Fig. 6
From: Acoel regeneration mechanisms indicate an ancient role for muscle in regenerative patterning
Model for evolution of muscle-specific positional control. a Both planarians and Hofstenia demonstrate muscle-specific expression of positional control genes, despite divergence of over 550 million years. b Muscle-specific expression of PCGs in both lophotrochozoans and acoels suggests that it arose as a mechanism of regenerative patterning at the base of the Bilateria, over 550 million years ago
