1. Plural of ostracoderm; any of various extinct jawless fish of the Paleozoic era that had bony or armored plating covering the head and front of the body.
Usage: paleontology; plural form; also called armored fish

Examples

• Ostracoderms were among the earliest vertebrates to appear in the fossil record.
• The ostracoderms dominated freshwater and marine environments during the Ordovician and Silurian periods.
• Scientists study ostracoderms to understand the evolution of early fish.
• Unlike modern fish, ostracoderms lacked true jaws and paired fins.
• The bony plates of ostracoderms provided protection from predators in ancient seas.