protovertebra

Century Dictionary and Cyclopedia

1. n. In Carus's nomenclature (1828), a rib regarded as a vertebral element developed to contain and protect the viscera, or organs of vegetative life: correlated with deutovertebra and tritovertebra.
2. n. A primitive, temporary vertebra; one of the series of segments which appear in pairs in the early embryo along the course of the notochord, and from or about which the permanent vertebræ are developed. They soon disappear, being replaced by definitive vertebræ.

Wiktionary

1. n. anatomy 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.

GNU Webster's 1913

1. n. (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.