Agnathans and the origin of jawed vertebrates

@article{Forey1993AgnathansAT,
  title={Agnathans and the origin of jawed vertebrates},
  author={Peter L. Forey and Philippe Janvier},
  journal={Nature},
  year={1993},
  volume={361},
  pages={129-134}
}
The origins of jawed vertebrates (gnathostomes) lie somewhere within the ranks of long-extinct jawless fishes, represented today as the lampreys and hagfishes. Recent discoveries of hitherto unknown kinds of jawless fishes (agnathans), together with re-examination of known agnathans and advances in systematic methods, have revitalized debates about the relationships of ancient fishes and given fresh insights into early vertebrate history. 
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