Opinions from W. D. Matthew 1909
- 'Aelurotherium is a subjective synonym of Patriofelis'
- 'Aelurotherium belongs to ' according to Adams 1896
- 'Aelurotherium bicuspis is a subjective synonym of Patriofelis ferox'
- 'Aelurotherium latidens is a subjective synonym of Patriofelis ferox'
- 'Alticamelus giraffinus belongs to Alticamelus'
- 'Alticamelus leptocolon belongs to Alticamelus'
- 'Amphicyon vulpinum is recombined as Miacis vulpinus'
- 'Anchitherium brachylophus is recombined as Mesohippus brachylophus'
- 'Anchitherium condoni is recombined as Miohippus condoni'
- 'Ancodus rostratus is recombined as Hyopotamus rostratus'
- 'Anisacodon is a subjective synonym of Pantolestes'
- 'Anisacodon elegans is recombined as Pantolestes elegans'
- 'Arctomys vetus is recombined as Palaearctomys vetus'
- 'Blastomeryx borealis is recombined as Palaeomeryx borealis'
- 'Canis marshii is recombined as Telmatherium marshii'
- 'Canis vafer is recombined as Tephrocyon vafer'
- 'Castor (Eucastor) tortus is recombined as Dipoides tortus'
- 'Centracodon is a subjective synonym of Entomacodon'
- 'Centracodon delicatus is a subjective synonym of Entomacodon minutus'
- 'Desmatotherium belongs to Ceratomorpha'
- 'Dicrocerus tehuanus is recombined as Merycodus tehuanus'
- 'Didymictis belongs to Viverravidae'
- 'Didymictis is a subjective synonym of Viverravus' according to Wortman 1901
- 'Didymictis dawkinsianus is recombined as Viverravus dawkinsianus'
- 'Didymictis dawkinsianus is recombined as Viverravus dawkinsianus' according to Wortman 1899
- 'Didymictis massetericus is recombined as Uintacyon massetericus'
- 'Didymictis primus is a subjective synonym of Didymictis haydenianus'
- 'Dilophodon belongs to Ceratomorpha'
- 'Dilophodon is a subjective synonym of Helaletes' according to Matthew 1899
- 'Dilophodon minusculus belongs to Dilophodon'
- 'Dilophodon minusculus is recombined as Helaletes minusculus' according to Matthew 1899
- 'Dissacus leptognathus belongs to Dissacus' according to Osborn and Wortman 1892
- 'Dissacus leptognathus is recombined as Hapalodectes leptognathus'
- 'Dromocyon is a subjective synonym of Synoplotherium'
- 'Dromocyon is a subjective synonym of Synoplotherium' according to Wortman 1901
- 'Dromocyon belongs to ' according to Marsh 1876
- 'Dromocyon vorax is recombined as Synoplotherium vorax'
- 'Elomeryx mitis is a nomen dubium'
- 'Entomolestes belongs to Erinaceidae'
- 'Entomolestes grangeri belongs to Entomolestes'
- 'Eohippus pernix belongs to Eohippus'
- 'Eohippus venticolus belongs to Eohippus'
- 'Equus (Protohippus) perditus is recombined as Protohippus perditus'
- 'Equus cumminsii is recombined as Protohippus cumminsii'
- 'Equus eurystylus is recombined as Neohipparion eurystyle'
- 'Equus phlegon is recombined as Protohippus phlegon'
- 'Equus simplicidens is recombined as Pliohippus simplicidens'
- 'Eucrotaphus jacksoni leptacanthus is recombined as Eporeodon leptacanthus'
- 'Gomphotherium cameloides is recombined as Paratylopus cameloides'
- 'Hapalodectes belongs to Hapalodectidae'
- 'Hapalodectes compressus belongs to Hapalodectes'
- 'Harpagolestes immanis belongs to Harpagolestes'
- 'Harpalodon is a subjective synonym of Miacis'
- 'Harpalodon belongs to ' according to Marsh 1872
- 'Harpalodon sylvestris is recombined as Miacis sylvestris'
