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Pseudhipparion retrusum

Mammalia - Perissodactyla - Equidae

Taxonomy
Hippotherium retrusum was named by Cope (1889). Its type specimen is AMNH 8350, a set of teeth (two upper molars), and it is a 3D body fossil.

It was recombined as Hipparion retrusum by Trouessart (1898) and Hay (1902); it was recombined as Neohipparion retrusum by Matthew (1909) and Merriam (1917); it was recombined as Protohippus retrusus by Osborn (1918) and Hay (1930); it was recombined as Nannippus retrusus by McGrew and Meade (1938), Stirton (1940) and Lance (1950); it was recombined as Griphippus retrusus by Quinn (1955); it was considered a nomen dubium by Macdonald (1992); it was recombined as Pseudhipparion retrusum by Ameghino (1904), Webb (1969), Webb and Hulbert (1986), Kelly and Lander (1988) and MacFadden (1998).

Synonymy list
YearName and author
1889Hippotherium retrusum Cope p. 446
1898Hipparion retrusum Trouessart
1902Hipparion retrusum Hay
1904Pseudhipparion retrusum Ameghino
1907Hippotherium retrusum Gidley p. 906
1909Neohipparion retrusum Matthew
1917Neohipparion retrusum Merriam
1918Protohippus retrusus Osborn p. 142 figs. Text Fig. 114
1930Protohippus retrusus Hay
1938Nannippus retrusus McGrew and Meade p. 201
1940Nannippus retrusus Stirton p. 186
1950Nannippus retrusus Lance
1955Griphippus retrusus Quinn
1969Pseudhipparion retrusum Webb
1986Pseudhipparion retrusum Webb and Hulbert, Jr.
1988Pseudhipparion retrusum Kelly and Lander
1998Pseudhipparion retrusum MacFadden p. 548

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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
tribeHipparionini
genusPseudhipparionAmeghino 1904
speciesretrusum()

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 (Matthew, 1913, Osborn, 1918) (1) Molar size intermediate, somewhat larger than in P. placidus but
apparently with shorter crowns; (2) crowns strongly curved; (3) protocone separate from protoloph in m2, united in m1; (4) protocone and hypocone united by longitudinal isthmus; (5) protocone flattened oval, posterior in position; (6) pli caballin fold present on little worn teeth, absent on half worn teeth; (7) two folds and minor accessory folds on each side of metaloph projecting into pre- and postfossettes; (8) a single inferior fold (crochet) in prefossette; (9) parastyle narrow, mesostyle broad at base and narrowing rather slightly toward crown.
(Matthew, 1913) "These two type teeth cannot go together as placed; they may not belong to the same animal; the right hand tooth (A) might be Merychippus; the left hand tooth, if normal, does not agree well with any of the genera. If normal it represents an undescribed genus on the criteria used to separate the Miocene and Pliocene genera. If placed in Protohippus it should be in quotes."