Relationships among Fossil and Living Dipteridaceae: Anatomically Preserved Hausmannia from the Lower Cretaceous of Vancouver Island

Anatomically preserved foliage of a dipteridaceous fern has been identified in both calcareous nodules and fine-grained, carbonate-cemented sandstone from the early Cretaceous (Hauterivian-Barremian) Apple Bay locality from Vancouver Island, British Columbia, Canada. Fronds with attached sporangia containing spores are preserved as both compression/impressions and as permineralizations. Fan-shaped laminar segments display paired teeth along the margin. Major veins dichotomize to the lamina edge, and finer veins reticulate, forming square to polygonal areoles, with freely ending veinlets. Veins are enclosed by sclerenchymatous sheaths, and the abaxial epidermis is recessed, producing concave areas between veins. Adaxial cuticle is thick, and the epidermis contains rectangular cells with undulating walls. Anomocytic scattered stomata occur on the abaxial surface. Sporangia and trichomes are scattered across the abaxial epidermis in the areolar concavities. Sporangial stalks are short, two to three cells long and four to six cells wide throughout their length. Sporangia have a vertical annulus that is interrupted by the stalk, and they contain trilete spores that correspond to Cibotiumspora jurienensis. Leaf morphology is similar to that of extant Dipteris novoguineensis and fossil Hausmannia spp. A unique combination of characters demonstrates that Hausmannia is a distinct genus of fossil dipterids. An examination of leaves from extant Dipteris rhizomes of various ages suggests that the genus Protorhipis may represent juvenile Hausmannia at some localities. The association of Hausmannia with small pieces of delicate moss gametophytes, fern sporelings, and vegetative remains of Lycopodium and Selaginella at Apple Bay reinforces the interpretation that these fossil dipterids were deposited under storm conditions and that Hausmannia may have grown in disturbed habitats.