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Mesohippus westoni

Mammalia - Perissodactyla - Equidae

Taxonomy
Anchitherium westoni was named by Cope (1889). Its type specimen is Ottawa Mus. 6289, a set of teeth (a single superior molar, and two inferior molars, the latter in place in a part of the mandible.), and it is a 3D body fossil.

It was recombined as Miohippus westonii by Hay (1902); it was considered a nomen dubium by Macdonald (1992); it was recombined as Mesohippus westoni by Roger (1896), Matthew (1899), Osborn (1904), Lambe (1905), Lambe (1908), Osborn (1918), Hay (1930), Stirton (1940), Scott (1941), Russell (1975), Prothero and Shubin (1989), Storer and Bryant (1993) and MacFadden (1998).

Synonyms
Synonymy list
YearName and author
1889Anchitherium westoni Cope p. 153
1891Anchitherium westonii Cope p. 20
1896Mesohippus westoni Roger
1899Mesohippus westoni Matthew
1902Miohippus westonii Hay p. 614
1904Mesohippus montanensis Osborn
1904Mesohippus westoni Osborn p. 168
1905Mesohippus westoni Lambe
1905Mesohippus praecocidens Lambe p. 46
1908Mesohippus praecocidens Lambe
1908Mesohippus westoni Lambe
1918Mesohippus westoni Osborn p. 38 figs. Plate 2.10. Text Fig. 18
1918Mesohippus montanensis Osborn p. 39 figs. Plate 2.1. Text Fig. 20
1918Mesohippus praecocidens Osborn p. 42 figs. Text Fig. 24(14)
1930Mesohippus westoni Hay
1940Mesohippus montanensis Stirton p. 170
1940Mesohippus praecocidens Stirton p. 170
1940Mesohippus westoni Stirton p. 170
1941Mesohippus westoni Scott
1975Mesohippus westoni Russell
1989Mesohippus westoni Prothero and Shubin
1993Mesohippus westoni Storer and Bryant
1998Mesohippus westoni MacFadden p. 543
2001Mesohippus montanensis Tabrum et al.

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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
RankNameAuthor
—Mammaliaformes
classMammalia
—Cladotheria
—Zatheria
subclassTribosphenida()
subclassTheria
—Eutheria()
—Placentalia
—Boreoeutheria
—Laurasiatheria
—Scrotifera
—Euungulata
—Panperissodactyla
superorderPerissodactylamorpha
orderPerissodactyla()
superfamilyEquoidea
familyEquidae
subfamilyAnchitheriinae()
genusMesohippus
specieswestoni()

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.

†Mesohippus westoni Cope 1889
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Invalid names: Mesohippus montanensis Osborn 1904 [synonym], Mesohippus praecocidens Lambe 1905 [synonym]
Diagnosis
ReferenceDiagnosis
H. F. Osborn 1918Superior ex:tremely primitive and brachyodont; transverse diameter propor-
tionately great; crests low and obtuse; persistent, well defined internal cingulum; protoloph with defined protoconule; met!J.loph continuous, with metaconule somewhat less clearly defined; no hypostyle.
H. F. Osborn 1918 (Mesohippus montanensis) (Osborn, 1904, p. 170)"Distinguished from M. celer by full size of m3 ; from M. westoni by sharp elevation of crests and absence of internal cingulum; from M. latidens by smaller parastyle and sub-equal length of protoloph and metaloph. Molars more quadrate in form than in M. latidens. Protoconule quite distinct in protoloph; metaconule well defined on base of metaloph. Hypostyle absent or extremely rudimentary. A fore foot associated with a single m3 of the same species exhibits a large splint of Mtc. v."
H. F. Osborn 1918 (Mesohippus praecocidens)(Lambe, 1905) "This tooth is about the size of, or possibly smaller than, M. westoni, but is more progressive in every way. There is an entire absence of an internal cingulum, the cross crests are better developed and rela- tively higher with steeper slopes. The protoconule is relatively larger, and the metaconule, although defined, scarcely breaks the continuity of the metaloph which unites in a decided manner with the ectoloph. The protoconule is distinctly • defined in the protoloph and connects closely with the forward slope of the paracone. The hypocone has about the same height as the protocone. The anterior cingulum is strong."
Measurements
No measurements are available
Composition: phosphaticsubp
Environment: terrestrialsubc
Locomotion: actively mobilec
Life habit: ground dwellingf
Diet: browserf
Reproduction: viviparoussubc
Created: 2005-06-08 10:11:09
Modified: 2005-08-31 16:55:50
Source: f = family, subc = subclass, c = class, subp = subphylum
References: Nowak 1991, Carroll 1988, Ji et al. 2002, Lillegraven 1979, Hendy et al. 2009

Age range: Chadronian or 37.20000 to 33.90000 Ma

Collections (10 total)


Time interval Ma Country or state Original ID and collection number
Chadronian37.2 - 33.9USA (North Dakota) Mesohippus westoni (16991)
Chadronian37.2 - 33.9Canada (Saskatchewan) Anchitherium westonii (101961) Mesohippus sp. (17023) Mesohippus westoni (16893 16919)
Chadronian37.2 - 33.9USA (Wyoming) Mesohippus montanensis (16920) Mesohippus westoni (17011)
Chadronian37.2 - 33.9USA (Montana) Mesohippus montanensis (17010) Mesohippus westoni (16988)
Middle Chadronian37.2 - 33.9Canada (Saskatchewan) Mesohippus westoni (16928)