Complex sentence: The most different from "Merychippus" was "Hipparion", mainly in the structure of tooth enamel: in comparison with other Equidae, the inside, or tongue side, had a completely isolated parapet.
Split into simpler sentences: The most different from "Merychippus" was "Hipparion". The main difference was in the structure of tooth enamel: in comparison with other Equidae, the inside, or tongue side, had a completely isolated parapet.