Anatomically preserved taxodiaceous ovulate cones, isolated cone scales, and seeds, some containing embryos, are described from the middle Miocene Yakima Canyon flora of central Washington State, USA. These remains are associated with Osmunda, Woodwardia, Liquidambar and Nyssa, taxa characteristic of modern-day Taxodium swamps of coastal southeastern North America. Cones are 13 mm x 7 mm across and are characterized by a narrow cone axis surrounded by helically arranged cone scales bearing two ovules each. Cone scales are 11-12 mm wide x 9-11 mm long x 4 mm thick and four-sided with two depressions on their inner surface where seeds were borne. The cone scales have prominent teeth on the apical margin and a lateral umbo projecting 3 mm out from the face of the scale. Winged, elongate seeds are 11.5-13 mm long x 6 mm wide x 3-4 mm high, and triangular in cross section. The seed integument has three layers: an outer layer 3-5 cells thick of small cuboidial cells with dark contents, a wide central region of larger isodiametric to radially elongate cells that extends laterally to form the wings, and an inner layer comprised of 2-3 flattened thin-walled radially elongate cells. Some specimens have a layer of large, dark palisade cells inside the integument that is interpreted as the nucellus, but this layer is variably preserved. The megaspore membrane appears as a thin line outside the megagametophyte tissue, which contains cells filled with contents, possibly starch. Several specimens contain mature embryos with well developed radicles and cotyledons. Because most of the Yakima fossils are of isolated cone scales and seeds, with relatively few intact cones occurring, we believe that they were deciduous, falling apart at maturity as occurs in modern-day Taxodium.

Key words: Miocene, ovulate cone, permineralization, taxodiaceous conifers, Taxodium, Yakima Canyon