Opinions from O. Abel 1919
- 'Acrodelphidae belongs to Squaloceti'
- 'Acrodelphis belongs to Acrodelphidae'
- 'Agorophiidae belongs to Archaeoceti'
- 'Agorophius belongs to Agorophiidae'
- 'Agriocetus belongs to Patriocetidae'
- 'Anoplonassa belongs to Ziphiidae'
- 'Archaeoceti belongs to Cetacea'
- 'Archaeosiren belongs to Miosireninae'
- 'Argyrocetus belongs to Acrodelphidae'
- 'Aulocetus belongs to Balaenopteridae'
- 'Balaena belongs to Balaenidae'
- 'Balaenopteridae belongs to Mystacoceti'
- 'Balanadae is corrected as Balaenidae and belongs to Mystacoceti'
- 'Barytheriidae belongs to Proboscidea'
- 'Barytherium belongs to Barytheriidae'
- 'Cetacea belongs to Mammalia'
- 'Cetotherium belongs to Balaenopteridae'
- 'Choneziphius belongs to Ziphiidae'
- 'Cyrtodelphis belongs to Acrodelphidae'
- 'Deinotheriidae is corrected as Dinotheriidae and belongs to Proboscidea'
- 'Deinotherium is corrected as Dinotherium and belongs to Dinotheriidae'
- 'Delphinoceti belongs to Cetacea'
- 'Delphinodon belongs to Delphinoceti'
- 'Delphinus belongs to Delphinoceti'
- 'Desmostylidae belongs to Proboscidea'
- 'Elephantidae belongs to Proboscidea'
- 'Eocetus belongs to Zeuglodontidae'
- 'Eosiren belongs to Halitheriinae'
- 'Eurhinodelphidae belongs to Squaloceti'
- 'Eurhinodelphis belongs to Eurhinodelphidae'
- 'Felsinotherium belongs to Halitheriinae'
- 'Halicore belongs to Halicorinae'
- 'Halicoridae belongs to Sirenia'
- 'Halicorinae belongs to Halicoridae'
- 'Halitheriidae was reranked as the family Halitheriinae and belongs to Halicoridae'
- 'Halitherium (Prototherium) was reranked as Prototherium and belongs to Halitheriinae'
- 'Kekenodon belongs to Zeuglodontidae'
- 'Manatherium belongs to Manatidae'
- 'Manatidae belongs to Sirenia'
- 'Manatus belongs to Manatidae'
- 'Mastodon belongs to Elephantidae'
- 'Mesoplodon belongs to Ziphiidae'
- 'Metaxytherium belongs to Halitheriinae'
- 'Microzeuglodon belongs to Microzeuglodoptidae'
- 'Microzeuglodontidae [misspelled as Microzeuglodoptidae] belongs to Archaeoceti'
- 'Miosiren belongs to Miosireninae'
- 'Miosireninae belongs to Halicoridae'
- 'Mioziphius belongs to Ziphiidae'
- 'Moeritheriidae belongs to Proboscidea'
- 'Moeritherium belongs to Moeritheriidae'
- 'Mystacoceti belongs to Cetacea'
- 'Neosqualodon belongs to Squalodontidae'
- 'Pachyacanthus belongs to Balaenopteridae'
- 'Palaeomastodon belongs to Palaeomastodontidae'
- 'Palaeomastodontidae belongs to Proboscidea'
- 'Palaeophocaena belongs to Delphinoceti'
- 'Palaeoziphius belongs to Ziphiidae'
- 'Patriocetidae belongs to Archaeoceti'
- 'Patriocetus belongs to Patriocetidae'
- 'Physeter belongs to Physeteridae'
- 'Physeteridae belongs to Squaloceti'
- 'Physeterula belongs to Physeteridae'
- 'Pinnipedia belongs to Mammalia'
- 'Pithanodelphis belongs to Delphinoceti'
- 'Placoziphius belongs to Physeteridae'
- 'Plagiosauridae belongs to Rhachitomi'
- 'Plesiocetus belongs to Balaenopteridae'
- 'Prophyseter belongs to Physeteridae'
- 'Prorastomus belongs to Manatidae'
- 'Prosqualodon belongs to Agorophiidae'
- 'Protocetus belongs to Zeuglodontidae'
- 'Protophocaena belongs to Delphinoceti'
- 'Protosiren belongs to Miosireninae'
- 'Prozeuglodon belongs to Zeuglodontidae'
- 'Rhytina belongs to Halicorinae'
- 'Rytiodus is corrected as Rhytiodus and belongs to Halitheriinae'
- 'Saurodelphis belongs to Acrodelphidae'
- 'Scaldicetus belongs to Physeteridae'
- 'Sirenia was reranked as a order and belongs to Mammalia'
- 'Squaloceti belongs to Cetacea'
- 'Squalodon belongs to Squalodontidae'
- 'Squalodontidae belongs to Squaloceti'
- 'Stegodon belongs to Elephantidae'
- 'Zeuglodon belongs to Zeuglodontidae'
- 'Zeuglodontidae belongs to Archaeoceti'
- 'Ziphiidae was reranked as the tribe Ziphiina and belongs to Squaloceti'