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Pliohippus mirabilis

Mammalia - Perissodactyla - Equidae

Taxonomy
Merychippus mirabilis was named by Leidy (1858). Its type specimen is USNM 569, a partial skull (A fragment of the right maxillary containing the posterior two milk molars, and the first true molar partially calcified), and it is a 3D body fossil.

It was recombined as Protohippus mirabilis by Cope (1892), Cope (1893), Trouessart (1898), Gidley (1903) and Gidley (1906); it was synonymized subjectively with Merychippus (Protohippus) perditus by Stirton (1940); it was considered a nomen dubium by Macdonald (1992); it was recombined as Pliohippus mirabilis by Matthew (1899), Gidley (1907), Osborn (1918), Matthew (1918), Hay (1930), Matthew and Stirton (1930), Quinn (1955), Hulbert (1989), Voorhies (1990), Kelly (1995), Prado and Alberdi (1996), MacFadden (1998) and Kelly (1998).

Synonyms
Synonymy list
YearName and author
1858Merychippus mirabilis Leidy p. 27
1892Protohippus mirabilis Cope
1893Protohippus mirabilis Cope p. 25
1898Protohippus mirabilis Trouessart
1899Pliohippus mirabilis Matthew
1902Merychippus mirabilis Hay
1903Merychippus mirabilis Gidley
1903Protohippus mirabilis Gidley
1905Merychippus mirabilis Trouessart
1906Protohippus mirabilis Gidley
1907Merychippus campestris Gidley
1907Pliohippus mirabilis Gidley
1907Merychippus campestris Gidley p. 928
1918Pliohippus mirabilis Matthew
1918Merychippus campestris Osborn p. 114 figs. Plates 15.4,5, 19.3,4, 26.1, 44.1, 49.1, 50.3,7. Text Figs. 88, 89.
1918Pliohippus mirabilis Osborn p. 148 figs. Plates 25.10, 26.3. Text Fig. 117
1930Pliohippus mirabilis Hay
1930Pliohippus mirabilis Matthew and Stirton
1940Merychippus (Protohippus) campestris Stirton p. 182
1955Pliohippus mirabilis Quinn p. 22
1989Pliohippus mirabilis Hulbert, Jr.
1990Pliohippus mirabilis Voorhies
1995Pliohippus mirabilis Kelly p. 14
1996Pliohippus mirabilis Prado and Alberdi p. 676
1998Pliohippus mirabilis Kelly
1998Pliohippus mirabilis MacFadden p. 550

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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()
infraorderCynodontia()
RankNameAuthor
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
subclassTribosphenida()
infraclassEutheria()
Placentalia
orderPerissodactyla()
suborderLophodontomorpha
infraorderEuperissodactyla
Hippomorpha
superfamilyEquoidea
familyEquidae
subfamilyEquinaeSteinmann and Döderlein 1890
tribeEquini
genusPliohippus
speciesmirabilis()

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
H. F. Osborn 1918 (Merychippus campestris)(Gidley, 1907, pp. 928, 929) (1) Superior molars of the same general appearance as those of Pliohippus
spectans Cope, but differing in the following characters: (2) the molars with shorter crowns; (3) external cones (pa, ma) thicker transversely, making less transverse width for the fossettes; (4) protocone smaller and more rounded, being nearly circular in outline; (5) as in P. spectans the horns of the fossettes end in broadly open loops; (6) the enamel borders are very simple throughout. (7) Lower jaws comparatively long and slender. (8) Mtc. III moderately short and heavy, lateral metacarpals very much reduced. (Osborn, 1918) (9) Enamel plications very simple; (10) protocone extended inward more than hypocone, suggesting some of the simple Pliohippus types of molar.
H. F. Osborn 1918 (Leidy, 1858) (1) " ...a deep depression or lachrymal fossa in advance of the orbit, as in the deer,
Oreodon, etc." (Leidy, 1869, p. 294, Osborn, 1918) (2) Deciduous premolars provided with cement; (3) enamel fold- ings around the fossettes as simple as in the horse; (4) protocones conoid, continuous with protoconule; (5) protocone and hypocone on the same longitudinal plane and of equal size; (6) a pli caballin and single enamel fold entering the -pre- and postfossettes from metaloph in m1; (7) enamel of dp3- 4 more ptychoid. Leidy's fuller description of his Pliohippus (Merychippus) mirabilis type is contained in his discussion of the genus Merychippus (1869, pp. 292-296).