PLACODERMS Armor-Plated Fish of the Devonian

As a young boy growing up in fossil-rich western New York, I would spend untold hours walking the rocky outcrops of the Niagara Escarpment, the shore of an ancient Silurian Sea, collecting hundreds of marine fossils including Brachiopods and Crinoids.

- JOSEPH "PALEOJOE" KCHODL

The joy of discovery spurred me to learn more. Who knew my road would lead me to Michigan? Some 40 years later in northern Michigan, I happened upon a fossil I had never seen. Little did I know of the wonder and amazement of finding armor-plated fish with a hammer and chisel.

PLACODERM TYPES

Placoderms are some of the best-known fish of the ancient seas because of their hard dermal plates. “Placo” means plate and “derm” means skin. These fish had hard plates on their head section and the part of the thorax just behind the head. They also sported large flat bony plates. Since soft tissue generally does not fossilize, these plates are usually the only evidence we are able to find. They were a group of now-extinct prehistoric jawed fish that were abundant in ancient seas.

The Placoderms occupied two major subgroups: Arthrodires and Antiarchs.

Arthrodire Placoderms are the most well-known and abundant Placoderm fossils found. They are known for a movable joint between the head and body. In fact, Arthrodire is Greek for “jointed neck.”

Antiarchs are less common and more flattened. The Antiarchs also generally had armor-plated pectoral fins and a “box-shaped” head.