Thoracic Vertebrae

These can be up to twelve in some species, but there are usually less than this.  Rhamphorhynchoids have distinct thoracic vertebrae that are separately developed.  In Pterodactyloids, the thoracic vertebrae are usually fused to form a rigid structure for the scapula to articulate with.  In most species this forms a notarium, a bone ridge across 5 to 8 dorsal processes.  These vertebrae are pneumatic and they all have rib attachments.

It is unusual to find thoracic vertebrae in isolation.  As they are ankylose and usually fused to a notarium, they tend to be preserved in groups.


The thoracic vertebrae of Rhamphorhynchus are simple in form and articulate to a small degree, allowing some movement.  The ribs were attached on transverse processes.  The scapulo-coracoid was attached to the ribs and vertebrae by ligaments.

With a degree of movement in the spine, a long tail is essential to stabilise the animal in flight.


The thoracic vertebrae of Coloborhynchus form an ankylose block with most of the dorsal processes fused to form a structure called a notarium.

Many medium size pterosaurs have this type of structure, where the scapulo-coracoid joins the dorsal processes of the vertebrae to form the pectoral girdle which supports the wings.


The notarium is fully developed in Pteranodon.  It forms from the dorsal processes of the vertebrae, fused into a bony ridge that has a distinct socket for the scapulo-coracoid bone to articulate with.

This development allowed pteranodon to have a solid pectoral girdle which provided a firm supporting box for the muscles and wings during flight.

 


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