cyclostome

This term is a specialized biological classification used primarily in ichthyology and zoology. It describes a specific anatomical feature—the circular, jawless mouth—which distinguishes these primitive vertebrates from gnathostomes, the jawed vertebrates. Because of its technical nature, the word is rarely encountered outside of scientific literature, textbooks, or academic discussions regarding evolutionary biology.

In a taxonomic context, the term refers to the group containing lampreys and hagfish. It is used as a descriptive noun to categorize these organisms based on their shared morphological characteristics rather than their behavioral traits.