Fig. 4

Fossil calibrated phylogeny and ancestral state reconstruction based on the most supported topology. Letters (a–d) at nodes indicate calibration points. Blue bars at nodes represent standard deviation of age estimation. Red and black bars at nodes represent probabilities of the common ancestor being photosymbiotic (red) or non-photosymbiotic (black). The grey shading in the background corresponds to number of global reef sites through time (following [28])