|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Merychippus isonesus tertius
Mammalia - Perissodactyla - Equidae
It was recombined as Merychippus (Protohippus) tertius by Stirton (1940); it was recombined as Acritohippus tertius by Kelly (1995) and Kelly (1998); it was recombined as Merychippus tertius by Hulbert and MacFadden (1991) and MacFadden (1998).
|Year||Name and author|
|1918||Merychippus isonesus tertius Osborn p. 105 figs. Plates 13.5,6, 14.3, 41.2, 46.2, 52.2. Text Fig. 80|
|1940||Merychippus (Protohippus) tertius Stirton p. 181|
|1991||Merychippus tertius Hulbert, Jr. and MacFadden p. 33|
|1995||Acritohippus tertius Kelly p. 9|
|1998||Acritohippus tertius Kelly|
|1998||Merychippus tertius MacFadden p. 547|
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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.
|H. F. Osborn 1918|| (Matthew, 1913, Osborn, 1918) (1) This type is slightly larger than the preceding. (2) Crochetuniting
with protoconule in half worn teeth, giving off a prominent internal fold, or pli caballin; (3) protocone a long oval, uniting by a strong interior spur with middle compression of protoconule crescent in half worn teeth; (4) prominent plications of the metaloph entering pre- and postfossettes; (5) rudiments of the second plication. (6) Limb bones as in M. isonesus secundus, but shafts more robust than in the preceding type; (7) shafts of lateral digits as in M. isonesus secundus; (8) ulna fused for a short distance with radius. This type is separable from M. isonesus secundus in the antero-posterior elongation of the protocone. It is a premutation which is closely united to the preceding but shows a slight advance in the pli caballin, in the early union of protoconule and crochet, and the somewhat greater anteroposterior elongation of the protocone. The referred specimen, Amer. Mus. 14183, a topotype, exhibits the manner in which all the enamel plications and folds disappear in much worn crowns.