A filmy fern from the upper triassic of North Carolina (USA)

Modern cladistic analyses support earlier suggestions that the Hymenophylla ceae (the "filmy ferns") are basal filicaleans. However, the fossil record of the family is ambiguous. A new fossil fern, Hopetedia praetermissa gen. et sp. nov., from the Upper Triassic Pekin Formation of North Carolina (USA ), is described and interpreted as the oldest unequivocal representative of the Hymenophyllaceae based primarily on general frond morphology, indirect evidence for a filmy (membranaceous) habit, and soral position and morphol ogy. Particularly compelling as evidence for the hymenophyllaceous affinity of H. praetermissa is the funneliform structure of the indusium (involucre ), which is similar to that found primarilly in the extant Trichomanes (sen su lato) clade. However, the receptacle in H. praetermissa is relatively sh ort and, thus, more like most representatives of the Hymenophyllum (sensu l ato) clade. The Triassic age of this fossil is consistent with the basal or near basal position of the Hymenophyllaceae in all recent phylogenetic ana lyses of the filicalean ferns. Hopetedia preatermissa is evaluated in relat ionship to several previous reports of fossil Hymenophyllaceae.