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Orohippus major

Mammalia - Perissodactyla - Equidae

Taxonomy
Orohippus major was named by Marsh (1874). Its type specimen is YPM 11270, a maxilla (fragment of right maxilla with M2 and M3, and loose M2), and it is a 3D body fossil. Its type locality is Millersville, which is in a Bridgerian terrestrial horizon in the Bridger Formation of Wyoming.

It was recombined as Pliolophus major by Osborn (1890); it was recombined as Hyracotherium major by Stucky (1984).

Synonymy list
YearName and author
1874Orohippus major Marsh p. 248
1875Orohippus major Cope p. 21
1890Pliolophus major Osborn
1898Orohippus major Trouessart
1899Orohippus major Matthew
1902Orohippus major Hay
1908Orohippus major Granger
1930Orohippus major Hay
1940Orohippus major Stirton
1957Orohippus major Kitts p. 7
1984Hyracotherium major Stucky
1998Orohippus major MacFadden p. 543
2002Orohippus major Froehlich p. 151

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Nephrozoa
Deuterostomia
phylumChordataHaeckel 1847
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
Sarcopterygii
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda()
Reptiliomorpha
Anthracosauria
Batrachosauria()
Cotylosauria()
Amniota
Synapsida()
Therapsida()
RankNameAuthor
infraorderCynodontia()
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
subclassTribosphenida()
infraclassEutheria()
Placentalia
orderPerissodactyla()
suborderLophodontomorpha
infraorderEuperissodactyla
Hippomorpha
superfamilyEquoidea
familyEquidae
genusOrohippus
speciesmajor

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Diagnosis
ReferenceDiagnosis
D. B. Kitts 1957Length of M2, 9.3 mm. Mean length of M3, 12.90 mm. (two specimens).Mesostyle weak. Heel of M3 broad and relatively long. In the original description O. major was distinguished from other species of the genus on the basis of its large size and because, in the words of Marsh, "the intermediate lobes of the molars are les well developed and the antero-posterior buttress is more elevated."