# acanthodian

CEFR C2 · Noun

Source: https://englishreference.com/word/acanthodian
Updated: 2026-05-26

## Definition

a type of ancient fish that lived in the oceans millions of years ago. These fish had a unique body shape and were some of the first animals to have jaws.

For teachers: a member of an extinct group of jawed fish that lived during the Silurian and Devonian periods. Characterised by a distinctive body shape and the presence of a single pair of gill slits.

## Examples

- The acanthodian is an early example of a jawed fish.
- Fossils of the acanthodian have been found in marine sediments, providing insight into the evolution of early vertebrates.
- The acanthodian represents a critical transitional stage in the development of modern fish, bridging the gap between jawless and fully developed jawed vertebrates.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.