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Cormohipparion occidentale

Mammalia - Perissodactyla - Equidae

Taxonomy
Hipparion occidentale was named by Leidy (1856) [also said to be 1869 by Skinner et al. 1977]. It is a 3D body fossil.

It was recombined as Hippotherium occidentale by Lydekker (1882), Wortman (1883), Cope (1886), Cope (1889), Cope (1892), Cope (1893) and Gidley (1903); it was recombined as Neohipparion occidentale by Gidley (1904), Trouessart (1905), Gidley (1906), Gidley (1907), Matthew (1909), Merriam (1911), Hesse (1940), Stirton (1940), Gregory (1942), Macdonald (1960), Dalquest and Hughes (1966) and Forsten (1975); it was considered a nomen dubium by Macdonald (1992) and Alroy (2007); it was recombined as Cormohipparion occidentale by MacFadden (1984), Woodburne (1996), Dalquest et al. (1996), MacFadden (1998), Woodburne (2007), Boessenecker (2011) and May (2019).

Synonyms
  • Hipparion mohavense callodonte was named by Merriam (1915) [Type locality is Ricardo (19517)]. Its type specimen is UCMP 21311, a set of teeth (finely preserved dentition including the upper and lower cheek·teeth with several of the incisors), and it is a 3D body fossil.

    It was synonymized subjectively with Cormohipparion occidentale by MacFadden (1984).
  • Hipparion mohavense was named by Merriam (1913). Its type specimen is UCMP 19787, a set of teeth (an upper premolar three with two associated upper cheek-teeth, and several lower teeth presumably from the same individual), and it is a 3D body fossil. Its type locality is Ricardo, which is in a Clarendonian terrestrial horizon in the Dove Spring Formation of California.

    It was considered a nomen dubium by Macdonald (1992); it was synonymized subjectively with Cormohipparion occidentale by MacFadden (1984), Whistler (1991), MacFadden (1998) and Kelly (1998).
  • Hipparion platystyle was named by Merriam (1915). Its type specimen is UCMP 19830, a tooth (a second upper premolar, p2, of the right side, with the walls of the crown partially fractured), and it is a 3D body fossil. Its type locality is UCMP 708, West of Tassajero, which is in a Miocene/Pliocene terrestrial horizon in California.

    It was synonymized subjectively with Cormohipparion occidentale by MacFadden (1984); it was considered a nomen dubium by Macdonald (1992).
Synonymy list
YearName and author
1856Hipparion occidentale Leidy p. 59
1857Hipparion occidentale Leidy p. 89
1882Hippotherium occidentale Lydekker
1883Hippotherium occidentale Wortman
1886Hippotherium occidentale Cope
1889Hippotherium occidentale Cope p. 434
1892Hippotherium occidentale Cope
1893Hippotherium occidentale Cope p. 36
1902Hipparion occidentale Hay p. 620
1903Hippotherium occidentale Gidley
1904Neohipparion occidentale Gidley
1905Neohipparion occidentale Trouessart
1906Neohipparion occidentale Gidley
1907Neohipparion occidentale Gidley p. 877
1909Neohipparion occidentale Matthew
1911Neohipparion occidentale Merriam
1913Hipparion mohavense Merriam p. 436 figs. 1a - 3b
1915Hipparion platystyle Merriam
1915Hipparion mohavense callodonte Merriam p. 52
1918Hipparion occidentale Osborn p. 176 figs. Plates 25.9, 34.5. Text Fig. 140
1918Hipparion platystyle Osborn p. 188 figs. Text Fig. 151
1918Hipparion mohavense Osborn p. 193 figs. Text Fig: 157
1924Hipparion occidentale Matthew
1925Hipparion occidentale Merriam et al.
1928Hipparion occidentale Merriam and Stock
1930Hipparion occidentale Hay
1930Hipparion occidentale Matthew and Stirton
1935Hipparion occidentale Hesse
1940Neohipparion occidentale Hesse
1940Neohipparion occidentale Stirton p. 183
1940Hipparion mohavense Stirton p. 184
1940Hipparion platystyle Stirton p. 184
1942Neohipparion occidentale Gregory
1960Neohipparion occidentale Macdonald
1966Neohipparion occidentale Dalquest and Hughes
1975Neohipparion occidentale Forsten p. 65 figs. Tables 21, 38; Figs. 6, 7
1984Cormohipparion occidentale MacFadden p. 162 figs. 9, 17, 18, 22, 23, 118-120, 131-139, 149,150
1996Cormohipparion occidentale Dalquest et al.
1996Cormohipparion occidentale Woodburne p. 16
1998Cormohipparion occidentale MacFadden p. 549
2007Cormohipparion occidentale Woodburne
2011Cormohipparion occidentale Boessenecker p. 2
2019Cormohipparion occidentale May

