Abstract
A large collection (49 specimens) of early Eocene Fraxinus (ash) samaras enabled us to evaluate whether or not more than one species was present at the Quilchena fossil site. Analysis of living ashes indicates that morphology of the samara tips is sometimes cited as a taxonomic criterion, and sometimes assumed to be due to intraspecific variation. Two shale slabs with multiple samaras, some still attached to their fruiting panicle, have been recovered, and in each case all samaras were either emarginate at the tip, or entire, indicating a degree of fidelity of tip type, and the possibility that more than one species may be represented. Analysis of 27 dispersed samaras with notched tips, involving measurements of overall length, width, venation, and seed morphology, reveal differences with unnotched samaras from the same site, with width significantly greater (p < 0.05) for the notched samaras. Together with other differences that are not statistically significant, the larger size for notched specimens encouraged us to describe a new species, Fraxinus eoemarginata sp. nov. Quilchena is well dated to the early Eocene at 51.5 million years, making it the oldest radiometrically documented site for diversification of Fraxinus species.
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