Crepet, W. L. and K. C. Nixon. 1989. Earliest megafossil evidence of Fagaceae: phylogenetic and biogeographic implications. American Journal of Botany 76 (6): 842-855.

Abstract: Fossil evidence of Fagaceae from the Paleocene/Eocene boundary of western Tennessee is described and discussed. These fossils include a newly discovered pistillate inflorescence and dispersed fruits of subfamily Castaneoideae as well as a taxon that resembles modern trigonobalanoids (pistillate inflorescences and dispersed mature fruits). Fossil staminate catkins with fagaceous pollen, which we suggest may be conspecific with the trigonobalanoid infructescences, are also found at the locality. Two distinct types of fagaceous leaves are present at the locality. The reproductive structures are the oldest megafossils unequivocally assignable to Fagaceae and Castaneoideae. In addition, the fossils provide insights into the chronology of diversification, biogeography, and phylogeny of Fagaceae. The trigonobalanoid remains may also provide insights into the timing and circumstances of the evolution of wind pollination in Fagaceae.

FOSSIL PHOTOS

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Castanopsoidea, Trigonobalanoidea, Paleojulacea
Actual width in ( ) unless otherwise noted.

Castanopsoidea columbiana
infructescence
(1.2 cm)
Closer view of immature fruits
(image= 5.4 mm)
Ripe cupule of
Castanopsoidea columbiana
(2.2 cm)

Pollen grain of
Castanopsoidea columbiana
(grain length= 16 µm)
Paleojulacea laxa,
mature catkin
(length= 3.3 cm)
Unexpanded catkin
(length= 9 mm)

Pollen grain of
Paleojulacea laxa
(15 µm)
Trigonobalanoidea americana
inflorescence
(length= 5.6 cm)

Mature fruit of
Trigonobalanoidea americana
(6.3 mm)
Three fruits in a cupule
(1.1 cm)