Crepet, W. L. and C. P. Daghlian. 1982. Euphorbioid inflorescences from the Middle Eocene Claiborne Formation. American Journal of Botany 69 (2): 258-266.

Abstract: Inflorescences from the Claiborne Formation of western Tennessee are remarkably similar to those of the tribe Hippomaneae, subfamily Euphorbioideae, of the Euphorbiaceae. The fossil inflorescences are spikes of bract-subtended cymules of at least three florets each. Florets are composed of at least three stamens. Palynological features of the fossils are also shared by the Hippomaneae. Fossil pollen is tricolporate, prolate (26.9 x 20.6 µm; P/E = 1.3), with lalongate pores. Exine structure is tectate columellate with a perforate tectum. The exine is reticulate and the muri are conspicuously striate. these specimens represent the first fossil floral evidence of the Euphorbiaceae. It is surprising that inflorescences of the Hippomaneae so modern in aspect existed in the Middle Eocene, since the tribe is universally considered to be one of the most advanced in the family.

FOSSIL PHOTOS

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Hippomaneoidea warmanensis
Actual width in ( ) unless otherwise noted.

Inflorescence
(length= 1.8 cm)
Florets
(length= 6.5 mm)
Pollen grain
(grain length= 28 µm)
Transmision electron microscope
view of pollen grain
(13 µm)