Pachycephalosaurids

Part of speech: noun

Definitions

1. Herbivorous dinosaurs from the Cretaceous period characterized by a remarkably thick, domed skull roof that may have been used in intraspecies combat
2. A group of bipedal dinosaurs known for their unusually dense and heavily reinforced cranial bones, thought to have engaged in head-butting behavior
3. Cretaceous-era dinosaurs distinguished by their solid, enlarged skull structures and bipedal locomotion, believed to have utilized their reinforced heads as weapons during conflict

Etymology: Every part of this word is Greek. "Pachys" means thick, "kephalē" means head, and "sauros" means lizard. Together they describe the group's most striking feature: a dome of bone on top of the skull, in some species very thick. Scientists coined the name from these classical roots, so no ancient Greek ever used it. The ending "-ids" is the English plural of "-id," the suffix zoologists use for family-level groups, taken from the Latin-style "-idae." The word therefore names a family of dinosaurs. Its best-known member, "Pachycephalosaurus," takes the singular "-saurus" ending and gives the family its common name.