Before our rapidly increasing knowledge of gene interactions can be connected with the morphologic defects in mutant zebrafish, the normal course of skeletal development must be understood. Here, we describe the developmental morphology of the axial skeleton of zebrafish and review it in relation to the morphology of related species. The relative sequence of ossification in the skeleton is described. Two separate centers of development were found in the axial skeleton (Weberian apparatus and caudal fin) in contrast to tetrapods, which have a single anterior center. Slight variation was found in the overall relative timing of development. The extensive ichthyological literature on teleost anatomy and recent genetic data form the basis for our review and interpretation of homologies of various elements of the axial skeleton. Because homology forms the basis for all evolutionary comparisons, these data are critical for integration in evo-devo studies. Copyright 2003 Wiley-Liss, Inc.