- 'Harpalodon vulpinus is a subjective synonym of Viverravus gracilis'
- 'Helotherium procyoninum is recombined as Orohippus procyoninus'
- 'Hemipsalodon is a subjective synonym of Pterodon'
- 'Hemipsalodon is a subjective synonym of Pterodon' according to Matthew 1901
- 'Hemipsalodon grandis is a subjective synonym of Pterodon'
- 'Hemipsalodon grandis is a subjective synonym of Pterodon' according to Matthew 1901
- 'Heptacodon is a subjective synonym of Anthracotherium'
- 'Heptacodon armatus is a nomen dubium'
- 'Heptacodon curtus is recombined as Anthracotherium curtum'
- 'Hipparion gratum is recombined as Neohipparion gratum'
- 'Hipparion occidentale is recombined as Neohipparion occidentale'
- 'Hippidium interpolatum is recombined as Protohippus interpolatus'
- 'Hippidium spectans is recombined as Protohippus spectans'
- 'Hippodon speciosus is recombined as Neohipparion speciosum'
- 'Hippotherium ingenuum is recombined as Neohipparion ingenuum'
- 'Hippotherium isonesum is recombined as Merychippus isonesus'
- 'Hippotherium montezumae is recombined as Neohipparion montezuma'
- 'Hippotherium paniense is recombined as Merychippus paniensis'
- 'Hippotherium peninsulatum is recombined as Neohipparion peninsulatum'
- 'Hippotherium plicatile is recombined as Neohipparion plicatile'
- 'Hippotherium rectidens is recombined as Neohipparion rectidens'
- 'Hippotherium relictum is recombined as Neohipparion relictum'
- 'Hippotherium retrusum is recombined as Neohipparion retrusum'
- 'Hippotherium sinclairi is recombined as Neohipparion sinclairi'
- 'Hippotherium sphenodus is recombined as Merychippus sphenodus'
- 'Hyopotamus brachyrhynchus belongs to Hyopotamus'
- 'Hyopsodus acolytus is recombined as Mioclaenus acolytus'
- 'Hyopsodus despiciens belongs to Hyopsodus'
- 'Hyopsodus gracilis is recombined as Smilodectes gracilis'
- 'Hyopsodus lepidus belongs to Hyopsodus'
- 'Hyopsodus minusculus belongs to Hyopsodus'
- 'Hyopsodus minusculus is a subjective synonym of Hyopsodus vicarius' according to Cope 1875
- 'Laopithecus robustus is recombined as Leptochoerus robustus'
- 'Lemuravus is a subjective synonym of Hyopsodus'
- 'Lemuravus is a subjective synonym of Hyopsodus' according to Loomis 1905
- 'Lemuravus distans is a subjective synonym of Hyopsodus paulus'
- 'Leptochoerus quadricuspis is recombined as Stibarus quadricuspis'
- 'Leptomeryx mammifer is recombined as Trigenicus mammifer'
- 'Limnocyon agilis is recombined as Sinopa agilis' according to Matthew 1899
- 'Limnocyon agilis is recombined as Tritemnodon agilis'
- 'Limnocyon agilis is recombined as Tritemnodon agilis' according to Matthew 1906
- 'Limnocyon agilis is recombined as Sinopa agilis' according to Matthew 1901
- 'Limnocyon medius is recombined as Thinocyon medius'
- 'Limnocyon potens belongs to Limnocyon'
- 'Limnocyon protenus is recombined as Didymictis protenus'
- 'Limnocyon protenus belongs to Limnocyon' according to Cope 1874
- 'Limnocyon riparius is a subjective synonym of Limnocyon verus'
- 'Limnocyon riparius is recombined as Telmatocyon riparius' according to Marsh 1899
- 'Limnocyon verus belongs to Limnocyon'
- 'Limnocyon verus is recombined as Sinopa vera' according to Matthew 1901
- 'Limnocyon verus is recombined as Sinopa vera' according to Matthew 1899
