Ornithischians

Part of speech: noun

Definitions

1. A category of dinosaurs characterized by a pelvic structure similar to birds and primarily herbivorous diet
2. Dinosaurs that share a distinctive hip arrangement and generally consume plants
3. Herbivorous dinosaurs distinguished by their bird-like pelvis anatomy and diet

Etymology: "Ornithischians" is the plural of "ornithischian", a noun for a dinosaur belonging to the group Ornithischia. The group's name combines Greek "ornis" (bird) and "ischion" (hip joint), a label that looks odd at first because these dinosaurs are not closely related to birds. The name refers to a hip arrangement that the early paleontologists who named the group thought resembled that of birds, with the pubis bone pointing backward alongside the ischium, a resemblance that modern studies show is a case of convergent evolution rather than shared ancestry. The suffix "-an" is the common English ending that turns a group name into a noun for one of its members, as in "Darwinian" or "Lutheran" style formations. Words like this one were built in the scientific world rather than handed down through everyday speech, so the story is one of deliberate naming, not gradual change.