|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Mammalia - Perissodactyla - Equidae
It was reranked as Calippus by Johnston (1937), Stirton (1940), Quinn (1955), Hulbert (1988), Carroll (1988), Prothero and Schoch (1989), Kelly (1995), Prado and Alberdi (1996), MacFadden (1998) and May (2019).
It was assigned to Protohippus by Matthew and Stirton (1930); to Calippini by Quinn (1955); to Equidae by Johnston (1937), Stirton (1940) and Carroll (1988); to Protohippini by Kelly (1995); to Protohippina by Hulbert (1988) and Prado and Alberdi (1996); and to Equini by Prothero and Schoch (1989), MacFadden (1998) and May (2019).
|Year||Name and author|
|1930||Protohippus (Calippus) Matthew and Stirton|
|1937||Calippus Johnston p. 905|
|1940||Calippus Stirton p. 188|
|1955||Calippus Quinn p. 27|
|1988||Calippus Hulbert, Jr. p. 231|
|1989||Calippus Prothero and Schoch p. 532|
|1995||Calippus Kelly p. 25|
|1996||Calippus Prado and Alberdi p. 676|
|1998||Calippus MacFadden p. 550|
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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.
|J. H. Quinn 1955||Animals 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 1988||Very 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.|