zygopterid

plural zygopterids

1. A member of the Zygopterideae, an extinct family of ferns within order Osmundales having three-dimensional fronds with pinnae in four ranks and a rachis that is radially symmetrical in cross section.

   As in the zygopterids, the fronds of the coenopterids were […]

   1992, Peter Robert Bell, Green Plants: Their Origin and Diversity, page 196

   1 more example

   Phillips and Galtier (2005) also suggested that the ancestral form of the zygopterids was arborescent, based on the fact that the earliest forms (clepsydroid types) are arborescent.

   2009, Edith L. Taylor, Thomas N. Taylor, Michael Krings, Paleobotany: The Biology and Evolution of Fossil Plants, page 417