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Premise of research. Newly recognized compression fossils of fertile leptosporangiate ferns assignable to Dennstaedtia Bernh. (Dennstaedtiaceae) and Hymenophyllum Sm. (Hymenophyllaceae) are described from the latest early Eocene floras of the Okanogan Highlands, British Columbia, Canada, and northeastern Washington. Methodology. Specimens were photographed with reflected light microscopy and were studied morphologically in comparison with related fossil and extant forms. Focus-shift stacking was used to layer photos of some specimens. Some were photographed with polarized light. The holotype specimen of Dennstaedtia christophelii sp. nov. was also studied with environmental scanning electron microscopy. Pivotal results. We describe D. christophelii sp. nov. (Dennstaedtiaceae) and Hymenophyllum axsmithii sp. nov. (Hymenophyllaceae) on the basis of vegetative and fertile remains of fragmentary fronds. Specimens of D. christophelii are one-pinnate-pinnatifid to bipinnate and bear frequent marginal round sori in cuplike indusia on small crenulate to dissected pinnae. Sporangia each have a prominent annulus with approximately six to eight long cells visible. Hymenophyllum axsmithii has the type of lamina cutting, sorus position, alate rachis, sorus shape, and venation corresponding to Hymenophyllum , subgenus Sphaerocionium (Hymenophyllaceae). The numerous sporangia per sori each bear a prominent annulus, and 7–10 casts of spores are noted in some sporangia. Conclusions. These fossils document the occurrence of leptosporangiate fern diversity in the early Eocene Okanogan Highlands floras. Dennstaedtia christophelii represents one of several occurrences of Dennstaedtiaceae in the Eocene. Hymenophyllum axsmithii is the first unequivocal member of Hymenophyllaceae to be reported from these diverse plant and insect assemblages from lacustrine and swamp settings under warm temperate climates of the latest early Eocene. [ABSTRACT FROM AUTHOR]

Premise: Paleontologists use tooth form to assess diets of fossil mammals. Plants would also be expected to adapt their morphology to respond to herbivory. Fossil nettle leaves with definitive stinging trichomes (tribe Urticeae, family Urticaceae) are described from the early Eocene upland lacustrine floras of the Okanogan Highlands, British Columbia, Canada. This is the first report of stinging trichomes in the fossil record. Their occurrence in western North America at a time of major large herbivorous mammal radiation suggests they acted, as they do today, as a deterrent for mammal herbivory. Methods: Fossil leaf compressions and extant leaves were photographed with standard methods. Focus‐shift stacking was used to layer photos of the fossil leaves. Results: Urticaceous fossil leaves from the Okanogan Highlands greatly resemble their modern relatives in leaf morphology and particularly in both stinging and nonstinging trichomes. Nettles are common components of the flora of the Volcanoes National Park in Rwanda. This region is used as a modern analogue for the Okanogan Highlands, based on comparable elevation, equable conditions that host both similar floras and large folivores. Conclusions: Nettles in tribe Urticeae (Urticaceae) producing leaves with stinging and nonstinging trichomes were already present in the early Eocene of western North America at a pivotal time during the early radiation of modern mammalian herbivore groups. They offer tantalizing evidence of a selective response that plants may have developed to protect themselves from the evolving mammalian herbivores of that time. [ABSTRACT FROM AUTHOR]

The history of plant fossil collecting in the Okanagan (Okanogan) Highlands of British Columbia and northeastern Washington is closely intertwined with the history of geological surveys and mining activities from the 1870s onward. The first descriptions of fossil plants from British Columbia were published in 1870-1920 by J.W. Dawson, G.M. Dawson, and D.P. Penhallow. In the United States, fossil leaves and fish were first recognized at Republic, Washington, by miners in the early 1900s. Many early workers considered these floras to be of Oligocene or Miocene age. C.A. Arnold described Canadian occurrences of conifers and Azolla in the 1950s. Palynological studies in the 1960s by L.V. Hills, G.E. Rouse, and others and those of fossil fish by M.V.H. Wilson in the 1970-1980s provided the framework for paleobotanical research at several key localities. Permineralized plants were first described from the Princeton chert in the 1970s by C.N. Miller, J.F. Basinger, and others, followed by R.A. Stockey and her students. W.C. Wehr and K.R. Johnson revitalized the study of fossils at Republic with the discovery of a diverse assemblage in 1977. In 1987, J.A. Wolfe and Wehr produced a United States Geological Survey monograph on Republic, and Wehr cofounded the Stonerose Interpretive Center as a venue for public collecting. Systematic studies of the Okanagan Highlands plants, as well as paleoecological and paleoclimate reconstructions from palynomorphs and leaf floras, continue to expand our understanding of this important Early Eocene assemblage. [ABSTRACT FROM AUTHOR]

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A distinctive, extinct type of flower and fruit is described based on coalified compression and impression fossils from the Eocene lake bed deposits of McAbee, British Columbia. Dillhoffia cachensis gen. et sp. nov. has an elongate-ellipsoidal fruit with an epigynous, completely connate funnelform calyx 1.8–2.9 cm in diameter, with an unlobed, orbicular margin. The fruit narrows apically into a single style divided into four slightly recurved stigmatic arms. Fruits are pedicellate, borne in globose heads. Stamens, pollen, and internal fruit morphology remain unknown, but the available details of gynoecial and perianth morphology present a suite of characters not encountered in any known extant genus, and the familial affinities remain uncertain. This is noteworthy, because many other elements of the same Eocene flora represent extant genera with clear familial assignments such as Cunninghamia, Ginkgo, Aesculus, Alnus, Betula, Dipteronia, Fagus, Trochodendron, and Ulmus. [ABSTRACT FROM AUTHOR]