PBDB Taxon

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Equus (Hesperohippus) mexicanus

Mammalia - Perissodactyla - Equidae

Taxonomy

Equus (Hesperohippus) mexicanus was named by Hibbard (1955) [holotype = IGM 4009??; type of subgenus Hesperohippus; "taken from a Pleistocene deposit at Tajo de Tequixquiac, Estado de Mexico"]. Its type specimen is No. 48 (HV-3), Museo Nacional de Historia Natural, a skull (nearly perfect skull lacking the LM3), and it is a 3D body fossil.

It was synonymized subjectively with Equus pacificus by Lundelius (1972); it was synonymized subjectively with Equus giganteus by Kurten and Anderson (1980); it was synonymized subjectively with Equus laurentius by Winans (1989); it was recombined as Equus mexicanus by Pichardo (2004) and Alberdi et al. (2014).

Sister species lacking formal opinion data

E. algericus, E. altidens, E. bressanus, E. ferus, E. germanicus, E. helmei, E. hydruntinus, E. livenzovensis, E. marxi, E. mauritanicus, E. mosbachensis, E. namadicus, E. petraloniensis, E. robustus, E. simionescui, E. stehlini, E. valeriani, E. verae, E. helmei, E. koobiforensis, E. oldowayensis

Synonyms

Equus bautistensis was named by Frick (1921) [not mentioned by Kurten_&_Anderson 1980].

It was synonymized subjectively with Equus occidentalis by Kurten and Anderson (1980); it was synonymized subjectively with Equus scotti by Scott (1998).
Equus midlandensis was named by Quinn (1957). Its type specimen is T.M. no. 998, a partial skeleton (Right and left lower jaws, lack· ing M.2-3 on the right, M.3 on the left and the ascending rami; upper left P.2, right P.3M.l; right metatarsal III and navicu- ), and it is a 3D body fossil.

It was synonymized subjectively with Equus scotti by Lundelius (1972), Kurten and Anderson (1980) and Lundelius (1984); it was synonymized subjectively with Equus laurentius by Winans (1989) and Harris (1993); it was synonymized subjectively with Equus (Hesperohippus) mexicanus by Scott et al. (2003).
Equus occidentalis was named by Leidy (1865).

It was recombined as Amerhippus occidentalis by Hoffstetter (1950); it was synonymized subjectively with Equus (Dolichohippus) simplicidens by MacFadden (1998); it was considered a nomen dubium by Miller (1971) and Miller (1976); it was synonymized subjectively with Equus mexicanus by Alberdi et al. (2014).
Equus pacificus was named by Leidy (1868) [also said to be 1869]. It is a 3D body fossil.

It was synonymized subjectively with Equus occidentalis by Leidy (1873) and Schultz (1938); it was considered a nomen dubium by Savage (1951); it was synonymized subjectively with Equus mexicanus by Alberdi et al. (2014).
Equus scotti was named by Gidley (1900) [apparently accepted by all authors; see also Dalquest and Schultz 1992]. Its type specimen is AMNH 10606, a skeleton (a nearly complete skeleton (No. io6o6), consisting of the skull and lower jaws, the cervical ver- tebrae, the three anterior dorsal vertebre, both fore limbs an), and it is a 3D body fossil. Its type locality is head of Rock Creek, Mayfield Ranch, which is in an Irvingtonian terrestrial horizon in the Tule Formation of Texas.

It was synonymized subjectively with Equus mexicanus by Alberdi et al. (2014).
Onager oviedoi was named by Mooser (1959) [status unclear in light of Hulbert 1995b].

It was synonymized subjectively with Equus laurentius by Winans (1989); it was synonymized subjectively with Equus (Hesperohippus) mexicanus by Mooser and Dalquest (1975) and Scott et al. (2003).

Synonymy list

Year	Name and author
1865	Equus occidentalis Leidy p. 94
1868	Equus pacificus Leidy p. 195
1873	Equus occidentalis Leidy p. 242
1900	Equus scotti Gidley p. 111 figs. 1 - 5
1901	Equus occidentalis Gidley p. 114 fig. 10
1901	Equus pacificus Gidley p. 116 fig. 11
1901	Equus scotti Gidley p. 134
1902	Equus occidentalis Hay p. 623
1902	Equus pacificus Hay p. 623
1902	Equus scotti Hay p. 624
1921	Equus bautistensis Frick
1931	Equus pacificus Elftman p. 13
1950	Amerhippus occidentalis Hoffstetter
1952	Equus occidentalis Hoffstetter
1955	Equus (Hesperohippus) mexicanus Hibbard p. 66 figs. Pl. IV, Figs. 1-3; Fig. 5A-B)
1957	Equus midlandensis Quinn p. 24 figs. Pl. II, fig. 3; Pl. V, fig. 2; Pl. VI; Pl. VII, fig. 3
1957	Equus pacificus Quinn p. 27
1959	Onager oviedoi Mooser
1966	Equus midlandensis Slaughter p. 89
1972	Equus pacificus Lundelius, Jr.
1975	Equus (Hesperohippus) mexicanus Mooser and Dalquest
1980	Equus occidentalis Kurten and Anderson p. 289
1980	Equus pacificus Kurten and Anderson p. 289
1980	Equus scotti Kurten and Anderson p. 290
1987	Equus (Hesperohippus) mexicanus Carranza-Castaneda and Miller p. 339
1998	Equus scotti MacFadden p. 551
2003	Equus (Hesperohippus) mexicanus Scott et al.
2004	Equus mexicanus Pichardo p. 15
2014	Equus mexicanus Alberdi et al. pp. 227 - 229 figs. Figures 6 to 8

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
subclass	Synapsida
—	Therapsida	()
infraorder	Cynodontia	()
—	Mammaliamorpha
—	Mammaliaformes
class	Mammalia

Rank	Name	Author
—	Theriamorpha	(Rowe 1993)
—	Theriiformes	()
—	Trechnotheria
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Boreoeutheria
—	Laurasiatheria
—	Scrotifera
—	Euungulata
—	Panperissodactyla
superorder	Perissodactylamorpha
order	Perissodactyla	()
superfamily	Equoidea
family	Equidae
subfamily	Equinae
tribe	Equini
genus	Equus
subgenus	Hesperohippus
species	mexicanus

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.

†Equus (Hesperohippus) mexicanus Hibbard 1955

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Invalid names: Equus midlandensis Quinn 1957 [synonym], Onager oviedoi Mooser 1959 [synonym]

Diagnosis

Reference	Diagnosis
J. H. Quinn 1957 (Equus midlandensis)	Size and proportions of skeletal elements preserved, indistinguishable from E. caballus laurentius; teeth slightly larger, valley of metaconid-metastylid shallower and broader than E. cabalIus; median valley of lower molars shorter; upper cheek teeth with wider styles, less complex· enamel pattern, and more elongated protocones.
M. T. Alberdi et al. 2014	The skull is large. The basicranial length is greater than 500 mm at the available material. The narial notch is deep and extends over the commissure between P2 and P3. The rostrum is broad, the choanae rather narrow, the posterior palatine foramina are placed opposite the M3. The masseteric ridge is of medium length and curves downward rostrally. The upper cheek teeth are large, with elongate flattened protocones, derived features and average complexly plicate enamel. Lower molars have a shallow ectoflexid on premolars, penetrating the isthmus on m1, m2, and m3 in advance stage of wear. Following Winans (1989), the ratio of length to proximal width is generally less than 5.0 for metacarpals and 6.0 for metatarsals. Metapodials are not stilt-legged. The body mass from MCIII13 is between 354.33 and 532.88 kg and the mean is 456.23 kg.