Probing the cassiduloid origins of clypeasteroid echinoids using stratigraphically restricted parsimony analysis

  title={Probing the cassiduloid origins of clypeasteroid echinoids using stratigraphically restricted parsimony analysis},
  author={Andrew B.T. Smith},
  • A. Smith
  • Published in Paleobiology 1 March 2001
  • Geography
Abstract Clypeasteroid echinoids are a familiar and easily defined clade with a cryptic origin. They first appear in the late Paleocene and are believed to have arisen from cassiduloid ancestry, but identifying sister-group relationships more precisely has proved difficult. Two factors are responsible for this problem, the extreme morphological conservatism of cassiduloids, which has given rise to high levels of character exhaustion, and the origin of crown-group clypeasteroids through… 

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