Ostracoderms

Part of speech: noun

Definitions

1. A group of extinct jawless fish characterized by a bony exterior and a lack of paired fins, living mainly in the Paleozoic era
2. An ancient class of fish known for their armored bodies and primitive features, existing prior to the development of jaws
3. A category of prehistoric vertebrates distinguished by their unique shell-like structures and presence in marine environments during early geological periods

Etymology: Ostracoderms are named for their armour, and the name is a compound of two Greek words meaning "shell" and "skin". The first part, "ostrakon", originally meant a broken piece of pottery, a shard, and it was also used for the shell of a shellfish or tortoise. The second, "derma", meant skin or hide. Put together, the name describes a fish whose body was covered in hard, shell-like plates rather than scales. The term was built in New Latin, the scientific Latin used by naturalists to name new discoveries, so no ancient Greek writer ever used it. Scientists drew on the classical "ostrakon" and "derma" to coin a label for these early fishes, which lived long before the fish with true jaws appeared.