The Collaborative International Dictionary
Protovertebra \Pro`to*ver"te*bra\, n.; pl. Protovertebr[ae] . [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.
Note: The protovertebr[ae] were long regarded as rudiments of the permanent vertebr[ae], but they are now known to give rise to the dorsal muscles and other structures as well as the vertebral column. See Myotome.
Wiktionary
n. (context anatomy English) 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.