protovertebra
/ˌprəʊtəʊˈvəːtɪbrə/noun
Embryology. Each of the segments of the embryonic mesoderm which subsequently develop into the vertebrae and associated muscles. Formerly also: †a myotome, regarded as having a similar role ( obsolete ). Now rare.
Origin
Mid 19th century (in an earlier sense). From proto- + vertebra.