Notarium is a term used for the fused vertebra of the shoulder in bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s and some pterosaur

Pterosaur

Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...

s. The structure helps brace the chest

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...

 against the forces generated by the wings. In birds, the vertebrae are only in contact with adjacent vertebrae and ribs, while in some pterosaurs the notarium articulates with the scapula. This joint is unique among tetrapods, as in no other taxa is there a direct connection between the pectoral girdle and vertebral column (though in species with clavicles, the clavicle articulates with the sternum, which in turn is connected to the vertebrae via the ribs, allowing an indirect connection).

External links

http://www.palaeos.com/Vertebrates/Lists/Glossary/GlossaryN.html
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1169399/pdf/janat00215-0050.pdf
http://archosaurmusings.wordpress.com/2009/06/05/a-pelvis-at-the-front-the-notarium/