Fig. 15.

Schematic illustrations demonstrating structural similarities in the developing scales of (A) Tremataspis (Osteostraci, Silurian), determined from a rare growth series (Denison, 1947), and (B) Polypterus senegalus (Actinopterygii, Extant); polypteroid-type ganoid scale (after Sire, 1989). Scale bars: A = 250 µm; B = 200 µm.