Opinions from R. A. Martin 1974
- 'Aenocyon is a subjective synonym of Canis'
- 'Allophaiomys is a subjective synonym of Phaiomys'
- 'Allophaiomys pliocaenicus is recombined as Phaiomys pliocaenicus'
- 'Arvicola didelta is recombined as Pitymys dideltus'
- 'Arvicola didelta is a subjective synonym of Pedomys dideltus' according to Hibbard 1955
- 'Arvicola didelta is recombined as Microtus dideltus' according to Cope 1899
- 'Arvicola didelta is recombined as Microtus didelta' according to Cope 1896
- 'Arvicola didelta belongs to Arvicola' according to Cope 1871
- 'Arvicola involuta is recombined as Pitymys involutus'
- 'Arvicola involuta is a subjective synonym of Pedomys dideltus' according to Hibbard 1955
- 'Arvicola involuta belongs to Arvicola' according to Cope 1871
- 'Arvicola speothen is a subjective synonym of Neodon'
- 'Arvicola speothen is recombined as Microtus speothen' according to Hibbard 1955
- 'Arvicola speothen is recombined as Microtus speothen' according to Cope 1899
- 'Arvicola speothen is recombined as Microtus speothen' according to Cope 1896
- 'Arvicola speothen belongs to Arvicola' according to Cope 1871
- 'Canis armbrusteri is a subjective synonym of Canis lupus'
- 'Canis armbrusteri belongs to Canis' according to Gidley 1913
- 'Canis ayersi is a subjective synonym of Canis dirus'
- 'Canis dirus belongs to Canis'
- 'Canis furlongi is a subjective synonym of Canis lupus'
- 'Canis milleri is a subjective synonym of Canis lupus'
- 'Canis occidentalis is a subjective synonym of Canis lupus'
- 'Canis occidentalis belongs to Canis' according to J. Merriam 1912
- 'Hypudaeus ochrogaster is recombined as Pitymys ochrogaster'
- 'Microtus llanensis is recombined as Pitymys llanensis'
- 'Microtus paroperarius is recombined as Neodon paroperarius'
- 'Microtus paroperarius belongs to Microtus' according to Hibbard 1944
- 'Pedomys is a subjective synonym of Pitymys'
- 'Pitymys belongs to Cricetidae'
- 'Pitymys belongs to Cricetidae' according to Miller 1912
- 'Pitymys aratai belongs to Pitymys'
- 'Sigmodon hilli is a subjective synonym of Sigmodon minor' according to Cantwell 1969
- 'Sigmodon hilli is a subjective synonym of Sigmodon minor'
- 'Sigmodon hilli is a subjective synonym of Sigmodon minor' according to R. Martin 1970
- 'Sigmodon intermedius is a subjective synonym of Sigmodon medius'
- 'Sigmodon intermedius is a subjective synonym of Sigmodon medius' according to Hibbard 1972
- 'Sigmodon intermedius is a subjective synonym of Sigmodon medius' according to R. Martin 1970
- 'Sigmodon intermedius belongs to Sigmodon' according to Hibbard 1937