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Orohippus pumilus

Mammalia - Perissodactyla - Equidae

Taxonomy
Lophiodon pumilus was named by Marsh (1871) [genotype; not the same as "Lophiodon pumilus"; also said to be 1871, confusing this with Lophiodon pumilus]. It is a 3D body fossil. Its type locality is Grizzly Buttes, which is in a Bridgerian terrestrial horizon in the Bridger Formation of Wyoming. It is the type species of Orohippus, Helohippus.

It was recombined as Hyrachyus pumilus by Leidy (1872); it was synonymized subjectively with Orohippus procyoninus by Cope (1873) and Cope (1875); it was recombined as Helohippus pumilus by Marsh (1892), Matthew (1899) and Hay (1902); it was recombined as Pachynolophus pumilus by Roger (1896); it was recombined as Helaletes pumilus by Wood (1934); it was recombined as Orohippus pumilus by Scott et al. (1871), Marsh (1872), Marsh (1874), Matthew (1899), Hay (1902), Granger (1908), Stirton (1940), Kitts (1957), Gazin (1976), MacFadden (1998) and Froehlich (2002).

Synonyms
  • Helotherium procyoninum was named by Cope (1871) [genotype].

    It was recombined as Orohippus procyoninus by Cope (1875), Hay (1902) and Matthew (1909); it was recombined as Hyracotherium procyoninum by Cope (1877) and Matthew (1899); it was recombined as Lambdotherium procyoninum by Cope (1884) and Roger (1896); it was synonymized subjectively with Orohippus pumilus by Marsh (1874), Trouessart (1905), Granger (1908), Osborn (1929) and Kitts (1957).
  • Hyracotherium osbornianum was named by Cope (1883). It is a 3D body fossil. Its type locality is Black's Fork, which is in a Bridgerian terrestrial horizon in the Bridger Formation of Wyoming.

    It was recombined as Orohippus osbornianus by Trouessart (1898), Hay (1902), Hay (1930) and Stirton (1940); it was synonymized subjectively with Orohippus pumilus by Kitts (1957).
  • Lophiotherium ballardi was named by Marsh (1871) [genotype].

    It was recombined as Orotherium ballardi by Marsh (1872); it was recombined as Pachynolophus ballardi by Roger (1896); it was synonymized subjectively with Orohippus sylvaticus by Matthew (1899); it was recombined as Orohippus ballardi by Hay (1902), Granger (1908), Hay (1930) and Stirton (1940); it was synonymized subjectively with Orohippus pumilus by Kitts (1957).
  • Oligotomus cinctus was named by Cope (1873) [genotype].

    It was recombined as Pliolophus cinctus by Cope (1884); it was recombined as Pachynolophus cinctus by Roger (1896); it was recombined as Orohippus cinctus by Wortman (1896), Matthew (1899), Hay (1902) and Hay (1930); it was synonymized subjectively with Orohippus ballardi by Granger (1908); it was synonymized subjectively with Orohippus pumilus by Kitts (1957).
  • Orohippus atavus was named by Granger (1908). Its type locality is Cottonwood Creek (Lower Bridger), which is in a Bridgerian terrestrial horizon in the Bridger Formation of Wyoming.

    It was synonymized subjectively with Orohippus pumilus by Kitts (1957).
  • Orohippus typicus was named by Granger (1908) ["replacement" for Helohippus pumilus].

    It was synonymized subjectively with Orohippus pumilus by Lull (1913) and Kitts (1957).
Synonymy list
YearName and author
1871Helotherium procyoninum Cope p. 466
1871Lophiodon pumilus Marsh p. 38
1871Lophiotherium ballardi Marsh p. 39
1871Orohippus pumilus Scott and et al.
1872Hyrachyus pumilus Leidy
1872Orohippus pumilus Marsh
1872Orotherium ballardi Marsh
1873Oligotomus cinctus Cope p. 2
1874Orohippus pumilus Marsh p. 249
1875Orohippus procyoninus Cope p. 22
1877Hyracotherium procyoninum Cope
1883Hyracotherium osbornianum Cope p. 647 figs. Plate XXIV; fig. 23
1884Lambdotherium procyoninum Cope
1884Pliolophus cinctus Cope
1892Helohippus pumilus Marsh p. 353
1896Lambdotherium procyoninum Roger
1896Pachynolophus ballardi Roger
1896Pachynolophus cinctus Roger
1896Pachynolophus pumilus Roger
1896Orohippus cinctus Wortman
1898Orohippus osbornianus Trouessart
1899Helohippus pumilus Matthew
1899Hyracotherium osbornianum Matthew
1899Hyracotherium procyoninum Matthew
1899Orohippus cinctus Matthew
1899Orohippus pumilus Matthew
1902Helohippus pumilus Hay
1902Orohippus ballardi Hay
1902Orohippus cinctus Hay
1902Orohippus osbornianus Hay
1902Orohippus procyoninus Hay
1902Orohippus pumilus Hay
1908Hyracotherium osbornianum Granger
1908Orohippus atavus Granger
1908Orohippus ballardi Granger
1908Orohippus pumilus Granger
1908Orohippus typicus Granger
1909Orohippus procyoninus Matthew
1930Orohippus ballardi Hay
1930Orohippus cinctus Hay
1930Orohippus osbornianus Hay
1930Orohippus typicus Hay
1934Helaletes pumilus Wood
1940Orohippus ballardi Stirton
1940Orohippus osbornianus Stirton
1940Orohippus pumilus Stirton
1940Orohippus typicus Stirton
1957Orohippus pumilus Kitts p. 10
1976Orohippus pumilus Gazin
1998Orohippus pumilus MacFadden p. 542
2002Orohippus pumilus Froehlich p. 151

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Nephrozoa
Deuterostomia
phylumChordataHaeckel 1847
OlfactoresJefferies 1991
subphylumVertebrata
Gnathostomata()
Osteichthyes()
Sarcopterygii
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda()
Reptiliomorpha
Anthracosauria
Batrachosauria()
Cotylosauria()
Amniota
Synapsida()
RankNameAuthor
Therapsida()
infraorderCynodontia()
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
subclassTribosphenida()
infraclassEutheria()
Placentalia
orderPerissodactyla()
suborderLophodontomorpha
infraorderEuperissodactyla
Hippomorpha
superfamilyEquoidea
familyEquidae
genusOrohippus
speciespumilus()

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 1957Diastema between pI and p2. P2 with lobe-like posterointernal shelf. P3 with acute (50-55º) antero-external angle and ob- tuse (125-130°) antero-internal angle. Mesostyle very weak or absent on P3 and P4. Anterior and posterior borders of P4 parallel and proto- cone distinctly more medial than hypocone. Mesostyle moderate on molars. P4 may be pointed anteriorly. Heel of M3 narrow and sharply constricted anteriorly.