原恐角兽（Prodinoceras）是已知最早的犹因他兽科，生存于古新世晚期的蒙古。牠们亦被认为是犹因他兽类的基底，虽然牠有獠牙，但却未曾演化成顿角。

原恐角兽很像北美洲的原深颌兽。所有学者都认为原恐角兽是原深颌兽的姊妹分类。

Prodinoceras ("Before Terrible Horns") was the earliest known uintathere genus, which lived in the late Paleocene of Mongolia. It was a relatively small uintathere, reaching 2.9 m (9.5 ft) in length. It is also regarded as the most basal uintathere, as, although it had the characteristic fang-like tusks, it had yet to evolve the characteristic knob-like horns.