Evolution of myelin sheaths: Both lamprey and hagfish lack myelin

@article{Bullock1984EvolutionOM,
  title={Evolution of myelin sheaths: Both lamprey and hagfish lack myelin},
  author={Theodore Holmes Bullock and Jean K. Moore and R. Douglas Fields},
  journal={Neuroscience Letters},
  year={1984},
  volume={48},
  pages={145-148}
}
Modern views of agnathan phylogeny consider Petromyzoniformes and Myxiniformes to belong to distinct classes that diverged from a common ancestor at a remote period, perhaps in the lower Cambrian, greater than 600 million years ago. Both are more primitive than elasmobranchs, holocephalans and bony fishes. Myelin is well developed in elasmobranchs and other fishes but was reported to be lacking in the spinal cord of lampreys. In order to search further for possible early myelin in some part of… Expand
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