Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] is the state tree of Oregon. It is appropriate that the geologically oldest macrofossil record of the genus is also from Oregon; the ~32 Ma Rujada site southeast of Eugene. Revision of the North American impression fossils indicate that only 7 of the 27 (26%) literature citations are correctly assigned to Pseudotsuga. A previously unrecognized specimen from Cartwright Ranch, Idaho is added. These eight occurrences are all within the present geographic range of extant Pseudotsuga in western North America. The genus is known from Miocene and younger horizons of Japan. Records from Europe are considered equivocal. The North American impression fossils can be segregated into three forms on the basis of the size of the ovulate cone and/or winged seed; large, intermediate and small. Based on climatic analyses of the associated dicotyledonous paleofloras, these three forms occurred in three different climatic settings. It is inferred that these occurrences are expressions of ecologically driven evolutionary trends. The earliest record, a large winged seed form near extant P. macrocarpa from the early Oligocene of Oregon, is inferred to be the least derived Pseudotsuga. It was adapted to a mean annual temperature centered on ~13 C, an intermediate mean annual range of temperature centered on ~22 C, with ~150 cm precipitation distributed through a seven plus month growing season; this condition is typical for the bulk of the least modified species of extant Northern Hemisphere conifers. Through time, Pseudotsuga adapted to dryer, and both cooler or warmer, climates. The large seed form adapted to dryer-warmer. An intermediate-sized form from the late middle Miocene was dryer-cooler. The small-sized P. menziesii type is known from the middle Miocene on in dryer, but both cooler and warmer settings. The history of Pseudotsuga viewed in the present framework demonstrates a dynamic adaptive history.

Key words: diversification, Douglas-fir, history, paleoecology, Pseudotsuga