| Word | Definitions | Synonyms |
|---|---|---|
| eohippus | (noun) earliest horse; extinct primitive dog-sized four-toed Eocene animal | Synonyms: dawn horse |
| mesohippus | (noun) North American three-toed Oligocene animal; probably not directly ancestral to modern horses | - |
| pappus | (noun) calyx composed of scales or bristles or featherlike hairs in plants of the Compositae such as thistles and dandelions | - |
| protohippus | (noun) Pliocene horse approaching donkeys in size | - |