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A new genus is described based on fossilized winged fruits from former lake deposits of Wyoming, Utah, Colorado, Oregon, and British Columbia, ranging in age from latest Paleocene to early Middle Eocene. Lagokarpos lacustris McMurran et Manchester gen. et sp. nov. fruits have an elliptical to globose seed body and a conspicuous pair of apical wings with pinnate venation. These windâ€ï¿½dispersed fruits are compared with and distinguished from similar extant winged fruits such as Dipterocarpus Gaertn f. (Dipterocarpaceae), Gyrocarpus Jacq. (Hernandiaceae), and Alberta E. Meyer (Rubiaceae). No modern fruit was found to exhibit the combination of characters seen in Lagokarpos, and we conclude that it represents an extinct...
A new genus is described based on fossilized winged fruits from former lake deposits of Wyoming, Utah, Colorado, Oregon, and British Columbia, ranging in age from latest Paleocene to early Middle Eocene. Lagokarpos lacustris McMurran et Manchester gen. et sp. nov. fruits have an elliptical to globose seed body and a conspicuous pair of apical wings with pinnate venation. These wind?dispersed fruits are compared with and distinguished from similar extant winged fruits such as Dipterocarpus Gaertn f. (Dipterocarpaceae), Gyrocarpus Jacq. (Hernandiaceae), and Alberta E. Meyer (Rubiaceae). No modern fruit was found to exhibit the combination of characters seen in Lagokarpos, and we conclude that it represents an extinct...
New paleomagnetic and stable isotopic results from the northeastern margin of the greater Green River Basin (South Pass, Wyoming) provide a refined geochronological context for the Wasatchian/Bridgerian Land Mammal Age boundary and suggest the existence of large amplitude Milankovich-scale carbon and oxygen isotopic oscillations in this area during the early Eocene. Analysis of 55 paleomagnetic sites through a 310 m section of Wasatch, Green River, and Bridger Formations indicates several reversals that can be correlated to the Geomagnetic Polarity Time Scale using radiometric age constraints. This correlation places the Wasatchian/Bridgerian boundary in Chron C23r at about 52 Ma, approximately two million years...
This study is the first to employ spectral analysis to examine meter-scale sedimentary cyclicity in the Wilkins Peak Member of the lower Eocene Green River Formation of Wyoming. Generally regarded as the classic example for orbital forcing of lacustrine sediments at eccentricity and precession time scales, this long-standing interpretation was recently contested, with a much shorter duration (≤ 10 ky) inferred for the dominant cyclicity. Earlier work lacked adequate age control or spectral analysis or both. Our analysis is based upon an evaluation in the frequency domain of oil-yield values from four boreholes, accuracy estimation for suggested orbital interpretations, and comparison to independent geochronology....
An extinct genus of the Polemoniaceae is described from one complete fossil plant preserved in shale of the Eocene Green River Formation, Utah. Combined vegetative and reproductive characters including the taproot, basal and cauline pinnatifid leaves, primary peduncular leaves, secondary peduncular bracts, pedicel bracts, fruits in groups of three, and persistent calyx, support placement of this plant close to the extant genus Gilia. Gilisenium hueberi gen. et sp. nov. represents a rare record of an herbaceous plant, and the oldest megafossil for the family Polemoniaceae. Published in Review of Palaeobotany and Palynology, volume 104, issue 1, on pages 39 - 49, in 1998.