Anatomically preserved Woodwardia virginica (Blechnaceae) and a new filicalean fern from the middle Miocene Yakima Canyon flora of central Washington, USA

Anatomically preserved Woodwardia virginica (Blechnaceae) and a newly recog nized onocleoid fern are described from the middle Miocene Yakima Canyon fl ora of central Washington State, USA. Identification of the W. virginica fo ssils is based on a combination of vegetative pinnules, rhizome and stipe a natomy, and fertile pinnules with indusiate sori and sporangia Like those o f extant W. virginica. Fronds are isomorphic. Vegetative pinnae are elongat ed and pinnatifid, with a secondary vein paralleling the midvein. Secondary veins of the pinnule lobe anastomose to form primary areoles and are eithe r simple or dicholomize toward the margin. Rhizomes have a simple dictyoste le with 3-5 cauline vascular bundles and often a sclerotic hypodermis. Leaf traces contain two large adaxial vascular bundles that occur laterally and adaxially, flanking an are of 4-6 smaller bundles. Fertile pinnules have l inear sori that are somewhat embedded in the laminae and are enclosed by a thin indusium. Leptosporangia display a vertical annulus and an elongated s talk. A second fern, Wessiea yakimaensis gen. et sp. nov., is represented b y anatomically preserved branching rhizomes and attached frond bases that c onform to the Onoclea-type pattern of rhizome and frond-base vasculature. R hizomes have a simple dictyostele of 4-5 cauline meristeles. Leaf divergenc e is helical, with paired hippocampiform rachial traces. These two ferns oc cur in the same matrix with specimens of Osmunda wehrii. They demonstrate t hat filicalean fern assemblages similar to those of extant temperate floras were well established in western North America by the middle Miocene and f urther emphasize the exceptional species longevity of some homosporous pter idophytes.