Pro`to*ver"te*bra (?), n.; pl.
Protovertebræ . [Proto- +
vertebra.] (Anat.) One of the primitive masses, or
segments, into which the mesoblast of the vertebrate embryo breaks up
on either side of the anterior part of the notochord; a mesoblastic,
or protovertebral, somite. See Illust. of
Ectoderm.
☞ The protovertebræ were long regarded as rudiments of
the permanent vertebræ, but they are now known to give rise to
the dorsal muscles and other structures as well as the vertebral
column. See Myotome.