Tokarahia kauaeroa (Boessenecker and Fordyce 2015a; Late Oligocene; OU 2235), is known from a long, flat skull and mandibles along with much of the anterior vertebral set. The eyes are set far back in the skull. The nares are elongated.

Wahaora ruwhenua (Boessenecker and Fordyce 2015b; Late Oligocene; OU 22044), is a related genus with a narrower skull. These flathead mysticetes are traditionally allied with flat-head odontocetes, like Aetiocetus. Adding taxa shows this is by convergence.

Sitsqwayk cornishorum (Peredo and Uhen 2016) was considered a transitional taxon linking toothy aetiotheres to toothless mysticetes, but only in the absence of desmostylians. Here Sitsqwayk nests between Cetotherium and two other cetotheres, Yamatocetus and Tokarahia. Sitsqwayk has a short rostrum, a convex posterior mandible and a relatively large scapula. The total length was reported as 456 cm, which would make it proportionately much shorter than Cetotherium, based on a common scapula size.

Herpetocetus morrowi (van Beneden 1871; El Adli, Deméré and Boessenecker 2014; late Miocene to early Pleistocene) was a small ("diminutive") rorqual with a long straight rostrum and flat cranium. The premaxillae are expanded toward the cranium. The mandible was straight ventrally.

Eomysticetus carolinensis (Sanders and Barnes 2002; skull not 1.5m in length). This taxon is often promoted as the most basal baleen whale when workers mistakenly consider the clade Cetacea monophyletic. Note the long pair of nasals.

Maiabalaena nesbittae (Peredo, Pyenson, Marshall and Uhen 2018; USNM 314627, Oligocene, 33mya, Oregon), was originally considered a toothless transitional taxon linking toothed whales to baleen whales. Here Maiabalaena is closely related to Yamatocetus, unrelated to toothed whales.

Micromysticetus rothauseni (Sanders and Barnes 2002; late Oligocene; holotype ChM PV4844) was originally considered a primitive cetioteriid mysticete, but here nests as a derived cetiotherid mysticete with Yamatocetus (below).

Yamatocetus canaliculatus (Okazaki 2012, KMNH VP 000,017, Kitakyushu Museum of Natural History and Human History; latest Early Oligocene) was a mysticete with an overbite. The ribs were double-headed and inflexible, as in terrestrial taxa. The forelimb is hydropedal.The cervical series was longer than in most mysticetes.