Lygodium Foliage with Intact Sorophores from the Eocene of Wyoming

Abstract

Specimens of Lygodium kaulfussi with attached sorophores and in situ spores from the late Eocene Bridger Formation of Woming are described and compared with similar fossil remains from the early Tertiary of other areas in North America, Europe, South America, and Australia. On the basis of the same criteria emphasized in the taxonomy of extant Lygodium species, the Eocene material from Europe and North America represents a single wide-ranging species that was distinct in some features from the Eocene species known from the Southern Hemisphere. Although not identical with any modern species, L. kaulfussi closely resembles extant L. palmatum of eastern North America in having highly dissected nonlaminar fertile pinnae and psilate spores. Strong dimorphism between the sterile and fertile foliage, as occurs in L. kaulfussi and L. palmatum, was widespread in both the Nothern and Southern Hemispheres in the Eocene and predates the Neogene appearance of the weakly dimorphic foliage characteristic of most extant Lygodium species.