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(subphylum Echinozoa, class Echinoidea)

An order of irregular echinoids in which the apical system is elongated, but not disjunct. In the plastron, the labral plate is followed by a single, large plate, and a varying number of plates in a single column. The Holasteroida first appeared in the Early Cretaceous.

Subjects: Zoology and Animal Sciences.

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