agnatha

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

同义词：superclass Agnatha

1. Agnatha represents the most primitive group of vertebrates in the evolutionary tree.
   无颌类纲代表了进化树中最原始的脊椎动物群体。
2. The study of Agnatha helps scientists understand the early development of vertebrate features.
   研究无颌类纲有助于科学家理解脊椎动物特征的早期发展。