Crepet, W. L. and C. P. Daghlian. 1980. Castaneoid inflorescences from the Middle Eocene of Tennessee and the diagnostic value of pollen (at the subfamily level) in the Fagaceae. American Journal of Botany 67 (5): 739-757.

Abstract: In order to help evaluate affinities of four types of inflorescences that shared gross pollen and inflorescence morphology with extant Fagaceae, the pollen of the extant Fagaceae was analyzed with light, scanning, and in some cases transmission electron microscopy. The survey illustrates the range of pollen structure in the Fagaceae and confirms that exine ornamentation is a good diagnostic character for determining subfamilies within the modern Fagaceae. Careful comparison of the pollen and floral morphology of the fossil with similar features of the extant Fagaceae revealed only one of these fossil inflorescences was fagoid (the other inflorescences will be considered in a subsequent manuscript). The fagaceous inflorescences are catkins conforming in all aspects of pollen, inflorescence, and floret morphology with catkins of the modern subfamily Castaneoideae. The fossil catkins also share the robust inflorescence axis with modern castaneoid inflorescences suggesting that they, too, may have been upright and insect pollinated. The nature of these fossils is consistent with observations that several other families of the "Amentiferae" evolved rapidly during the Upper Cretaceous-Middle Eocene and this trend suggests that conditions favoring wind pollinated arborescent angiosperm species were optimal during that interval.

FOSSIL PHOTOS

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Castaneoidea puryearensis
Actual width in ( ) unless otherwise noted.

Castaneoidea inflorescence
(length= 3.8 cm)
Closer view of several florets
(image= 5 mm)
Anther filled with pollen
(185 µm)

Pollen grain
(grain length= 12 µm)
Pollen grain surface
(image= 6 µm)