. Chordate morphology. Morphology (Animals); Chordata. and bulkier on the posterior vertebrae of this series. The transverse process has a distinct posterodorsal muscular process, which, on the lumbar vertebrae, becomes separate, lying ventrolateral to the postzygapophysis. In their development, the thoracic vertebrae arise from five ossification centers: bilateral neural arches, vifhich bear the zygapophyses, transverse processes, and the articular facets for the two heads of each rib; and the centrum with its two epiphyses. The lumbar vertebrae have an anteriorly directed neural spine and la
. Chordate morphology. Morphology (Animals); Chordata. and bulkier on the posterior vertebrae of this series. The transverse process has a distinct posterodorsal muscular process, which, on the lumbar vertebrae, becomes separate, lying ventrolateral to the postzygapophysis. In their development, the thoracic vertebrae arise from five ossification centers: bilateral neural arches, vifhich bear the zygapophyses, transverse processes, and the articular facets for the two heads of each rib; and the centrum with its two epiphyses. The lumbar vertebrae have an anteriorly directed neural spine and large pre- and postzygapophyses. The transverse process is lacking, but its posterior process is well developed. In its development, this type of vertebra is like the thoracic. There are three sacral vertebrae in the cat; the most an- terior one is the main support for the pelvic girdle. The transverse process of this anterior sacral is very thickened and distally spread out to suture with the ilium. The sec- ond sacral has a thick transverse process that joins in sup- porting the ilium. The third sacral is not involved. In their development, the sacrals are like the thoracics, except the transverse process of the first sacral includes a secondary center, a costal or rib element, arising below it, and forming much of the articulation with the ilium. The neural canal continues posteriorly through the first seven caudals and then is lost. The pre- and postzyga- pophyses are present, as are anterior and posterior extensions of the transverse process. The fourth to ninth caudals have small "hemal arches" enclosing the caudal artery and vein. These arches are directed forward and serve for muscular attachment. Further posteriorly, the hemal (or haemal) arch is represented by bilateral splints. Embryological development The terminology of the parts of the developing vertebra is quite confusing, because it is based on that of Gadow, who originally applied it to fish vertebrae.
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