TIFFNEY, BRUCE H.* AND NORMAN WANG. Geological Sciences and College of Creative Studies, University of California, Santa Barbara, CA 93106. - Seeds of Rhododendron from the Eocene of California.
Rhododendron is known from seeds in the Paleocene of England.
All other reports, including those from North America, are based on
fossil leaves, many of poor quality. In addition, the foliar
characters of fossil Rhododendron may mimic those of the leaves
of several genera of Fagaceae, requiring great care in identification.
Thus, pre-existing reports of Tertiary age North American
Rhododendron require verification. We report seeds clearly
assignable to Rhododendron from the La Porte Flora of Northern
California. This flora has been dated by whole rock
238U/205Pb methods at 33.2 Ma (corrected),
placing it in the Early Oligocene, but the climatic affinities of the
flora suggest that it is pre-deterioration and thus likely of Late
Eocene age. Thus, Rhododendron had achieved at least a
Euramerican distribution by the Eocene. Rhododendron seeds
fall into three morphological categories which bear some association
with the higher order systematic divisions of the genus. Our
investigation suggests that the variability of seed morphology is such
that identification to lower taxonomic groupings is not possible.
Key words: California, Eocene, Ericaceae, fossil, Rhododendron, seed