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Merychippus sejunctus

Mammalia - Perissodactyla - Equidae

Taxonomy
Protohippus sejunctus was named by Cope (1874) [also attributed to Cope 1884]. Its type specimen is AMNH 8291, a partial skeleton (Complete skull and lower jaws with entire dentition and parts of the skeleton associated, including the hind feet), and it is a 3D body fossil.

It was recombined as Merychippus (Protohippus) sejunctus by Stirton (1940); it was recombined as Pliohippus sejunctus by Quinn (1987); it was recombined as Stylonus sejunctus by Kelly and Lander (1988); it was recombined as Merychippus sejunctus by Hay (1902), Osborn (1904), Trouessart (1905), Gidley (1907), Matthew (1909), Cope and Matthew (1915), Osborn (1918), Matthew (1924), Hay (1930), Stirton (1933), Kelly (1995), MacFadden (1998) and Bravo-Cuevas and Ferrusquía-Villafranca (2006).

Synonymy list
YearName and author
1874Protohippus sejunctus Cope p. 15
1893Protohippus sejunctus Cope p. 25
1902Merychippus sejunctus Hay
1904Merychippus sejunctus Osborn
1905Merychippus sejunctus Trouessart
1907Merychippus sejunctus Gidley p. 891
1909Merychippus sejunctus Matthew
1915Merychippus sejunctus Cope and Matthew pp. Plate CL
1918Merychippus sejunctus Osborn p. 110 figs. Plates 11.1, 16.1,2,3, 19.1,2, 20,4&3, 48.1, 50.1,5, 53.3. Text Figs. 85, 85a, 86
1924Merychippus sejunctus Matthew
1930Merychippus sejunctus Hay
1933Merychippus sejunctus Stirton
1940Merychippus (Protohippus) sejunctus Stirton p. 182
1987Pliohippus sejunctus Quinn
1988Stylonus sejunctus Kelly and Lander
1995Merychippus sejunctus Kelly p. 26
1998Merychippus sejunctus MacFadden p. 547
2006Merychippus sejunctus Bravo-Cuevas and Ferrusquía-Villafranca p. 780

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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
genusMerychippus
speciessejunctus()

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) (1) Size medium, pLm3 .123 (see Gidley); (2) protocone rather large, flattened oval,
united half way down; (3) fossette borders simple, fossette areas contracted; (4) pli caballin rudimentary or absent; (5) metastylid not separate in P2; (6) metastylid and metaconid pillars forming a rather narrow, double column; (7) heel of m3 broad, with internal fold. (8) Lachrymo-malar fossre broad, sessile, sub-united; (9) preorbital region rather short. (10) Ulnar shaft slender, united with radius except near proximal extremity; (11) metapodials and limb bones of moderate length and slenderness; (12) unguals rather narrow.