Plagiolophus annectans
Late Eocene (Ludian)
Gard, France

230mm skull with 175mm half mandible of this early horse.

From Wikipedia: Palaeotheriidae (Opens in new tab)

See: DEPERET C., 1917, MONOGRAPHIE DE LA FAUNE DE MAMMIFERES FOSSILES DU LUDIEN INFERIEUR D’EUZET LES BAINS (GARD), ANNALES DE L’UNIVERSITE DE LYON,N.S.I SCIENCES MEDECINE FASC.40