Definition

Noun: 1. An extinct class of armored, jawed fishes: A placoderm is a member of an extinct group (class Placodermi) of prehistoric, fish-like vertebrates. They are characterized by having bony plates of armor covering the head and the front part of their body. 2. A key fossil from the Paleozoic Era: Placoderms were the dominant aquatic vertebrates during the Devonian period (often called the "Age of Fishes") and are significant in evolutionary history as they are considered among the earliest vertebrates to have evolved jaws.

Usage Examples

• Noun:
  • The museum's fossil collection includes a remarkably complete placoderm specimen.
  • Scientists study placoderm fossils to understand the early evolution of jaws and paired fins.
  • Dunkleosteus was a massive and fearsome placoderm that lived during the Late Devonian.

Advanced Usage

• In paleontological context: The term is used precisely to refer to this specific taxonomic class. It is often discussed in contrast to other early fish groups like ostracoderms (jawless armored fish) and acanthodians (often called "spiny sharks").
  • The discovery provided new insights into the diversity and anatomy of placoderms.

Variants and Related Words

• Placodermi (n): The scientific class name for the group containing all placoderms.
• Placodermal (adj): Relating to or characteristic of placoderms.
  • The placodermal armor was composed of large, interlocking plates.

Synonyms

• Armored fish (general descriptive term)
• Devonian fish (temporal descriptive term)

Related Phrases/Concepts

• Bony plate: A key physical characteristic of placoderms.
• Gnathostome: A vertebrate with jaws; placoderms are considered early gnathostomes.
• Devonian extinction: The event at the end of the Devonian period during which placoderms became extinct.

Noun

1. fish-like vertebrate with bony plates on head and upper body; dominant in seas and rivers during the Devonian; considered the earliest vertebrate with jaws