The Collaborative International Dictionary
Protovertebrae
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
protovertebrae
n. (plural of protovertebra English)