Opinions from K. A. Zittel 1925
- 'Acrodelphidae belongs to Odontoceti'
- 'Acrodelphinae belongs to Acrodelphidae'
- 'Acrodelphis belongs to Acrodelphidae'
- 'Archaeoceti belongs to Cetacea'
- 'Arctocephalus belongs to Otariidae'
- 'Argyrocetinae belongs to Acrodelphidae'
- 'Argyrocetus belongs to Argyrocetinae'
- 'Arionius is a subjective synonym of Squalodon'
- 'Aulocetus is a subjective synonym of Cetotherium'
- 'Balaena belongs to Balaenidae'
- 'Balaenodon is a subjective synonym of Scaldicetus'
- 'Balaenoptera belongs to Balaenopteridae'
- 'Balaenopteridae belongs to Mystacoceti'
- 'Balanadae is corrected as Balaenidae and belongs to Mysticeti'
- 'Basilosaurus is a subjective synonym of Zeuglodon'
- 'Belemnoziphius is a subjective synonym of Mesoplodon'
- 'Beluga belongs to Beluginae'
- 'Beluginae belongs to Acrodelphidae'
- 'Berardius belongs to Ziphiinae'
- 'Cetacea belongs to Mammalia'
- 'Cetotherium belongs to Balaenopteridae'
- 'Champsodelphis is a subjective synonym of Palaeoziphius'
- 'Choneziphius belongs to Ziphiinae'
- 'Cyrtodelphis belongs to Argyrocetinae'
- 'Delphinidae belongs to Odontoceti'
- 'Delphinodon is a subjective synonym of Squalodon'
- 'Delphinopsis belongs to Phocaenini'
- 'Delphinopsis freyeri belongs to Delphinopsis'
- 'Delphinus belongs to Delphinidae'
- 'Desmostylus belongs to Sirenia'
- 'Desmostylus hesperus belongs to Desmostylus'
- 'Dioplodon is a subjective synonym of Mesoplodon'
- 'Dorudon is a subjective synonym of Zeuglodon'
- 'Eocetus belongs to Zeuglodontidae'
- 'Eosiren belongs to Sirenia'
- 'Eotherium belongs to Sirenia'
- 'Eucetus is a subjective synonym of Scaldicetus'
- 'Eudelphis is a subjective synonym of Scaldicetus'
- 'Eurhinodelphidae belongs to Odontoceti'
- 'Eurhinodelphis belongs to Eurhinodelphidae'
- 'Felsinotherium belongs to Sirenia'
- 'Felsinotherium forestii belongs to Felsinotherium'
- 'Globicephala is corrected as Globicephalus and belongs to Delphinidae'
- 'Halianassa is a subjective synonym of Halitherium'
- 'Halicore belongs to Sirenia'
- 'Halicore cuvierii is recombined as Metaxytherium cuvieri'
- 'Halitherium belongs to Sirenia'
- 'Halitherium christolii is corrected as Halitherium christoli and belongs to Halitherium'
- 'Halitherium serresii is recombined as Metaxytherium serresi'
- 'Halitherium veronense belongs to Halitherium'
- 'Herpetocetus belongs to Balaenopteridae'
- 'Heterocetus belongs to Balaenopteridae'
- 'Heterodelphis belongs to Acrodelphinae'
- 'Heterodelphis leiodontus belongs to Heterodelphis'
- 'Homaeocetus is a subjective synonym of Scaldicetus'
- 'Hoplocetus is a subjective synonym of Scaldicetus'
- 'Hyperoodon belongs to Ziphiinae'
- 'Inia belongs to Iniinae'
- 'Iniinae belongs to Acrodelphidae'
- 'Ischyrorhynchus belongs to Argyrocetinae'
- 'Ixacanthus belongs to Acrodelphinae'
- 'Kekenodon omata is an invalid subgroup of Squalodontidae'
- 'Kogia belongs to Physeterinae'
- 'Leptophoca belongs to Phocidae'
- 'Lobodon belongs to Phocidae'
- 'Lophocetus belongs to Acrodelphinae'
- 'Manatherium belongs to Sirenia'
- 'Manatus belongs to Sirenia'
- 'Mesocetus belongs to Balaenopteridae'
- 'Mesocetus is an objective synonym of Eocetus'
- 'Mesoplodon belongs to Ziphiinae'
- 'Mesoteras belongs to Balaenopteridae'
- 'Metaxytherium belongs to Sirenia'
- 'Metaxytherium krahuletzi belongs to Metaxytherium'
- 'Miosiren belongs to Sirenia'
- 'Mioziphius belongs to Ziphiinae'
- 'Monachus belongs to Phocidae'
- 'Monodon belongs to Beluginae'
- 'Monotherium is corrected as Monatherium and belongs to Phocidae'
- 'Mystacoceti belongs to Cetacea'
- 'Neosqualodon belongs to Squalodontidae'
