Ostracoderms

Definition

Ostracoderms are extinct, jawless fish-like vertebrates that lived during the Paleozoic era. They are among the earliest known vertebrates and had bony armor covering their bodies.

5 Must Know Facts For Your Next Test

1. Ostracoderms existed approximately 450 to 350 million years ago.
2. They lacked jaws and paired fins but had a cartilaginous skeleton.
3. Ostracoderms are often considered the ancestors of modern jawed vertebrates.
4. Their bony armor served as protection against predators.
5. Fossils of ostracoderms have been found in both freshwater and marine environments.

Review Questions

• What era did ostracoderms live in?
• What kind of skeleton did ostracoderms possess?
• How did ostracoderms' bony armor benefit them?

Related terms

Agnatha:

A superclass of jawless fish that includes both living species like lampreys and extinct species such as ostracoderms.

Placodermi: An extinct class of armored prehistoric fish known for having jaws, unlike ostracoderms.

Chordata:

The phylum that includes all vertebrates, characterized by having a notochord at some stage of development.