1. The posterior body region of a trilobite, consisting of fused segments and a tail-like structure.
Usage: paleontology; zoology
2. The posterior abdominal region of certain arthropods, such as horseshoe crabs and some crustaceans.
Usage: zoology; technical

Examples

• The trilobite's pygidium was segmented and curved upward.
• Paleontologists identified the species by examining the shape of the pygidium.
• The pygidium of the horseshoe crab is a distinctive tail-like appendage.
• Fossil collectors often find isolated pygidia from ancient trilobites.
• The size and morphology of the pygidium vary significantly among trilobite species.