Head and backbone of the Early Cambrian vertebrate Haikouichthys

@article{Shu2003HeadAB,
  title={Head and backbone of the Early Cambrian vertebrate Haikouichthys},
  author={De-gan Shu and Simon Conway Morris and J. Han and Z.-F. Zhang and Kinya Yasui and Philippe Janvier and L. Chen and X-L. Zhang and J.-N. Liu and Y. Li and H.-Q. Liu},
  journal={Nature},
  year={2003},
  volume={421},
  pages={526-529}
}
Agnathan fish hold a key position in vertebrate evolution, especially regarding the origin of the head and neural-crest-derived tissue. In contrast to amphioxus, lampreys and other vertebrates possess a complex brain and placodes that contribute to well-developed eyes, as well as auditory and olfactory systems. These sensory sytems were arguably a trigger to subsequent vertebrate diversifications. However, although they are known from skeletal impressions in younger Palaeozoic agnathans… 
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