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zonule Subdivision of a subzone based essentially on the presence of a given species. Several zonules are recognized, for example, in the Upper Cambrian Franconia Sandstone of Minnesota. Here the zone was recognized by the presence of the trilobites (Trilobita) Ptychaspis and Prosaukia, the subzone by Prosaukia, and zonules by Prosaukia striata and P. granulosa.

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zonule (zonula) (zon-yool) n. (in anatomy) a small band or zone. z. of Zinn (zonula ciliaris) the suspensory ligament of the lens of the eye.
zonular adj.