FIGURE 1.

In this figure, we present a staging series for embryonic Xenopus tropicalis. Stages were broken into four major modules: cleavage, gastrulation, neurulation, and tailbud stages. Both animal and lateral views are shown to highlight the appearance of animal blastomeres as well as the pigment distinctions between animal and vegetal blastomeres. Gastrulation is shown as a continuum from stages 9 to 12.5. Neurulation comprises stages 13 to 18, and staging of this process is primarily predicted from lateral proximity of neural folds to one another in the dorsal view and closure of neural folds in the anterior view. When the neural fold finishes zippering, the embryo begins to elongate. During early tailbud stages (19–24) the embryo develops morphologically well-defined anterior structures including the pharyngeal arches, sensory placodes, and eyecup, while elongating along the anterior-posterior axis. Elongation, development of tail fin, resecting of gut, and development of refined organs then takes place over the rest of tailbud and early tadpole development. The lateral view is best used for staging by looking at the gut morphology, eye morphology, and body elongation. The dorsal view is best used to look at development of arches and elongation