Movie 1.

The putative skate spiracular organ placode in relation to the geniculate placode and the nearest lateral line placode. A movie created from a series of 27 adjacent transverse histological sections, in a caudal-to-rostral sequence, at the level of the second (hyoid) pharyngeal arch at S24. The series illustrates the location of the putative spiracular organ placode (asterisk) immediately dorsal to the geniculate placode (g), and its distinction from a more dorsal and rostral neurogenic placode (likely the neurogenic pole of the anteroventral lateral line placode), all three apparently giving rise to neuroblasts within a composite ganglion.