Sacral Vertebrae

The sacral vertebrae support the bones of the pelvis.  They are often preserved in groups due to the fact that they were  fused in life.  The number of vertebrae in the sacrum varies between species, but will be generally between 3 and 10.

Whilst there is a great deal of variation in the form of the pelvis across pterosaur species, the form of the sacral vertebrae is essentially the same.  The cenra are fused, forming an ankylose bone mass.  The neural arch tends to have a triangular shaped canal and both the dorsal and transverse processes are fused to the pelvic bones.  Pneumatic foramen are present in most of the centra.

The sacral vertebrae of Rhamphorhynchus are sturdy structures forming part of the pelvic girdle.  They are fused to the pelvis at the ilium bone.  There is a variation across different Rhamphorhynchus species, but all are similar to this form which is Rhamphorhynchus muensteri.

The far side of the pelvis is shown in position.

Pterodactylus is a short tailed pterosaur and the sacral vertebrae are more in number.  With a shorter and very sturdy pelvic girdle, this form is typical of the more advanced pterosaurs.

As pterosaur species become larger, the number of sacral vertebrae and the length of the pelvic bones increases.  Pteranodon has 10 sacral vertebrae.