Opinions from G. G. Simpson 1932
- 'Desmostylidae belongs to Desmostyliformes'
- 'Desmostyliformes belongs to Sirenia'
- 'Desmostylus belongs to Desmostylidae'
- 'Dugong belongs to Dugonginae'
- 'Dugongidae belongs to Trichechiformes'
- 'Dugonginae belongs to Dugongidae'
- 'Eotheroides belongs to Prorastomidae'
- 'Felsinotherium belongs to Halitheriinae'
- 'Felsinotherium gunteri belongs to Felsinotherium'
- 'Felsinotherium ossivallense belongs to Felsinotherium'
- 'Halitheriidae was reranked as the family Halitheriinae and belongs to Dugongidae'
- 'Halitherium belongs to Halitheriinae'
- 'Hesperosiren belongs to Halitheriinae'
- 'Hesperosiren crataegensis belongs to Hesperosiren'
- 'Hydrodamalidae was reranked as the subfamily Hydrodamalinae and belongs to Dugongidae'
- 'Hydrodamalis belongs to Hydrodamalinae'
- 'Manatherium belongs to Halitheriinae'
- 'Manatus antiquus is a nomen dubium'
- 'Manatus inornatus is a nomen dubium'
- 'Metaxytherium belongs to Halitheriinae'
- 'Metaxytherium floridanum is recombined as Felsinotherium floridanum'
- 'Miosiren belongs to Miosireninae'
- 'Miosireninae belongs to Dugongidae'
- 'Prorastomidae belongs to Trichechiformes'
- 'Prorastomus belongs to Prorastomidae'
- 'Rytiodinae belongs to Dugongidae'
- 'Rytiodus belongs to Rytiodinae'
- 'Thalattosiren belongs to Halitheriinae'
- 'Trichechiformes belongs to Sirenia'
- 'Trichecidae is corrected as Trichechidae and belongs to Trichechiformes'