Fig. 4.

Map of developing pectoral motor nucleus in rh8-spinal compartment of basal and derived groups of actinopterygian fish (A and B, dorsal views). (A) Craniovertebral junction (asterisk) in postlarval, juvenile midshipman fish cleared and stained with alcian blue and alizarin red. (B) Demarcation of rh8-spinal boundary (yellow hatching) in zebrafish hoxb4a enhancer trap line. (C) Alignment of myotomes (“M”), occipital (Oc1, Oc2), and spinal (Sp1, Sp2) nerves and pectoral (red) and occipital (gray) motoneurons. Phylogeny of study species is also shown (Right). (Adapted from ref. 13.)