Mearas

The Mearas were a breed of wild horses in the north of Middle-earth. Their mortality is equal to Men and their intelligence and strength are extraordinary.
They descended from Felaróf, who was tamed by the first King of Rohan, Eorl. Ever since, they have been the mounts of the King and Princes of Rohan alone. During the War of the Ring, however, Gandalf the Grey tamed Shadowfax, lord of the Mearas at the end of the Third Age.