hypurapophysis
Lateral process, spine-like or crest-like, at the lateral wall of the haemal arch of the parhypural that serves for insertion of the hypochordal longitudinal muscle. The process may contribute to the lateral protection of the parhypural foramen (where the caudal blood vessels exit the hemal arch) and the hypural foramen (where a caudal heart may be present). The hypurapophysis is paired.