Diminution of pharyngeal segmentation and the evolution of the amniotes

Segmental and post-segmental stages of pharyngeal development in human embryos. In this figure High-Resolution Episcopic Microscopy (HREM) data from the human embryos from the DMDD website (https://dmdd.org.uk/) is shown. a At Carnegie Stage (Cs) 13, the first three most anterior pharyngeal arches have formed and are morphologically evident. b By Cs 15 stage, a further fourth arch has formed. c However, by Cs16 the segmental nature of the pharyngeal region has been lost as the second arch has overgrown the posterior arches, covered and subsumed them. Scale bar？=？0.25？m