intercentrum

An intercentrum is a skeletal element of the vertebral column found in some vertebrates, particularly in early tetrapods and in certain amphibians. It is one of the historic components that can contribute to the formation of the vertebral centrum, the main body of a vertebra, with the other component traditionally being the pleurocentrum.

In evolutionary terms, many fossil and some modern amphibians retain a distinct intercentrum as part of the vertebral body. In contrast, most amniotes (reptiles, birds, and mammals) show a vertebral centrum that is formed predominantly from the pleurocentrum, with the intercentrum reduced, fused, or absent. The exact pattern varies among groups, and in some taxa the intercentrum may persist as a small cartilaginous or ossified piece associated with the vertebral complex.

Anatomically, the intercentrum contributes to the articulation surfaces that interact with neighboring vertebrae and with rib elements in taxa that possess ribs. It, together with the pleurocentrum, helps to bear loads and distribute stresses through the spinal column. Developmentally, the intercentrum arises from sclerotome-derived mesenchyme and ossifies endochondrally in taxa where it is present; its presence or absence is an important criterion in comparative anatomy and paleontology.

The term intercentrum derives from Latin roots meaning “between the center,” reflecting its position relative to other vertebral elements. Its study informs discussions on vertebral evolution, the origin of the vertebral centrum, and the anatomical diversity observed across vertebrates.