Epipharyngeal groove

The epipharyngeal groove is a ciliated groove along the dorsal side of the inside of the pharynx in some plankton-feeding early chordates, such as Amphioxus. It helps to carry a stream of mucus with plankton stuck in it, through the pharynx into the gut to be digested.{{cite book|title=Hyman's Comparative Vertebrate Anatomy|author1=Hyman, L.H.|author2=Wake, M.H.|date=1992|publisher=University of Chicago Press|isbn=9780226870137|url=https://books.google.com/books?id=VKlWjdOkiMwC|page=71|access-date=2014-12-13}}

The subnotochordal rod or hypochord is a transient structure that appears ventral to the notochord in the heads of embryos of some vertebrates. Its appearance is stimulated by a chemical secreted by the notochord. The subnotochordal rod helps to stimulate development of the dorsal aorta.{{cite journal|journal=Development |volume=127|pages=869–879|url=http://dev.biologists.org/content/127/4/869.full.pdf|date=25 January 2000|title=Endoderm patterning by the notochord: development of the hypochord in Xenopus|author=O. Cleaver, D. W. Seufert and P. A. Krieg|issue=4|pmid=10648245|access-date=2014-12-13}}

There is an opinion that these two structures are homologous.