The male Solitaire (Pezophaps) has large bony excrescences on the wrist which may, like spurs, have been sheathed in horn and used for fighting.
Teeth do not occur in any living birds, but conical teeth imbedded in separate sockets are present in Archaeopteryx and Ichthyornis, while in Hesperornis similar teeth occur implanted in continuous grooves in the mandibles and maxillae, the premaxillae being toothless.
Except that teeth are partly dermal in origin, a dermal exoskeleton is quite unrepresented in birds.
ENDOSKELETON.
Perhaps the most striking feature of the endoskeleton of birds is its pneumaticity. In the embryo all the bones contain marrow, but as growth proceeds this becomes replaced by air to a variable extent in different forms. In all birds some part of the skeleton is pneumatic. Many small birds and Apteryx and Penguins among larger ones have air only in the skull; in Pigeons air is present in all the bones except the caudal vertebrae, the leg bones, and those of the antibrachium and manus; in Hornbills every bone contains air.
Fig. 62. Third Cervical Vertebra of an Ostrich (Struthio camelus).
× 1. A anterior, B posterior, C dorsal view (A and B after Mivart).
| 1. neural spine. | 6. anterior articular surface of |
| 2. neural canal. | centrum. |
| 3. prezygapophysis. | 7. vertebrarterial canal. |
| 4. postzygapophysis. | 8. hypapophysis. |
| 5. posterior articular surface of | |
| centrum. |