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How did Triceratops fit into dinosaur classification?

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Illustration showing various dinosaur species drawn to scale and grouped by geologic era: Late Cretaceous, Early Cretaceous, Jurassic, and Triassic. Dinosaurs range from large species like Brachiosaurus and Tyrannosaurus to smaller ones like Velociraptor and Compsognathus, with a human silhouette included for size comparison. Measurement bars at the bottom indicate 1 meter and 3 feet for scale reference. — dinosaur A selection of dinosaurs grouped by the geologic interval in which they lived.

Triceratops is classified as a member of the Ornithischia, one of the two major orders of dinosaurs, distinguished by their "bird-hipped" pelvic structure. Within this order, Triceratops belongs to the subgroup Cerapoda and more specifically to the Ceratopsia, a group of herbivorous dinosaurs defined by a bony frill on the back of the skull and a unique rostral bone at the tip of the upper beak.123

Within the Ceratopsia, Triceratops is categorized under the family Ceratopsidae, which includes horned dinosaurs with large frills. It is further placed within the subfamily Chasmosaurinae, a lineage characterized by large horns above the eyes and smaller nose horns.34