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Pliohippus pernix

Mammalia - Perissodactyla - Equidae

Taxonomy
Pliohippus pernix was named by Marsh (1874) [genotype]. Its type specimen is YPM 13007, a partial skeleton (portions of a skull, jaws, the right pes, part of the left tibire, and so on. Also the left manus, radius, ulna and humerus, and several vertebrre. The left sup), and it is a 3D body fossil. It is the type species of Pliohippus.

It was recombined as Hippidium pernix by Cope (1880); it was recombined as Protohippus pernix by Gidley (1903) and Matthew (1909); it was recombined as Pliohippus (Pliohippus) pernix by Stirton (1940); it was considered a nomen dubium by Macdonald (1992).

Synonyms
Synonymy list
YearName and author
1874Pliohippus pernix Marsh p. 252
1874Pliohippus robustus Marsh p. 253
1880Hippidium pernix Cope
1880Hippidium robustus Cope
1896Pliohippus pernix Roger
1896Pliohippus robustus Roger
1897Pliohippus pernix Marsh
1898Pliohippus pernix Trouessart
1898Pliohippus robustus Trouessart
1899Pliohippus pernix Matthew
1899Pliohippus robustus Matthew
1902Pliohippus pernix Hay
1902Pliohippus robustus Hay
1903Protohippus pernix Gidley
1905Pliohippus pernix Trouessart
1907Pliohippus pernix Gidley p. 892
1907Pliohippus robustus Gidley p. 894
1909Protohippus pernix Matthew
1909Protohippus robustus Matthew
1916Pliohippus lullianus Troxell
1918Pliohippus pernix Osborn p. 151 figs. Plates 25.12, 28.1. Text Figs. 120, 121, 122
1918Pliohippus robustus Osborn p. 155 figs. Text Fig. 123
1918Pliohippus lullianus Osborn p. 160 figs. Plate 27. Text Fig. 127
1924Pliohippus pernix Matthew
1930Pliohippus robustus Hay
1930Pliohippus pernix Matthew and Stirton
1930Pliohippus robustus Matthew and Stirton
1940Pliohippus (Pliohippus) lullianus Stirton p. 192
1940Pliohippus (Pliohippus) pernix Stirton p. 192
1940Pliohippus (Pliohippus) robustus Stirton p. 192
1942Pliohippus pernix Henshaw
1955Pliohippus pernix Quinn p. 22
1969Pliohippus pernix Webb
1987Pliohippus lullianus Quinn
1988Pliohippus lullianus Kelly and Lander
1989Pliohippus pernix Hulbert, Jr.
1990Pliohippus pernix Voorhies
1995Pliohippus pernix Kelly p. 14
1998Pliohippus pernix Kelly
1998Pliohippus pernix 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
speciespernix

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 (Pliohippus lullianus) (Troxell, pp. 341-343) "Metacarpals.- The especial character which distinguishes this specimen is
its monodactyly. It has commonly been predicted that one-toed specimens of the Protohippinre would be found, but no positive evidence of this feature has, heretofore, been presented. The splints, Metacarpals II and IV, unlike those of Equua, extend the lengths of the cannon bone, but like those of the modem horse they bear no digits on the ends. These slender bones are large proximally, but at once decreasing in size they run at a uniform diameter to the middle; in the next fourth of the distance they decrease to a width of about 3 mm. and a thickness of less than 1.5 mm. The distal ends are enlarged to receive the pointed epiphyses, the larger one of which measures 6 mm. in length. They show no evidence of articular facets; in fact their very sharp ends eliminate the possibility of their ever having borne phalanges."
H. F. Osborn 1918 (Marsh, 1874, p. 252) (1) Differs from Protohippus in the absence of lateral digits, which are only represented by slender splint bones; (2) presence of large antorbital [lachrymal] fossa; (3) presence of functional first upper premolar. (4) First lower premolar wanting; (5) molars with short crowns and distinct fangs; (6) enamel folds of the molar teeth very simple; (7) skull comparatively short; (8) ulna shaft incomplete at centre; (9) distal end of ulnaand fibula coalesced with radius and tibia respectively; (10) small trapezium; (11) a rudiment of the fifth metacarpal attached to the unciform; (12) limbs more elongate than in Equus asinus; (13) size about that of Equus asinus; (14) ungual pha- langes broader and slightly cleft their extremities; (15) relatively large cubo-astragalar facet. (Gidley, 1907, p. 893) (1,6) The type an old individual with teeth so much worn as to obliterate distinctive characters. (17) Lateral meta- podials broken. (18) As compared with Equus the preorbital region is short; (19) angle of the jaw of great depth, and molars proportionately short-crowned and curved; (20) characteristic facial pits, or fossre, including (?) a deep lachrymal pit.
H. F. Osborn 1918 (Pliohippus robustus)(Marsh, 1874, p. 253) (1) Of nearly the same size as the type of Pliohippua pernix, but limbs shorter and
stouter; (2) the first upper premolar much larger, the upper molars longer and much curved; (3) enamel foldings more complex than in P. pernix. (Gidley, 1907, p. 894) (4) Aside from the difference in the proportions of the bones, the charactersassigned byMarsh are indicative of age differences only, the type of P. robustua being ayoungadult, that of P. pemix an aged individual; (5) the comparative measurements of limb and foot bones indicate that P. robuatua is a shorter animal and of more robust proportions; (6) terminal phalanx well rounded, with the posteroexternal processes much reduced as in the modern horse, but the plane of the proximal articular facet directed more backward as in the other species of Miocene horses. (7) This species is not clearly distinguished from P. supremus Leidy, with which it agrees in size and general characters so far as they are known.