• Robert L. Carlton


an order of late Paleozoic freshwater sharks in the superorder Euselachii; formerly called Pleuracanthodii. Eellike and as long as 13 feet, the Xenacanthida are distinguished by two-pronged teeth and a large serrated spine extending backward from the rear of the braincase. They appeared in the Carboniferous and spread worldwide in the Permian, but only a few genera survived the Permian extinctions before disappearing in the Middle Triassic.

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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Robert L. Carlton
    • 1
  1. 1.SalemUSA

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