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Pliohippus (Pliohippus) mexicanus

Mammalia - Perissodactyla - Equidae

Taxonomy
Pliohippus (Pliohippus) mexicanus was named by Lance (1950). Its type specimen is CIT 3697, a maxilla, and it is a 3D body fossil. Its type locality is Yepomera, which is in a Hemphillian terrestrial horizon in Mexico.

It was recombined as Pliohippus mexicanus by Lance (1950) and Azzaroli (1966); it was recombined as Asinus mexicanus by Quinn (1955); it was recombined as Dinohippus mexicanus by May and Repenning (1982), MacFadden (1984), MacFadden (1986), MacFadden (1998) and Kelly (1998).

Synonyms
Synonymy list
YearName and author
1950Pliohippus mexicanus Lance
1950Pliohippus (Pliohippus) mexicanus Lance p. 35 figs. 4 - 10
1955Asinus mexicanus Quinn p. 52
1958Hippotigris ocotensis Mooser p. 360
1964Protohippus muelleri Mooser p. 157 figs. 1, 2
1966Pliohippus mexicanus Azzaroli
1973Dinohippus muelleri Mooser
1973Equus (Dolichohippus) mesamexicanus Mooser p. 261 figs. 7 - 12
1980Dinohippus ocotensis Dalquest and Mooser p. 8
1982Dinohippus mexicanus May and Repenning
1984Dinohippus mexicanus MacFadden p. 280
1986Dinohippus mexicanus MacFadden p. 468
1998Dinohippus mexicanus Kelly
1998Dinohippus mexicanus MacFadden p. 551

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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()
infraorderCynodontia()
RankNameAuthor
Epicynodontia
infraorderEucynodontia
Probainognathia
Mammaliamorpha
Mammaliaformes
classMammalia
subclassTribosphenida()
infraclassEutheria()
Placentalia
orderPerissodactyla()
suborderLophodontomorpha
infraorderEuperissodactyla
Hippomorpha
superfamilyEquoidea
familyEquidae
subfamilyEquinaeSteinmann and Döderlein 1890
tribeEquini
genusPliohippus
subgenusPliohippus
speciesmexicanus

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
B. J. MacFadden 1984The following is translated and para- phrased from Lance (1950:35-36): Size similar to Pliohippus osborni and "Pliohippus" interpolatus. The upper cheek teeth have slightly to moderately curved crowns, similar to Pliohippus osborni and less than Pliohippus interpolatus. The protocone is usually large and elongated, with a well developed anterior projec- tion; the lingual flexid varies from weak to pronounced, similar to species of Plesippus. The styles are moder- ately or strongly developed. The fossettes are crescent- shaped ("half-moon"), more so than in Pliohippus osborni. The fossette plications are moderately devel- oped in early wear stages. The postprotoconal valley is deep; the pli caballin can either be present or absent. The lower cheek teeth have rounded metaconids and rounded or angular metastylids. The metaconids and metastylids remain well separated until late wear stages; the linguaflexid is V-shaped. The protoconids and hy- poconids are flattened [relative to e.g., primitive plio- hippines]. A pli caballinid is sometimes present during early wear stages. The stylids [particularly the proto- stylid] vary from present to absent.
In addition, based on the present reappraisal of this species, D. mexicanus is characterized by a moderately developed nasomaxillary ("lacrimal" ofsome workers) fossa and no malar fossa.