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RankNameAuthor
kingdomAnimalia()
—Bilateria
—EubilateriaAx 1987
—Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
—Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
—Tetrapoda
—Reptiliomorpha
—Anthracosauria
subclassAmphibiosauriaKuhn 1967
—Cotylosauria()
—Amniota
subclassSynapsida
—Therapsida()
infraorderCynodontia()
—Mammaliamorpha
—Mammaliaformes
classMammalia
RankNameAuthor
—Theriamorpha(Rowe 1993)
—Theriiformes()
—Trechnotheria
—Cladotheria
—Zatheria
subclassTribosphenida()
subclassTheria
—Eutheria()
—Placentalia
—Boreoeutheria
—Laurasiatheria
—Scrotifera
—Euungulata
—Panperissodactyla
superorderPerissodactylamorpha
orderPerissodactyla()
superfamilyEquoidea
familyEquidae
subfamilyEquinae
tribeHipparionini
genusCormohipparion
speciesoccidentale()

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.

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Invalid names: Hipparion mohavense Merriam 1913 [synonym], Hipparion mohavense callodonte Merriam 1915 [synonym], Hipparion platystyle Merriam 1915 [synonym]
Diagnosis
ReferenceDiagnosis
J. C. Merriam 1913 (Hipparion mohavense)Crowns of upper molars nearly straight; protocone small, separate from protoconule and nearly circular in cross-section; enamel of the fossettes very strongly crinkled; mesostyle of nearly uniform width.
H. F. Osborn 1918 (Hipparion mohavense) (Merriam, p. 436) (1) Crowns of upper molars nearly straight or but slightly curved, crowns not
very elongate, length about one and one-half times the transverse diameter, in less worn specimens crowns may equal about twice the transverse· diameter; (2) cement layer well developed on the outer and inner sides; (3) parastyle and mesostyle prominent, mesostyle especially strong on premolars, broadening toward the base; (4) outer sides of paracone and metacone may show a slight tendency to formation of a median rib, protocone, free almost to ba8e, nearly circular in cross section or slightly elongate anteroposteriorly; (5) anterior and posterior borders of pre- and postfossettes with numerous plications; (6) a pli caballin; (7) six or more short folds on either side of the metaloph, numerous folds also from the protoloph. (8) In dimensions and general form resembling H. richthofeni of China and H. gracile of Europe, lower cheek teeth also resembling those of H. richthofeni
H. F. Osborn 1918(Leidy, 1856, 1869, Gidley, 1907) (1) Protocone isolated, elliptical, anteroposterior diameter twice as
great as transverse; (2) protoconule, metaconule, and fossette borders of upper grinders comparatively complicated but lesssothaninEuropeantypes; (3)hypoconesmall,aboutone-halfthesizeoftheprotocone; (4)upperpremolarsrelatively elongate anteroposteriorly; (5) upper molars compared with premolars comparatively small; (6) tooth crowns long and slightly curved; (7) protocone of tmiform width throughout its length; (8) a much larger animal than Hipparion of South Carolina, approaching the H. gracile of Europe, and resembling in size, proportions, and curvature the teeth of Equus asinus.
H. F. Osborn 1918 (Hipparion platystyle)(Merriam, 1915, p. 5) (1) Crown large and well cemented; (2) form of the fossettes indicates that the crown was never greatly elongated; (3) protocone pillar small, distinct from the forked pli caballin, and somewhat flat- tened laterally; (4) fossettes narrower transversely than in H. 11Whavense; (5) enamel walls of fossettes plicate, para- and mesostyles heavy; (6) differing from H. mohavense in its more flattened protocone and narrower fossettes; (7) more nearly resembling the Hipparion forms of the Ricardo, especially in the specimen Univ. Cal. Pal. Coll. 19478.
A. -M. Forsten 1975(Leidy, 1856, 1869, Gidley, 1907, according to Osborn, 1918, revised and completed): Hypsodont. Protocone isolated, elliptical, antero- posterior diameter twice as great as transverse. Protoconule, metaconule and fossette borders complicated. Hypocone small, about half the size of the protocone. Molars compared to premolars small. Lower teeth with wide, flaring metaconid-metastylid column, low labial groove in the premolars, deep in the molars. Pli caballinid and parastylid well developed, additional plica- tions in flexids common.
B. J. MacFadden 1984Same as for genus with the following specific characters. Large and hypsodont North American hipparion. Mean TRL 138.00 mm. Unworn or little-worn M1MSTHT ca. 37-43 mm. DPOF with moderately developed (ca.5mm or less) posterior pocket. Protocones oval and relatively elongate. Fossette borders most plicated of all North American hipparions. In the lower premolars, shallow ectoflexids and moderately developed pli caballinids. In the lower molars, deep ectoflexids and pli caballinids rudimentary or absent. Protostylids well developed and sometimes isolated. Elongate, expanded, and large metaconids, metastylids, entoconids, and hypoconulids with rounded or angular borders.
Cormohipparion occidentale is similar to Neohipparion affine and N. leptode in size. This species differs from other horse genera in the generic characters. Cormohipparion occidentale differs from both C.goorisi and C. sphenodus in larger size, higher crowns, more elongated protocones, significantly increased complexity of enamel plications (particularly on fossette borders), and more expanded metaconids, metastylids, entoconids, and hypoconulids often times with angular enamel borders.
M. O. Woodburne 2007Based on the type and referred material, within the subgenus Cormohipparion, C. occidentale is distin- guished from C. goorisi and C. quinni (fig. 9) in larger cranial (and presumably body) size; in higher crowned cheek teeth; in having a more complex enamel pattern in the upper cheek teeth; in dP1 being reduced to absent; in lower cheek teeth with stronger protostylids; in a cranium with the DPOF having a generally teardrop shape (dorsoven- trally much higher posteriorly than anteriorly); and in the lacrimal not reaching the rear of the DPOF.
With respect to other members of the C. occidentale group, C. occidentale, s.s., is distinguished in having 4–5 plis on the anterior border of the molar prefossette. The molar posterior border of the prefossette has 8–9 plis; the premolar posterior border of the postfossette has 2–3 plis; the molar posterior border of the postfossette has 2– 3 plis; the molars usually have two plis caballin; and the orbit is posterior to M3. With a range of about 50–66mm, the unworn MSTHT for P3–M3 is higher than that for all other species, possibly except C. skinneri, n.sp. (table 3B), a segregation strengthened by a comparison of unworn MSTHT for P4/M1 in these samples, as well.
In addition, and as compared in figures 13, 15, 18, 20, 22, and 24, C. occidentale has the most deeply incised nasal notch (no. 30) of all the other species, and the lacrimal does not extend anteriorly beyond the junction with the maxillo-jugal suture, in contrast to C. merriami, n.sp., and C. johnsoni, n.sp., but not C. fricki, n.sp., C. matthewi, n.sp., or C. skinneri, n.sp. As in C. matthewi, n.sp., the lacrimal in C. occidentale extends across about 60% of the POB (table 3A), greater than all other species except C. skinneri, n.sp., and C. johnsoni, n.sp. Cormohipparion occi- dentale also has a longer muzzle (parameter 1) than all members of the Cormohipparion group but C. merriami, n.sp. The 1 S.D. (standard deviation) range of the length of the DPOF (no. 33) in C. occidentale incor- porates the (low) range of this feature seen in C. merriami, n.sp., and C. skinneri, n.sp., so these populations probably are not distinct in this regard. However, the DPOF is sharply shorter in C. matthewi, n.sp., and C. johnsoni, n.sp., and its 1 S.D. ranges are much smaller in C. fricki, n.sp. None of the other species shows as tall a DPOF (no. 35) as in the Machaerodus and Hans Johnson quarry samples of C. occidentale, and only C. johnsoni, n.sp., has as short a separation of the DPOF and facial crest (no. 36) as in those two quarry samples of C. occidentale.
Measurements
No measurements are available
Composition: phosphaticsubp
Environment: terrestrialsubc
Locomotion: actively mobilec
Life habit: ground dwellingsubf
Diet: grazerg
Diet 2: browserg
Reproduction: viviparoussubc
Created: 2009-01-04 10:23:13
Modified: 2009-01-04 12:58:34
Source: g = genus, subf = subfamily, subc = subclass, c = class, subp = subphylum
References: Carroll 1988, MacFadden and Cerling 1996, Hendy et al. 2009, Ji et al. 2002, Lillegraven 1979, MacFadden 1998

