Temporal range: Ypresian
|Restoration by Heinrich Harder c. 1920|
Eohippus is an extinct genus of small equid ungulates. The only species is E. angustidens, which was long considered a species of Hyracotherium. Its remains have been identified in North America and date to the Early Eocene (Ypresian) stage.
In 1876, Othniel C. Marsh described a skeleton as Eohippus validus, from the Greek ἠώς (eōs, "dawn") and ἵππος (hippos, "horse"), meaning "dawn horse". Its similarities with fossils described by Richard Owen were formally pointed out in a 1932 paper by Sir Clive Forster Cooper. E. validus was moved to the genus Hyracotherium, which had priority as the name for the genus, with Eohippus becoming a junior synonym of that genus. Hyracotherium was recently found to be a paraphyletic group of species, and the genus now includes only H. leporinum. E. validus was found to be identical to an earlier-named species, Hyracotherium angustidens (Cope, 1875), and the resulting binomial is thus Eohippus angustidens.
Stephen Jay Gould comments
In his essay, "The Case of the Creeping Fox Terrier Clone", Stephen Jay Gould lamented that the same arcane phrase ("the size of a small Fox Terrier"), when most readers would be not be closely familiar with size of a Fox Terrier. Gould concluded that Henry Fairfield Osborn had described it that way in a widely distributed pamphlet. The reasons for this comparison are unclear, but Gould proposes that Osborn, a keen fox hunter, could have made a natural association between horses and the dogs that accompany them. Eohippus was approximately 12 inches high at the shoulder, comparable to a Fox Terrier, which is up to 13 inches high at the shoulder.
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- MacFadden, B. J. (March 18, 2005). "Fossil Horses--Evidence for Evolution". Science. 307 (5716): 1728–1730. doi:10.1126/science.1105458. PMID 15774746.
- Froehlich, D. J. (2002). "Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla)". Zoological Journal of the Linnean Society. 134 (2): 141–256. doi:10.1046/j.1096-3642.2002.00005.x.
- Gould, S.J. (1991). "Essay 10: The case of the creeping fox terrier clone". Bully for Brontosaurus: Reflections in Natural History. W.W. Norton & Co.
- "Hyrocotherium (Eohippus)". University of Guelph.
- "Fox Terrier (Vital Stats)". DogTime.