Geisler et al. 2017
presented Coronodon as a recent addition to the panoply of toothed whales said to be ancestral to mysticetes. Taxon exclusion is once again the problem. The real ancestors of mysticetes (Fig. 3) are mesonychids, hippos, anthracobunids and desmostylians, as we learned earlier. These taxa were not tested by Geisler et al. 2017.
Coronodon havensteini (Geisler et al., 2017; early Oligocene, 30 mya) was originally and is traditionally considered a mysticete whale, basal to baleen whales like Balaenoptera. With more tested taxa here it nests basal to odontocete whales like Aetiocetus and Physeter. The archaeocete teeth were considered the first stage in filter-feeding. Here they are relics from an archaeocete ancestry. Descendants in both branches (aetiocetes, odontocetes) both have simple peg teeth.
The LRT ancestors to mysticetes
are shown below:
Geisler JH; Boessenecker RW; Brown M; Beatty BL 2017. The origin of filter feeding in whales. Current Biology. 27 (13): 2036–2042.e2. doi:10.1016/j.cub.2017.06.003