Age range: base of the Barstovian to the top of the Early/Lower Clarendonian or 16.30000 to 9.40000 Ma

Collections (24 total)


Time interval Ma Country or state Original ID and collection number
Barstovian16.3 - 12.5USA (New Mexico) Cormohipparion occidentale (19470)
Clarendonian12.5 - 9.4USA (California) Cormohipparion occidentale (19322 19323 19384)
Clarendonian12.5 - 9.4USA (Nebraska) Cormohipparion occidentale (18037 18092 18135 18218 18242 18466 188779) Hippotherium occidentale (18214 18245 18496) Hippotherium sp. (18324)
Clarendonian12.5 - 9.4USA (South Dakota) Neohipparion occidentale (18481)
Early/Lower Clarendonian12.5 - 9.4USA (Florida) Cormohipparion occidentale (161374)
Late/Upper Clarendonian12.5 - 9.4USA (New Mexico) Cormohipparion occidentale (19528)
Late/Upper Clarendonian12.5 - 9.4USA (Nebraska) Cormohipparion occidentale (18327)
Clarendonian - Pliocene12.5 - 2.588USA (Oklahoma) Cormohipparion occidentale (170180)
Tortonian11.62 - 7.246USA (California) Hipparion mohavense (46070)
Late/Upper Miocene11.608 - 5.333USA (California) Hipparion mohavense (19554)
Late/Upper Miocene - Pliocene11.608 - 2.588USA (California) Hipparion platystyle (19609)
Hemphillian10.3 - 4.9USA (Texas) Cormohipparion occidentale (18072)