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. Here it nests basal to odontocete whales like Aetiocetus and Chonecetus. 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.

Chonecetus sookensis (Russell 1968; Barnes et al. 1995; belongs to Fucaia Marx et al. 2015) nests with Aetiocetus in the LRT. The small lacrimal (orange) is starting to extend over the frontals, as in Orcinus and Physeter.

Aetiocetus cotylalveus (Emlong 1966; Oligocene, 30 mya) was originally and is traditionally considered a mysticete whale, basal to baleen whales like Balaenoptera. Here it nests with odontocete whales between Zygorhiza and Orcinus. Desmostylians, like Paleoparadoxia, nest closer to the origin of baleen whales.

Considered remarkable for the retention of nutrient foramnina (blood vessel channels in the palatal portion of the maxilla that indicate the presence of baleen tissues)

Janjucetus hunderi (Fitzgerald 2006; late Oligocene; est. 3.5m in length) was originally considered the basalmost Mysticeti (baleen whale), but it had large serration teeth, the whale-like post-crania imnagined by Fitzgerald is supported by phylogenetic bracketing, but this is a relative of Aetiocetus, basal to Odontoceti (toothed whale). The skull was more than twice as wide as tall. The orbit was at mid skull, not in the posterior half, as in related taxa. This is a result of phylogenetic miniaturization and neotony.

Mammalodon colliveri (Pritchard 1939; Late Oligocene, est 3 m in length) was previously considered a basal mysticete with teeth, closely resembling Janjucetus. Here it nests with Janjucetus and archaeocetes leading to odontocetes. The snout is shorter than the cranium.

Mammalodon hakataramea (Fordyce and Marx 2016)