The atlas-axis complex of the mammal-like reptiles
Article first published online: 20 AUG 2009
Journal of Zoology
Volume 159, Issue 2, pages 223–248, October 1969
How to Cite
Kemp, T. S. (1969), The atlas-axis complex of the mammal-like reptiles. Journal of Zoology, 159: 223–248. doi: 10.1111/j.1469-7998.1969.tb03079.x
- Issue published online: 20 AUG 2009
- Article first published online: 20 AUG 2009
- Accepted 8 April 1969
The atlas-axis complexes of four of the major groups of the mammal-like reptiles are discussed. These represent the four principal types of occipital condyle found in the Synapsida: hemispherical in the pelycosaurs, kidney-shaped in the gorgonopsids, trefoil-shaped in the dicynodonts and double in the cynodonts. In each case the possible movements of the skull are analysed in detail. It is shown that the central theme of the wide variation of this structure found within the synapsid reptiles is the manner in which the problem of achieving rotation of the head about a longitudinal axis was solved.
An attempt is made to elucidate the functional evolution of the atlas-axis complex within these reptiles and the significance of the differences between the reptilian and the mammalian complexes is noted.