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Merychippus missouriensis

Mammalia - Perissodactyla - Equidae

Taxonomy
Merychippus missouriensis was named by Douglass (1908). Its type specimen is CM 905, a partial skeleton (a portion of a skull, a mandible, a radius, two femora, two complete and two incomplete metapodials, also numerous fragments), and it is a 3D body fossil. Its type locality is Canyon Ferry Reservoir Earl Douglass Location, which is in a Hemingfordian terrestrial horizon in Montana.

It was recombined as Merychippus (Merychippus) missouriensis by Stirton (1940); it was recombined as Stylonus missouriensis by Kelly and Lander (1988).

Synonymy list
YearName and author
1908Merychippus missouriensis Douglass p. 274 figs. Pl. LXVI; LXVII, Fig. 5; Pl. LXVIII, Figs. 1 and 2
1918Merychippus missouriensis Osborn p. 119 fig. 93
1940Merychippus (Merychippus) missouriensis Stirton p. 181
1988Stylonus missouriensis Kelly and Lander
2001Merychippus missouriensis Tabrum and Nichols p. 92

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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
subfamilyEquinae
genusMerychippus
speciesmissouriensis

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.

Merychippus missouriensis Douglass 1908
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Diagnosis
ReferenceDiagnosis
H. F. Osborn 1918(Douglass, p. 274) (1) Lachrymal fossa long and moderately deep; (2) malar pit with steep posterior side, bounded below by a thin, shelf-like malar-maxillary ridge. (3) Temporary molars brachyodont or brachy-hypsodont; (4) permanent molars curved and strongly hypsodont; (5) both series of teeth with a coating of cement which is not very thick; (6) enamel lakes simple with only one or two simple enamel folds on each; (7) protocone and hypocone laterally
compressed, the former separate from the protoconule but having an angular projection toward the latter; (8) first tempo- rary lower molar minute; (9) intermediate external conule on lower temporary molars concave on the inside, more or less flattened on the outside. (10) Metapodial nearly ninety per cent. of the length of the radius and eighty-four per cent. of the length of the femur exclusive of the proximal epiphysis.
(Matthew, 1913) The deciduous premolars are moderately high-crowned. This general type is difficult to distinguish from M. isonesus Cope, with which it agrees in size.