Stephanospermum braidwoodensis: nucellus & megaspore membrane

A reconstruction, based on microtomography, of the nucellus and megaspore membrane of a new fossil pteridosperm ovule (Stephanospermum braidwoodensis FMNH P30420) from Mazon Creek in Illinois as described by Alan Spencer, Jason Hilton and Mark Sutton in the journal Review of Palaeobotany and Palynology.

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