- 'Limnofelis is a subjective synonym of Patriofelis'
- 'Limnofelis ferox is recombined as Patriofelis ferox'
- 'Limnofelis latidens is a subjective synonym of Patriofelis ferox'
- 'Limnotherium is a subjective synonym of Notharctus'
- 'Lophiodon modestus is recombined as Isectolophus modestus'
- 'Lophiotherium vasacciense is recombined as Eohippus vasacciensis'
- 'Machaeroides belongs to Oxyaenidae'
- 'Machaeroides eothen belongs to Machaeroides'
- 'Menotherium lemurinum is recombined as Leptochoerus lemurinus'
- 'Merycochoerus altiramus is recombined as Pronomotherium altiramus'
- 'Mesohippus gidleyi is recombined as Miohippus gidleyi'
- 'Mesohippus validus is recombined as Miohippus validus'
- 'Miacis is a subjective synonym of Vulpavus' according to Wortman and Matthew 1899
- 'Miacis belongs to Miacidae'
- 'Miacis is a subjective synonym of Vulpavus' according to Wortman 1901
- 'Miacis bathygnathus is recombined as Uintacyon bathygnathus'
- 'Miacis canavus is recombined as Vulpavus canavus'
- 'Miacis canavus is recombined as Prodaphaenus canavus' according to Wortman 1901
- 'Miacis medius belongs to Miacis'
- 'Miacis parvivorus belongs to Miacis'
- 'Miacis parvivorus is recombined as Vulpavus parvivorus' according to Wortman 1901
- 'Miacis uintensis is recombined as Prodaphaenus uintensis'
- 'Miacis uintensis is recombined as Prodaphaenus uintensis' according to Matthew 1899
- 'Microsus belongs to Artiodactyla'
- 'Microsyops vicarius is a subjective synonym of Hyopsodus paulus'
- 'Mioclaenus etsagicus is recombined as Helohyus etsagicus'
- 'Miolabis (Paratylopus) was reranked as Paratylopus and belongs to Camelidae'
- 'Miolabis (Paratylopus) primaevus belongs to Miolabis (Paratylopus)'
- 'Myolestes belongs to '
- 'Myolestes dasypelix belongs to Myolestes'
- 'Neohipparion whitneyi belongs to Neohipparion'
- 'Neovulpavus washakius is recombined as Miacis washakius'
- 'Nyctilestes is a subjective synonym of Nyctitherium'
- 'Nyctilestes belongs to ' according to Marsh 1872
- 'Nyctilestes serotinum is recombined as Nyctitherium serotinum'
- 'Nyctilestes serotinum belongs to Nyctilestes' according to Marsh 1872
- 'Nyctitherium curtidens belongs to Nyctitherium'
- 'Oodectes proximus belongs to Oodectes'
- 'Oreocyon is a subjective synonym of Patriofelis' according to Matthew 1899
- 'Oreocyon belongs to ' according to Marsh 1872
- 'Oreocyon is a subjective synonym of Patriofelis'
- 'Oreodon coloradoensis belongs to Oreodon'
- 'Orohippus uintensis is recombined as Epihippus uintensis'
- 'Oxyaenodon belongs to Limnocyonidae'
- 'Oxyaenodon belongs to Limnocyonidae' according to Matthew 1899
- 'Oxyaenodon dysodus belongs to Oxyaenodon'
- 'Oxyaenodon dysodus belongs to Oxyaenodon' according to Matthew 1899
- 'Pachyaena belongs to Mesonychidae'
- 'Pachyaena belongs to Mesonychidae' according to Osborn and Wortman 1892
- 'Pachyaena is a subjective synonym of Mesonyx' according to Cope 1884
- 'Pachyaena belongs to Mesonychidae' according to Cope 1874
- 'Pachyaena ossifraga belongs to Pachyaena'
- 'Pachyaena ossifraga belongs to Pachyaena' according to Osborn and Wortman 1892
- 'Pachyaena ossifraga is recombined as Mesonyx ossifraga' according to Cope 1885
- 'Pachyaena ossifraga belongs to Pachyaena' according to Cope 1874
- 'Palaearctonyx belongs to Miacidae'
