Figure 4

Divergence time estimation of lancelets based on penalized likelihood (PL) method. Time tree from semiparametric rate smoothing (penalized likelihood, PL) based on the BI tree (Fig. 3). Scale bar shows time scale resulting from calibration using the divergence time between Cephalochordata and Vertebrata (+ Urochordata) (891 Mya) and between Agnatha (Cyclostome) and Gnathostomes (Chondrichthys) (652 Mya) [1]. Arrows indicate calibration point (open head), divergence time between A. inferum and A. lucayanum complex (red solid head), and first appearance of large whales (black solid head).