n.eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms

同義詞：jawless vertebratejawless fish

1. The study of agnathans provides insight into the early evolution of vertebrates.
   對無頜類的研究為脊椎動物的早期進化提供了見解。
2. Agnathans lack true jaws, which distinguishes them from more advanced vertebrates.
   無頜類缺乏真正的頜骨，這使它們與更進化的脊椎動物區(qū)別開來。