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Mesohippus bairdi

Mammalia - Perissodactyla - Equidae

Taxonomy
Palaeotherium bairdii was named by Leidy (1850). It is a 3D body fossil.

It was recombined as Anchitherium bairdii by Leidy (1852), Leidy (1853), Leidy (1857), Leidy (1869) and Cope (1873); it was recombined as Mesohippus bairdi by Marsh (1875), King (1878), Osborn (1904), Douglass (1908) and Prothero and Shubin (1989); it was recombined as Miohippus bairdii by Scott (1891), Hay (1902) and Simpson (1985); it was recombined as Kalobatippus bairdii by Joleaud (1919); it was misspelled as Mesohippus bairdii by Stirton (1940) and Scott (1941); it was recombined as Mesohippus bairdii by Osborn and Wortman (1894), Osborn and Wortman (1895), Osborn (1918) and MacFadden (1998).

Synonyms
Synonymy list
YearName and author
1850Palaeotherium bairdii Leidy p. 122
1852Anchitherium bairdii Leidy
1853Anchitherium bairdii Leidy
1857Anchitherium bairdii Leidy p. 89
1869Anchitherium bairdii Leidy
1873Anchitherium bairdii Cope p. 14
1875Mesohippus bairdi Marsh p. 248
1878Mesohippus bairdi King
1891Miohippus bairdii Scott
1894Mesohippus bairdii Osborn and Wortman p. 353
1895Mesohippus bairdii Osborn and Wortman p. 352
1902Miohippus bairdii Hay
1904Mesohippus bairdi Osborn
1904Mesohippus hypostylus Osborn
1904Mesohippus proteulophus Osborn
1904Mesohippus hypostylus Osborn pp. 170-171 figs. 2, pl. V A
1904Mesohippus proteulophus Osborn pp. 171-172 figs. Plates 1.1, 2.2, text Fig. 23 of [Osborn 1918]
1908Mesohippus portentus Douglass p. 268 figs. Pl. LXV, Figures 1-4
1908Mesohippus hypostylus Douglass p. 269
1908Mesohippus bairdi Douglass p. 270
1918Mesohippus portentus Osborn p. 40 figs. Text Fig. 21
1918Mesohippus hypostylus Osborn p. 41 figs. Plates 1.2, 2.3. Text Fig. 22
1918Mesohippus proteulophus Osborn p. 41 figs. Plates 1.1, 2.2. T ext Fig. 23
1918Mesohippus bairdii Osborn p. 45 figs. Plates 1.3,4, 2.4,13, 39.15,18, 51.7,11. Text Figs. 25, 26
1919Kalobatippus bairdii Joleaud
1935Pediohippus portentus Schlaikjer p. 144
1940Mesohippus bairdii Stirton p. 170
1940Mesohippus hypostylus Stirton p. 170
1940Mesohippus protentus Stirton p. 170
1940Mesohippus proteulophus Stirton p. 170
1941Mesohippus bairdii Scott
1941Pediohippus portentus Scott
1951Mesohippus portentus Macdonald
1967Mesohippus viejensis Clark and Beerbower
1970Mesohippus proteulophus Forsten
1985Miohippus bairdii Simpson
1989Mesohippus bairdi Prothero and Shubin
1998Mesohippus bairdii MacFadden p. 543

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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()
RankNameAuthor
infraorderCynodontia()
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
subclassTribosphenida()
infraclassEutheria()
Placentalia
orderPerissodactyla()
suborderLophodontomorpha
infraorderEuperissodactyla
Hippomorpha
superfamilyEquoidea
familyEquidae
subfamilyAnchitheriinae()
genusMesohippus
speciesbairdi()

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 (Mesohippus hypostylus)(Osborn, 1904, p. 170) "Distinguished from the preceding species by (I) a clearly defined but rudimentary hypostyle just budding off from the posterior cingulum, (2) by protoloph tending to unite with paracone [para- style]; from M. bairdi[i] by more rudimentary hypostyle and less elevated crests. Metaloph sharp; metaconule not defined at base. Pm1 small. Skull with preorbital [lachrymal] fossa apparently deeper than in M. bairdi[i]."
H. F. Osborn 1918 (Mesohippus portentus)(Douglass 1908) "(1) Size large and (2) crests of molars high for a horse from this horizon, (3) ectoloph very oblique, (4) protoloph and metaloph nearly equal in length, (5) protoloph large and connected with the parastyle, (6) metaloph narrow and nearly connected with ectoloph, (7) protoconule easily distinguishable, but (8) metaconule absent, (9) a crotchet present on the metaloph, and (10) a small conule in the posterior valley of the tooth, (11) a rudiment of a cingulum between protocone and hypocone, (12) parastyle and (13) hypostyle small."
(Osborn, 1918) The exceptionally progressive characters of these type molar teeth, including the purely lophoid metaloph and the rudimentary crochet, indicate that animal may belong to a higher geologic horizon than the Titanotherium zone.
H. F. Osborn 1918 (Mesohippus proteulophus)(Osborn, 1904) "This is a relatively large animal for the Titanotherium beds, and is the oldest horse known with perfect crests on the molar teeth - hence the name proteulophus. The superior molars are readily distinguished by: (1) their large size; p3-m2 measure .037 mm. as compared with .0335 for the same teeth in M. bairdi[i]; (2) by the primitive absence of a distinct hypostyle; (3) especially by the very advanced or progressive condition of the protoand metalophs which are continued to the ectoloph, and are very little divided, thus resembling those of M. eulophus; (4) the external cingulum sweeps upward across the parastyle instead of rising with it. rna measure 79 mm., indicating an animal of large size."
H. F. Osborn 1918(Leidy, 1851, p. 122) Type. "This species is about two-thirds the size of P. crassum. The arrange-
ment of the superior molars is very like that of Palreotherium Hippoides... .This second species Dr. L. named P. bairdii, in honor of Prof. S. F. Baird, Curator of the Smithsonian Institution."
(Osborn, 1904, 1918) (1) Skull with a distinct lachrymal fossa; (2) cranial (orbito- postorbital) region exceeds facial (preorbital) region in length; (3) molars with crests interrupted and moderately elevated; (4) small hypostyle present as a small bud or crest connected with posterior cingulum; (5) protoloph tending to unite with parastyle, interrupted by protoconule; (6) metaloph relatively sharp and continuous; (7) parastyle teiiding to connect with protoloph; (8) internal cingulum present in medivallum of m3 only.