Coronodon: another wannabe mysticete ancestor

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.

Figure 1. Coronodon, was originally considered a toothed mysticete, but only in the absence of desmostylians, the real ancestors of mysticetes.

Figure 1. Coronodon, was originally considered a toothed mysticete, but only in the absence of desmostylians, the real ancestors of mysticetes. This taxon lies at the base of Odontoceti and Aetioceti in the LRT.

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.

Figure 2. The nesting of Eocene Andrewsiphius basal to extant tenrecs between leptictids and pakicetids.

Figure 2. The nesting of Eocene Andrewsiphius basal to extant tenrecs between leptictids and pakicetids.

The LRT ancestors to mysticetes
are shown below:

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 3. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale. Key post-crania is missing here, but the skulls tell the tale.

References
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

wiki/Aetiocetus
wiki/Coronodon

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