- 'Neosqualodon assenzae belongs to Neosqualodon'
- 'Odontoceti belongs to Cetacea'
- 'Orca belongs to Delphinidae'
- 'Otaria belongs to Otariidae'
- 'Otariina was reranked as the family Otariidae and belongs to Pinnipedia'
- 'Pachyodon is a subjective synonym of Squalodon'
- 'Palaeodelphis is a subjective synonym of Scaldicetus'
- 'Palaeophocaena belongs to Phocaenini'
- 'Palaeoziphius belongs to Ziphiinae'
- 'Paleophoca is corrected as Palaeophoca and belongs to Phocidae'
- 'Pappocetus belongs to Zeuglodontidae'
- 'Phoca belongs to Phocidae'
- 'Phoca ambigua is an invalid subgroup of Squalodontidae'
- 'Phoca holitschensis belongs to Phoca'
- 'Phoca pontica belongs to Phoca'
- 'Phoca vindobonensis belongs to Phoca'
- 'Phocadae is corrected as Phocidae and belongs to Pinnipedia'
- 'Phocaenina is corrected as Phocaenini and belongs to Delphinidae'
- 'Phocaenopsis is a subjective synonym of Acrodelphis'
- 'Phocodon is a subjective synonym of Squalodon'
- 'Physeter belongs to Physeterinae'
- 'Physeteridae belongs to Odontoceti'
- 'Physeterinae belongs to Physeteridae'
- 'Physeterula belongs to Physeterinae'
- 'Physodon is a subjective synonym of Scaldicetus'
- 'Pinnipedia was reranked as a suborder and belongs to Carnivora'
- 'Pithanodelphis belongs to Delphinidae'
- 'Placoziphius is a subjective synonym of Mioziphius'
- 'Platanista belongs to Iniinae'
- 'Plesiocetus belongs to Balaenopteridae'
- 'Pontistes belongs to Iniinae'
- 'Pontivaga belongs to Argyrocetinae'
- 'Pontobasileus is a nomen vanum'
- 'Pontoleon belongs to Otariidae'
- 'Pontoporia belongs to Iniinae'
- 'Priscodelphinus is a subjective synonym of Eurhinodelphis'
- 'Pristiphoca belongs to Phocidae'
- 'Prohalicore belongs to Sirenia'
- 'Prophoca belongs to Phocidae'
- 'Prophyseter belongs to Physeterinae'
- 'Prorastomus belongs to Sirenia'
- 'Prorastomus sirenoides belongs to Prorastomus'
- 'Prosqualodon belongs to Squalodontidae'
- 'Prosqualodon australis belongs to Prosqualodon'
- 'Prosqualodon davidis is corrected as Prosqualodon davidi and belongs to Prosqualodon'
- 'Protocetus belongs to Zeuglodontidae'
- 'Protocetus atavus belongs to Protocetus'
- 'Protophocaena belongs to Phocaenini'
- 'Protosiren belongs to Sirenia'
- 'Prozeuglodon atrox is a subjective synonym of Zeuglodon isis'
- 'Pseudorca belongs to Delphinidae'
- 'Pugmeodon schinzii is recombined as Halitherium schinzi'
- 'Rhabdosteus belongs to Acrodelphinae'
- 'Rhizoprion is a subjective synonym of Squalodon'
- 'Rhytina belongs to Sirenia'
- 'Rhytina stellerus is corrected as Rhytina stelleri and belongs to Rhytina'
- 'Rytiodus is corrected as Rhytiodus and belongs to Sirenia'
- 'Saurodelphis belongs to Argyrocetinae'
- 'Scaldicetus belongs to Physeterinae'
- 'Siphonocetus belongs to Balaenopteridae'
- 'Sirenia was reranked as a suborder and belongs to Subungulata'
- 'Squalodon belongs to Squalodontidae'
- 'Squalodontidae belongs to Odontoceti'
- 'Steno belongs to Delphinidae'
- 'Subungulata was reranked as a order and belongs to Mammalia'
- 'Thalassocetus belongs to Physeterinae'
- 'Trichechidae belongs to Pinnipedia'
- 'Tursiops belongs to Delphinidae'
- 'Zarhachis belongs to Acrodelphinae'
- 'Zeuglodon belongs to Zeuglodontidae'
- 'Zeuglodon brachyspondylus belongs to Zeuglodon'
- 'Zeuglodon cetoides belongs to Zeuglodon'
- 'Zeuglodon harwoodi is an invalid subgroup of Squalodontidae'
- 'Zeuglodon isis belongs to Zeuglodon'
- 'Zeuglodon osiris belongs to Zeuglodon'
- 'Zeuglodon wanklyni belongs to Zeuglodon'
- 'Zeuglodon zitteli belongs to Zeuglodon'
- 'Zeuglodontidae belongs to Archaeoceti'
- 'Ziphiinae belongs to Physeteridae'
- 'Ziphius belongs to Ziphiinae'