Cyathea cranhamii sp. nov. (Cyatheaceae), anatomically preserved tree fern sori from the Lower Cretaceous of Vancouver Island, British Columbia.

Permineralized cyatheaceous sori occur among remains of conifers, fungi, and other plants in newly discovered calcareous concretions from Early Cretaceous (Barremian) marine sediments of Vancouver Island, British Columbia, Canada. Sori are superficially attached in two rows to narrow pinnules and display a globose sphaeropteroid indusium. Annulate sporangia with multicellular stalks diverge from a basal, vascularized receptacle. The nearly vertical uniseriate annulus is not interrupted by the stalk. The sporangia bear 64 trilete spores with perispore sculpturing that ranges from irregular granulate/echinate to prominent rodlets. These specimens, described as Cyathea cranhamii sp. nov., are the first anatomically preserved tree fern sori from the fossil record. They represent the most ancient evidence for fertile structures of the Cyatheaceae and demonstrate that essentially modern species of cyatheaceous tree ferns had evolved by the Early Cretaceous.