Deconstructing the dogma of fore and hindlimb serial homology: evidence from regenerative, developmental, comparative, paleontological and evolutionary studies (919.3)

Abstract

Most textbooks and papers state that the structures of the tetrapod fore‐ and hindlimb are serial homologues. We provide an updated discussion of this subject based on a literature review and on our regenerative studies of axolotls, developmental studies of tetrapods, and comparative and evolutionary studies of all major vertebrate groups, including recent re‐analyses of the appendicular muscles of chondrichthyans, dipnoans and coelacanths. The integrative analysis of the data available strongly supports the idea that the similarity of muscles and bones of the fore and hindlimbs of tetrapods such as salamanders and modern humans is not due to serial homology, but is instead the result of independent evolutionary changes (homoplasy) due to a complex interplay between developmental, functional, topological and phylogenetic constraints. It also offers new insights about the ancestral Bauplan and morphogenetic gradients of tetrapod limbs, including the striking similarity of the zeugopodial (forearm/leg) and autopodial (hand/foot) muscles of the two limbs and ventro‐dorsal symmetry of the zeugopodial muscles of a same limb, about the marked differences between pelvic and pectoral girdle structures, about homeotic transformations related to the number/identity of the digits and associated soft tissue changes, about limb birth defects, and about the differences between limb ontogeny and regeneration.Grant Funding Source: Faculty Start‐Up Package, Howard University College of Medicine