs pneumatize the posterior thoracic vertebrae and synsacrum later in ontogeny.’
- ‘Between the notarium and synsacrum were several dorsal vertebrae that may have provided some level of dorsoventral mobility.’
- ‘We glued transmitters on the bird above the synsacrum, with the antenna oriented down the tail; we placed the harness around each leg, in a figure-8 shape.’
- ‘The posterior thoracic vertebrae, synsacrum, and hindlimb are pneumatized by diverticula of the abdominal air sacs.’