pleurocentra

Pleurocentra are one of the components that can form the vertebral centrum, the central mass of a vertebra, in various jawed vertebrates. In many early fishes and amphibians, the centrum develops from more than one ossification center, including the pleurocentrum and the intercentrum. The term distinguishes these elements from other parts of the vertebra.

In standard terminology, the pleurocentrum is considered the lateral or dorsal portion of the centrum, while the intercentrum lies ventrally or anteriorly. Together, pleurocentra and intercentra contribute to the full body of the centrum and provide articulation surfaces for the neural arch and, in many taxa, for ribs. The exact contribution of each center varies among lineages and can be a useful character in comparative anatomy and paleontology.

Across vertebrates, the relative prominence of pleurocentra versus intercentra differs. In many amniotes, the pleurocentrum becomes the primary body of the centrum, and the intercentrum is reduced or incorporated into the ventral wall or discarded. In other groups, both centers persist and fuse to form the final centrum, or the intercentrum remains a distinct element in the vertebral articulations. In some fishes and primitive tetrapods, the vertebral centrum may be built largely from pleurocentra, intercentra, or a combination of both.

Development and evolution: ossification centers appear early in vertebral development, and their patterns of fusion can inform phylogenetic relationships among extinct and living lineages. The term pleurocentrum reflects historical, comparative anatomy usage to describe the multi-part nature of the vertebral centrum. Etymology: from pleuron, side, and centrum, center.