Vertebrae

The vertebral column of pterosaurs is quite distinctive.  It resembles that of birds in many ways, with a very rigid shoulder girdle and a very rigid pelvic region.  There are few dorsal vertebrae with limited movement.  Most isolated fossil vertebra finds tend to be cervicals.  To illustrate the form of the pterosaur vertebral column, Pteranodon is shown here.

The overall form is for a flexible neck, a rigid body and a tail with limited movement.  Pteranodon is a pterodactyloid form, which has a short tail.

Ax - Atlas and axis, often fused into one bone, joins the spinal column to the skull.

A - Cervical Vertebrae.  These are large in comparison with the other vertebrae.   There are usually 8 cervicals (including the atlas/axis) in the early pterosaurs, reducing to 6 in some of the later and the larger pterosaurs.  The cervicals have a thin outer layer of hard bone and a centre of cancellous (spongy) bone and pneumatic cavities (air pockets).  There are generally no cervical ribs.  Pneumatic foramen are prominent on the sides of the vertebrae.

B - Thoracic Vertebrae.  These can be up to 12 in some species, but there are usually less than this.  The  thoracic vertebrae are often fused to form a rigid structure for the scapula to articulate with.  In some species this forms a notarium, a bone ridge across 6 or 8 vertebral spines.

C - Dorsal Vertebrae.  Small in number, about 6 or less, and short, but solid.  These vertebra are also pneumatic and often show a large pneumatic foramen.  In most species, the dorsal vertebrae will have short ribs attached.

D - Sacral Vertebrae.  Usually fused (ankylosed) forming a solid mass of bone and joined firmly to the pelvic bones.  In rhamphorhynchoids this structure is fairly open, but in later species it is a closed structure.  There may be typically between 6 to 10 vertebrae in the sacrum.

E - Caudal Vertebrae.  Present in all pterosaurs, but very few in the pterodactyloids. The caudal vertebrae of Rhamphorhynchus may include over 35 vertebra and each one having two long stiffening rods of bone alongside.

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