Reply to Hedges et al.:Accurate timetrees do indeed require accurate calibrations

We (1) attempted to establish an evolutionary timescale for land plant evolution utilizing available genome-scale data and a new set of calibrations constraining the age of clades based on critical analysis of paleontologic, phylogenetic (2), and geologic evidence. We explored many factors, such as the inclusion or exclusion of a calibration on the crown embryophyte node and concluded that the living clade of land plants emerged in a middle Cambrian–Early Ordovician interval. Hedges et al. (3) argue that the results of our study are not robust to dating strategies since removal of maximum constraints (maxima) results in significantly older clade age estimates. They … [↵][1]1To whom correspondence may be addressed. Email: h.schneider{at}nhm.ac.uk or phil.donoghue{at}bristol.ac.uk. [1]: #xref-corresp-1-1