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(Cycadofilicales, seed ferns) An extinct order of gymnosperms known from fossils of the Devonian to Triassic periods. Although they had fernlike fronds, similar to those of the fern order Marattiales, their stems show secondary thickening and more significantly there is evidence of seed formation. The ovules were not borne in strobili but developed along the margins or on the surface of megasporophylls, similar to the foliage leaves. Their seeds were characteristically radially symmetrical, a feature shared by the Cycadales, Bennettitales, and Caytoniales, and thought to indicate that these orders possibly originated from the Pteridospermales.
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