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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 p. 611
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()
Bilateria
EubilateriaAx 1987
Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda
Reptiliomorpha
Anthracosauria
subclassAmphibiosauriaKuhn 1967
Cotylosauria()
Amniota
subclassSynapsida
Therapsida()
infraorderCynodontia()
Mammaliamorpha
Mammaliaformes
RankNameAuthor
classMammalia
Theriamorpha(Rowe 1993)
Theriiformes()
Trechnotheria
Cladotheria
Zatheria
subclassTribosphenida()
subclassTheria
Eutheria()
Placentalia
Boreoeutheria
Laurasiatheria
Scrotifera
Euungulata
Panperissodactyla
superorderPerissodactylamorpha
orderPerissodactyla()
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.

Orohippus major Marsh 1874
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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."