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Protohippus perditus

Mammalia - Perissodactyla - Equidae

Taxonomy
Equus (Protohippus) perditus was named by Leidy (1858) [subgenus Protohippus]. Its type specimen is USNM 619, a partial skull (a fragment of an upper jaw containing the posterior four molars, P4-M3), and it is a 3D body fossil. Its type locality is Niobrara River (coll. Hayden 1857), which is in a Miocene terrestrial horizon in the Loop Fork Formation of Nebraska. It is the type species of Protohippus, Equus (Protohippus).

It was recombined as Merychippus perditus by Hay (1902), Trouessart (1905), Stirton (1933), McGrew and Meade (1938), Henshaw (1942), Hesse (1943) and Forsten (1975); it was recombined as Merychippus (Protohippus) perditus by Stirton (1940); it was recombined as Protohippus perditus by Leidy (1869), King (1878), Cope (1889), Cope (1893), Trouessart (1898), Matthew (1899), Gidley (1906), Gidley (1907), Matthew (1909), Cope and Matthew (1915), Osborn (1918), Matthew (1918), Matthew (1924), Matthew and Stirton (1930), Quinn (1955), Evander (1978), Hulbert (1988), Prado and Alberdi (1996) and MacFadden (1998).

Synonyms
  • Eoequus wilsoni was named by Quinn (1955) [genotype; type locality is 18628]. Its type specimen is BEG 31183-30, -37, and -66, a skull (skull and mandible with disassociated p2), and it is a 3D body fossil.

    It was synonymized subjectively with Merychippus circulus by Forsten (1975); it was synonymized subjectively with Protohippus perditus by Hulbert (1988) and MacFadden (1998).
  • Protohippus profectus was named by Cope (1889) [apparently also using "Hippotherium profectus" in the same paper]. Its type specimen is AMNH 8349, a set of teeth (Six superior molars), and it is a 3D body fossil.

    It was synonymized subjectively with Merychippus perditus by Hay (1902); it was recombined as Pliohippus profectus by McGrew and Meade (1938); it was recombined as Merychippus (Protohippus) profectus by Stirton (1940); it was synonymized subjectively with Protohippus perditus by Cope (1893), Hulbert (1988) and MacFadden (1998).
Synonymy list
YearName and author
1858Equus (Protohippus) perditus Leidy p. 26
1869Protohippus perditus Leidy
1878Protohippus perditus King
1889Protohippus perditus Cope
1889Protohippus profectus Cope
1893Protohippus perditus Cope p. 24
1898Protohippus perditus Trouessart
1899Protohippus perditus Matthew
1902Merychippus perditus Hay
1905Merychippus perditus Trouessart
1906Protohippus perditus Gidley
1907Protohippus perditus Gidley
1907Protohippus profectus Gidley p. 907
1909Protohippus perditus Matthew
1909Protohippus profectus Matthew
1915Protohippus perditus Cope and Matthew
1918Protohippus perditus Matthew
1918Protohippus perditus Osborn p. 129 figs. Plates 21.3, 25.8. Text Figs. 102, 103, 116a
1918Protohippus profectus Osborn p. 143 figs. Plate 22.3. Text Fig. 115
1924Protohippus perditus Matthew
1930Protohippus perditus Matthew and Stirton
1933Merychippus perditus Stirton
1938Merychippus perditus McGrew and Meade p. 201
1938Pliohippus profectus McGrew and Meade p. 201
1940Merychippus (Protohippus) perditus Stirton p. 182
1940Merychippus (Protohippus) profectus Stirton p. 182
1942Merychippus perditus Henshaw
1943Merychippus perditus Hesse
1955Protohippus perditus Quinn p. 17
1955Eoequus wilsoni Quinn p. 54 figs. Pls. 10 - 13
1975Merychippus perditus Forsten
1978Protohippus perditus Evander
1988Protohippus perditus Hulbert, Jr. p. 282 fig. 22A
1996Protohippus perditus Prado and Alberdi p. 676
1998Protohippus perditus MacFadden p. 550

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Nephrozoa
Deuterostomia
phylumChordataHaeckel 1847
OlfactoresJefferies 1991
subphylumVertebrata
Gnathostomata()
Osteichthyes()
Sarcopterygii
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda()
Reptiliomorpha
Anthracosauria
Batrachosauria()
Cotylosauria()
Amniota
Synapsida()
Therapsida()
RankNameAuthor
infraorderCynodontia()
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
subclassTribosphenida()
infraclassEutheria()
Placentalia
orderPerissodactyla()
suborderLophodontomorpha
infraorderEuperissodactyla
Hippomorpha
superfamilyEquoidea
familyEquidae
subfamilyEquinaeSteinmann and Döderlein 1890
tribeEquini
genusProtohippus()
speciesperditus()

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(Leidy, 1858) (1) The portion of jaw is like the corresponding part in the recent horse. (2) Molar
teeth with their crowns about one-half worn; (3) enamel folds even less complex than in the recent horse; (4) antero- internal fold [protocone] of the same form, direction, and mode of continuation as the posterointernal fold [hypocone]. (Gidley, 1907) (5) Moderately small size. (6) Laterally compressed and backwardly directed protocone and hypocone of the upper molars. (7) Shallow, not sharply defined lachrymal fossa; (8) rudimentary condition or entire absence of malar fossa.
H. F. Osborn 1918 (Protohippus profectus) (Cope, 1889, Osborn, 1918) (1) In dimensions the type of this species is about equal to" Hippotherium" apecioaum [a referred specimen]; (2) "The other six (with one exception) are less worn, and present a less complex folding of the enamel plates [than in Protohippus retruaua]"; (3) protocone of the same flattened form as in P. retrusua but con- nected with protoconule by a narrow isthmus; (4) separated in two of the teeth from the metaconule; (5) p2 presenting a complete fusion; (6) approaching nearer to Equua than any known species of Equua or Hippidium.
J. H. Quinn 1955 (Eoequus wilsoni)ize large; teeth robust and heavily cemented, high crowned, mod- erately curved; styles pronounced, valleys deep, ribs reduced; fossettes large with pli protoloph and pli hypoloph; proto- cones elongate, heeled anteriorly, grooved lingually, oriented with Ion" axis of tooth row, disconnected at ~ummi; of crowns but with long spurs connecting as narrow com- missures about 10 mm below unworn sum- mit of crowns; lower teeth with unequal metaconids and metastylids; protoconids and hypoconids slightly flattened; in- cipient pli caballinids on all teeth; para- stylids on all teeth.
J. H. Quinn 1955per teeth strongly hyp- sodont, little curved; ectoloph flattened, styles more prominent than in later species; fossettes large and simple but less so than in later species; protocones small
and oval; no pli caballin on the molars; lower teeth with the parastylid nearly eliminated but oriented as in Hippodon; metaconid and metastylid small and of nearly equal size with the metastylid sharply restricted; flexids plicate at early
state of wear.
R. C. Hulbert 1988Slightly smaller and less hypsodont than P. supremus, with toothrow lengths of about 120 to 135 mm and unworn molar crown heights of about 47 mm. Relatively short postcanine diastema and large DPl. Shorter, more oval protocones than P. supremus or P. gidleyi; also shorter metaconid-metastylid complexes and entoflexid lengths.