The Triceratopsini branch of the chasmosaurs first split off somewhere around 75 million years ago, with Titanoceratops being the earliest known member. But they don’t seem to have really diversified until several million years later, towards the very end of the Cretaceous 70-68 million years ago, around the time the centrosaurs had already mostly disappeared.
Regaliceratops (“royal horned face”) dates to about 68-67 million years ago, and is estimated to have measured around 5m long (16’4″). Known from a single near-complete skull discovered in Alberta, Canada, the fossil specimen was nicknamed “Hellboy” for both its stubby brow horns and the immense difficulty of removing it from the surrounding rock.
It had highly unusual ornamentation for a chasmosaur – a long nose horn, short brow horns, and large crown-like spikes ringing its relatively short frill – convergently resembling the sort of arrangement seen in many centrosaurs.