Definition

1. Noun:
   • An extinct jawless fish of the Devonian period with an armored head: An "osteostracan" is a member of an extinct group of early, jawless vertebrates characterized by a bony, shield-like head armor.

Usage Examples

• Noun:
  • The fossil record shows that the osteostracan was a common aquatic organism during the Devonian period.
  • Scientists study the head shield of the osteostracan to understand early vertebrate evolution.

Advanced Usage

• In paleontological classification: The term "osteostracan" is used to refer to any member of the subclass Osteostraci.
  • Osteostracans are considered a sister group to jawed vertebrates.

Variants and Related Words

• Osteostraci (n): The scientific subclass name for this group of extinct jawless fishes.
  • Osteostraci is a key taxon for studying the origin of paired fins.

Synonyms

• Cephalaspid: A common synonym referring to the same group of extinct armored jawless fishes.

Different Meanings

• This word has a single, specific meaning in paleontology and evolutionary biology. It does not have common idiomatic or figurative uses.

Noun

1. extinct jawless fish of the Devonian with armored head