A review of molecular and morphological data". To read the PDF file, please refer to P. Laurenti (firstname.lastname@example.org).
Title and legend are as follows: Pre-hatching dogfish (Scyliorhinus canícula) embryo stained with alcyan blue (cartilage) and alizarine red (prismatic calcified cartilage), from top to bottom: lateral, dorsal, and ventral view.
These images demonstrate the fate of skeletal elements derived from serially homologous structures which show nested Hox expression: the somites produce only two types of vertebrae (monospondylous and diplospondylous), whereas the branchial arches form a series of differentiated cartilaginous elements (mandibular, hyoid and pharygeals). See Oulion et al. (pp 247-259 of this issue). Embryos stained by Mélanie Debiais-Thibaud, photographed by Patrick Laurenti.