File:EB1911 Reptiles - Composition of Vertebrae of Reptiles.jpg

English: Composition of Vertebrae of Reptiles. In all the figures the right side looks towards the head. 1. Diagram showing the relative position of the four pairs of arcualia which constitute a complete quadripartite vertebra. B.D., Basidorsal; B.V., basiventral; I.D., interdorsal; I.V., interventral, shaded vertically in all figures; N., position of axil of the spinal nerve, i.e. behind the neural arch of its vertebra. 2, 3. Side views of the constituent cartilaginous blocks of a caudal vertebra (2) and a trunk vertebra (3) of Archegosaurus, as typical examples of temnospondylous quadripartite and tripartite vertebrae. For comparison with Reptilian vertebrae. 4. Temnospondylous tripartite vertebra of the trunk of Eryops, a Permian reptile. 5. Composition of the second vertebra of a crocodile. 6. A vertebra of which the vasiventrals are reduced to an “interventrum.” 7. Side view of the first and second cervical vertebra of a crocodile. 8. The same analysed. N1, N2 and N3, position of the first, second and third spinal nerves; S.D., occasionally called Proatlas, the detached spinous process, or supradorsal, of the atlas or first vertebra. 9. The first three vertebrae of Sphenodon. 10. The complete atlas vertebra of an adult Trionyx, still typically temnospondylous.