STASIS NOT CHANGE. “Paedomorphosis, the retention of ‘child-like’ larval or juvenile forms (like the external filamentous gills of aquatic salamanders), is yet another way in which organismal features are retained rather than changed, and another way in which the interactions of phylogeny and ontogeny are reflected in their mutual history.”
https://evolution-outreach.springeropen.com/articles/10.1186/s12052-014-0012-5