Zuniceratops (“Zuni horned face”) was discovered in New Mexico, USA, and dates to the Late Cretaceous (~91 mya). Estimated to have been about 3.5m long (11′5″), it was one of the earliest ceratopsians with well-developed horns over its eyes.
It had a transitional mix of features between basal ceratopsians and the later larger forms – having brow horns and a long narrow snout, but a frill lacking decorative scalloped edges – suggesting that the horned ceratopsids evolved from more “primitive” ancestors already within North America rather than migrating in later from Asia.
Bones from several different individuals have been found, showing that their teeth became more firmly rooted with age, going from single-rooted in juveniles to double-rooted in adults. The brow horns also appear to have grown continuously throughout Zuniceratops’ life, with those of older specimens being much larger.