Opinions from R. A. Stirton 1935
- 'Agnotocastor belongs to Castoridae'
- 'Agnotocastor praetereadens belongs to Agnotocastor'
- 'Canis vafer is recombined as Vulpes vafer'
- 'Castor (Eucastor) tortus is recombined as Eucastor tortus'
- 'Castor (Eucastor) tortus is recombined as Eucastor tortus' according to Matthew 1902
- 'Castor (Eucastor) tortus is recombined as Eucastor tortus' according to Allen 1877
- 'Castor peninsulatus is recombined as Palaeocastor peninsulatus'
- 'Dipoides curtus is recombined as Monosaulax curtus'
- 'Eucastor dividerus belongs to Eucastor'
- 'Eucastor planus belongs to Eucastor'
- 'Euhapsis gaulodon is a subjective synonym of Palaeocastor simplicidens'
- 'Hystrix (Hystricops) was reranked as Hystricops and belongs to Castoridae'
- 'Hystrix (Hystricops) venustus is recombined as Hystricops venustus'
- 'Monosaulax belongs to Castoridae'
- 'Palaeocastor magnus is a subjective synonym of Palaeocastor fossor'
- 'Palaeocastor major is a subjective synonym of Palaeocastor fossor'
- 'Palaeocastor major belongs to Palaeocastor'
- 'Protohippus ansae is recombined as Calippus ansae'
- 'Protohippus placidus is recombined as Calippus placidus'
- 'Sigmogomphius is a subjective synonym of Dipoides' according to Matthew 1913
- 'Sigmogomphius belongs to ' according to J. Merriam 1896
- 'Sigmogomphius lecontei is recombined as Eucastor lecontei'
- 'Sigmogomphius lecontei is recombined as Dipoides lecontei' according to Matthew 1913
- 'Sigmogomphius lecontei belongs to Sigmogomphius' according to J. Merriam 1896
- 'Steneofiber barbouri is recombined as Palaeocastor barbouri'
- 'Steneofiber brachyceps is a subjective synonym of Palaeocastor simplicidens'
- 'Steneofiber complexus is recombined as Monosaulax complexus'
- 'Steneofiber fossor is recombined as Palaeocastor fossor'
- 'Steneofiber gradatus is recombined as Palaeocastor gradatus'
- 'Steneofiber hesperus is recombined as Monosaulax hesperus'
- 'Steneofiber montanus is recombined as Agnotocastor montanus'
- 'Steneofiber nebrascensis is recombined as Palaeocastor nebrascensis'
- 'Steneofiber nebrascensis is recombined as Palaeocastor nebrascensis' according to Leidy 1869
- 'Steneofiber pansus is recombined as Monosaulax pansus'
- 'Steneofiber sciuroides is a subjective synonym of Palaeocastor simplicidens'
- 'Steneofiber simplicidens is recombined as Palaeocastor simplicidens'