'Protohippus' definitions:
Definition of 'protohippus'
(from WordNet)
noun
Pliocene horse approaching donkeys in size
Definition of 'Protohippus'
From: GCIDE
- Protohippus \Pro`to*hip"pus\, n. [NL., from Gr. ? first + ? horse.] (Paleon.) A genus of fossil horses from the Lower Pliocene. They had three toes on each foot, the lateral ones being small. [1913 Webster]