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Journal Article

Lyssoxylon grigsbyi, a Cycad Trunk from the Upper Triassic of Arizona and New Mexico

R. E. Gould
American Journal of Botany
Vol. 58, No. 3 (Mar., 1971), pp. 239-248
Stable URL: http://www.jstor.org/stable/2441159
Page Count: 10
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Lyssoxylon grigsbyi, a Cycad Trunk from the Upper Triassic of Arizona and New Mexico
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Abstract

Lyssoxylon grigsbyi Daugherty, a petrified stem with petiole bases, was originally described from the Upper Triassic Chinle Formation of Arizona and considered to be a member of the Williamsoniaceae. Investigation of additional material from a similar horizon in New Mexico, together with re-examination of preparations of the holotype, suggest that the plant, with its monoxylic stele, girdling leaf traces, and bicelled epidermal hairs is a true cycad. Cells of the New Mexico specimens contain structures interpreted as preserved nuclei.

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