agnatha

Thân thiện

A lamprey, a member of the agnatha, swims in a freshwater stream.

Definition

1. Noun:
   • A superclass of jawless vertebrates: Agnatha is a taxonomic superclass comprising primitive, eel-shaped chordates that lack jaws and paired fins (like pelvic fins). This group includes living forms such as lampreys and hagfishes, as well as numerous extinct species.

Usage Examples

• Noun:
  • Lampreys and hagfishes are the only surviving members of the Agnatha.
  • The fossil record shows that Agnatha were once much more diverse.
  • Biologists study Agnatha to understand early vertebrate evolution.

Advanced Usage

• In taxonomic context: Used scientifically to classify a major group of vertebrates distinct from jawed vertebrates (Gnathostomata).
  • The division between Agnatha and Gnathostomata marks a key evolutionary step.

Variants and Related Words

• Agnathan (noun/adjective): A member of the Agnatha; relating to the Agnatha.
  • The agnathan fossil was remarkably well-preserved.
• Cyclostomata: A term sometimes used synonymously with Agnatha, referring specifically to the living jawless fishes (lampreys and hagfishes).

Synonyms

• Jawless fishes (common descriptive term, though not all agnathans are technically "fishes" in the common sense).
• Cyclostomes (for the extant members).

Notes on Meaning

• The term Agnatha is used almost exclusively in scientific (zoological and paleontological) contexts. It refers to an anatomical characteristic (the absence of jaws) that defines the group. It is not used in everyday language.

Học thuật

Noun

1. superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys; hagfishes; some extinct forms

Từ đồng nghĩa

• Agnatha
• superclass Agnatha