Fig. 7From: On the origin of vertebrate somitesA new evolutionary scenario of the chordate somite formation. a In amphioxus, mesoderm/endoderm boundary formation is organized by Fringe/Delta cassette under Notch signalling. b The Notch signalling-dependent mechanism of segmental boundary formation in (a) was co-opted to the future segments in the anterior PSM of amniotes embryos. The mesoderm is presented in green. The endoderm is in light blue. The dotted line indicates a segmental borderBack to article page