Cycadeoidophyta

Cycadeoidophyta

▪ gymnosperm division
also called  Bennettitophyta 

      an extinct division of plants with certain features in common with cycads (division Pinophyta) and grouped with them and the seed ferns (division Pteridospermophyta). Both the cycadeoids and the cycads dominated the vegetation in the Jurassic Period (about 200 to 145 million years ago)—called the “Age of Cycads”—and both are presumed to have originated from a seed-fern ancestor. The evolution of cycadeoids seems to have paralleled the rise and fall of the dinosaurs. Unlike the cycads, in which a few large strobili (conelike reproductive bodies) are borne at the stem tip, the cycadeoids produced many smaller strobili in rosettes among the leaf bases.

      The Cycadeoidophyta contained two important families: Williamsoniaceae and Cycadeoidaceae (Bennettitaceae). Williamsonia, the best-known genus of its family, had a columnar trunk with frondlike leaves at branch tips; its fossil cones are not well defined. Williamsoniella, a related genus, was shrubby; fossil leaves placed in the genus Nilssoniopteris are believed to belong here. Cycadeoidea (Bennettites) had a barrel-shaped trunk, like a large pineapple, with a crown of leaves; its cones are reconstructed in detail from fossils. Monanthesia is the genus name reserved for fossil cycadeoid trunks with cones in the leaf axils.

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Universalium. 2010.

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  • gymnosperm — gymnospermism, n. /jim neuh sperrm /, n. Bot. a vascular plant having seeds that are not enclosed in an ovary; a conifer or cycad. Cf. angiosperm. [1820 30; < NL gymnospermae name of type. See GYMNO , SPERM] * * * Any woody plant that reproduces… …   Universalium

  • cycadeoid — noun Etymology: New Latin Cycadeoidales, group name, ultimately from Cycad , Cycas Date: 1860 any of a division (Cycadeoidophyta syn. Bennettitophyta) of extinct Jurassic to Cretaceous gymnosperms that differ from the cycadophytes chiefly in… …   New Collegiate Dictionary

  • angiosperm — /an jee euh sperrm /, n. Bot. a plant having its seeds enclosed in an ovary; a flowering plant. Cf. gymnosperm. [ANGIO + SPERM] * * * ▪ plant Introduction       any member of the more than 300,000 species of flowering plants (division Anthophyta) …   Universalium

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  • Jurassic Period — Interval of geologic time, 206–144 million years ago, that is one of the three major divisions of the Mesozoic Era, preceded by the Triassic Period and followed by the Cretaceous. During the Jurassic, Pangea began to break up into the present day …   Universalium

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