- 'Palaearctonyx meadi belongs to Palaearctonyx'
- 'Pantolestes intermedius belongs to Pantolestes'
- 'Pantolestes longieundus is corrected as Pantolestes longicaudus and belongs to Pantolestes'
- 'Pantolestes longieundus is recombined as Tomitherium longicaudum' according to Cope 1873
- 'Pantolestes natans belongs to Pantolestes'
- 'Pantolestes phocipes belongs to Pantolestes'
- 'Paramys relictus is recombined as Prosciurus relictus'
- 'Paramys robustus is recombined as Pseudotomus robustus'
- 'Passalacodon is a subjective synonym of Pantolestes'
- 'Passalacodon belongs to ' according to Marsh 1872
- 'Passalacodon littoralis is a subjective synonym of Pantolestes longieundus'
- 'Patriofelis coloradensis belongs to Patriofelis'
- 'Patriofelis leidyanus is recombined as Aelurotherium leidyanum' according to Matthew 1899
- 'Patriofelis leidyanus is recombined as Aelurotherium leidyanum' according to Adams 1896
- 'Patriofelis leidyanus belongs to Patriofelis' according to Osborn and Wortman 1892
- 'Patriofelis leidyanus is a subjective synonym of Patriofelis ferox'
- 'Patriofelis leidyanus is a subjective synonym of Aelurotherium latidens' according to Wortman 1901
- 'Phenacops belongs to '
- 'Phenacops incerta belongs to Phenacops'
- 'Plesiarctomys buccatus is recombined as Sciuravus buccatus'
- 'Pliauchenia vera belongs to Pliauchenia'
- 'Pliohippus pernix is recombined as Protohippus pernix'
- 'Pliohippus robustus is recombined as Protohippus robustus'
- 'Poebrotherium sternbergii is recombined as Paratylopus sternbergi'
- 'Prodaphaenus scotti is recombined as Uintacyon scotti'
- 'Proscalops secundus belongs to Proscalops'
- 'Protohippus lenticularis is recombined as Neohipparion lenticularis'
- 'Protohippus profectus belongs to Protohippus'
- 'Protohippus sejunctus is recombined as Merychippus sejunctus'
- 'Protohippus supremus belongs to Protohippus'
- 'Protolabis longiceps belongs to Protolabis'
- 'Protopsalis is a subjective synonym of Patriofelis'
- 'Protopsalis is a subjective synonym of Patriofelis' according to Osborn 1900
- 'Protopsalis is a subjective synonym of Patriofelis' according to Matthew 1899
- 'Protopsalis tigrinus is recombined as Patriofelis tigrinus'
- 'Protorohippus is a subjective synonym of Eohippus'
- 'Prototomus is a subjective synonym of Sinopa'
- 'Prototomus is a subjective synonym of Sinopa' according to Scott 1892
- 'Prototomus is a subjective synonym of Stypolophus' according to Cope 1877
- 'Prototomus belongs to Hyaenodontidae' according to Cope 1874
- 'Prototomus multicuspis is recombined as Sinopa multicuspis'
- 'Prototomus multicuspis is recombined as Sinopa multicuspis' according to Matthew 1901
- 'Prototomus multicuspis is recombined as Sinopa multicuspis' according to Matthew 1899
- 'Prototomus multicuspis is recombined as Stypolophus multicuspis' according to Cope 1877
- 'Prototomus secundarius is recombined as Sinopa secundaria'
- 'Prototomus secundarius is recombined as Stypolophus secundarius' according to Cope 1877
- 'Prototomus viverrinus is recombined as Sinopa viverrina'
- 'Prototomus viverrinus is recombined as Sinopa viverrina' according to Matthew 1901
- 'Prototomus viverrinus is recombined as Stypolophus viverrinus' according to Cope 1877
- 'Prototomus viverrinus belongs to Prototomus' according to Cope 1874
