Cover image: Pictured is a 1-day-old larval freshwater pufferfish with the individual first-generation teeth that precede the formation of its characteristic parrot-like “beak.” Gareth J. Fraser et al. found that the pufferfish’s unusual beaked jaw forms via a modified type of continuous tooth addition and replacement. The findings suggest that even highly derived morphological structures such as the pufferfish beak can be formed by an ancient but conserved developmental plan. See the article by Fraser et al. on pages 8179–8184. Image courtesy of Ralf Britz.