Fig. 1

The early E13.5 embryo as an example. a Planes 1–7 were established at about 100 μm intervals along the anterior–posterior (AP) axis in the median sagittal view. P1 was set at the position where the PSs initially emerged, and P6 was the border where the tongue separated from the lingual frenulum. b The coronal view of the PS and tongue before elevation at early E13.5. The empty arrow indicated the genioglossus. P, palate; T, tongue; M, molar; M, medial; L, lateral