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Protohippus (Calippus)

Mammalia - Perissodactyla - Equidae

Synonymy list
YearName and author
1930Protohippus (Calippus) Matthew and Stirton
1937Calippus Johnston p. 905
1940Calippus Stirton p. 188
1955Calippus Quinn p. 27
1988Calippus Carroll
1988Calippus Hulbert, Jr. p. 231
1989Calippus Prothero and Schoch p. 532
1995Calippus Kelly p. 25
1996Calippus Prado and Alberdi p. 676
1998Calippus MacFadden p. 550
2019Calippus May

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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
genusProtohippus()
subgenusCalippus

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
J. H. Quinn 1955Animals of small size; cheek teeth strongly hypsodont; uppers slightly curved; ectoloph flattened, styles delicate, valleys shallow and ribbed; fos- settes tranversely compressed;· pli proto- loph and pli hypoloph reduced to absent; protocone oval, elongate and directed posterolingually, always connected with protoselene; hypoconal groove open to half the length of the crowns in early
. species, closed or nearly closed in late species; lower teeth with large metaconid, metastylid small and progressively re- duced, metaconid and metastylid sep- arated, intervening valley not deep but persistent; parastylid present but narrow and projecting a little forward; no pli caballinid; no protostylid on either milk or permanent teeth.
R. C. Hulbert 1988Very small to medium-sized equids, with toothrow lengths less than 140 mm. DPOF long, relatively shallow, not pocketed; or absent. Malar fossa absent. Muzzle region greatly expanded (width 45% or greater than UTRL), with relatively large 112/i12. First and second incisors positioned in a straight row of four teeth, with the I3/i3 angled sharply posteriorly. Postcanine diastema relatively short. Cheekteeth moderate to extremely hypsodont. Upper cheekteeth with elongate or oval protocones broadly connected to protoselene (very rarely isolated in early wear), generally simple fossettes with plications absent or limited to early wear-stages, and single, unbranched pli caballins that fade with wear and are typically much stronger on premolars than molars. Lower cheekteeth typically with relatively non-persistent lingual flexids, shallow premolar ectoflexids, and lacking plications (except for pli entoflexids in early wear-stages) and pli caballinids. Deciduous lower premolars lack ectostylids.