- 'Sciurus (Prosciurus) vetustus belongs to Sciurus (Prosciurus)'
- 'Sciurus jeffersoni is recombined as Prosciurus jeffersoni'
- 'Steneofiber nebrascensis belongs to Steneofiber'
- 'Stylonus is a subjective synonym of Merychippus'
- 'Stylonus seversus is recombined as Merychippus seversus'
- 'Stypolophus is a subjective synonym of Sinopa'
- 'Stypolophus is a subjective synonym of Sinopa' according to Scott 1892
- 'Stypolophus brevicolcarabus is a subjective synonym of Tritemnodon agilis'
- 'Stypolophus hians belongs to Stypolophus' according to Cope 1877
- 'Stypolophus hians is recombined as Sinopa hians'
- 'Stypolophus hians is recombined as Sinopa hians' according to Matthew 1901
- 'Stypolophus hians is recombined as Sinopa hians' according to Matthew 1899
- 'Stypolophus insectivorus is a nomen dubium'
- 'Stypolophus insectivorus is recombined as Sinopa insectivorus' according to Matthew 1901
- 'Stypolophus pungens is recombined as Sinopa pungens'
- 'Stypolophus pungens is recombined as Sinopa pungens' according to Matthew 1901
- 'Stypolophus pungens is recombined as Sinopa pungens' according to Matthew 1899
- 'Stypolophus whitiae is recombined as Sinopa whitiae'
- 'Stypolophus whitiae is recombined as Sinopa whitiae' according to Matthew 1901
- 'Stypolophus whitiae is recombined as Sinopa whitiae' according to Matthew 1899
- 'Talpavus is a subjective synonym of Nyctitherium'
- 'Talpavus belongs to Erinaceomorpha' according to Marsh 1872
- 'Talpavus nitidus is recombined as Nyctitherium nitidus'
- 'Thinocyon belongs to Limnocyonidae'
- 'Thinocyon belongs to Limnocyonidae' according to Marsh 1872
- 'Thinocyon cledensis belongs to Thinocyon'
- 'Thinocyon minimus belongs to Thinocyon'
- 'Thinocyon mustelinus belongs to Thinocyon'
- 'Thinocyon velox belongs to Thinocyon'
- 'Thinohyus socialis is recombined as Perchoerus socialis'
- 'Tomitherium is a subjective synonym of Notharctus'
- 'Triacodon is a nomen dubium'
- 'Stypolophus aculeatus is a nomen dubium'
- 'Stypolophus aculeatus is a nomen dubium' according to Matthew 1901
- 'Triacodon aculeatus is recombined as Stypolophus aculeatus' according to Cope 1872
- 'Triacodon fallax is a nomen dubium'
- 'Triacodon grandis is a nomen dubium'
- 'Triacodon nanus is a nomen dubium'
- 'Trogolemur belongs to Omomyidae'
- 'Trogolemur myodes belongs to Trogolemur'
- 'Uintacyon (Miocyon) belongs to Uintacyon'
- 'Uintacyon jugulans belongs to Uintacyon'
- 'Uintacyon major belongs to Uintacyon'
- 'Uintacyon promicrodon is recombined as Vassacyon promicrodon'
- 'Uintacyon promicrodon is recombined as Prodaphaenus promicrodon' according to Wortman 1901
- 'Uintacyon pugnax is recombined as Oodectes pugnax'
- 'Uintasorex belongs to Microsyopidae'
- 'Uintasorex parvulus belongs to Uintasorex'
- 'Vassacyon belongs to Miacidae'
- 'Viverravus nitidus is a nomen dubium'
- 'Viverravus sicarius belongs to Viverravus'
- 'Vulpavus (Phlaodectes) belongs to Vulpavus'
- 'Vulpavus (Phlaodectes) ovatus belongs to Vulpavus (Phlaodectes)'
- 'Vulpavus completus belongs to Vulpavus'
- 'Vulpavus hargeri is recombined as Miacis hargeri'
- 'Vulpavus ovatus belongs to Vulpavus'
- 'Vulpavus profectus belongs to Vulpavus'
- 'Ziphacodon is a nomen dubium'
- 'Ziphacodon belongs to ' according to Marsh 1872
- 'Ziphacodon rugatus is a nomen dubium'