Lepidodendron and Sigillaria


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Lepidodendron (lĕp'ĭdōdĕn`drən) and Sigillaria

(sĭjĭlâr`ēə), two principal genera of an extinct group of primitive vascular trees. They dominated the forests of the early Carboniferous periodCarboniferous period
, fifth period of the Paleozoic era of geologic time (see Geologic Timescale, table), from 350 to 290 million years ago. Historical Geology of the Period
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 until the ferns gained ascendancy. Related to the club mossesclub moss,
name generally used for the living species of the class Lycopodiopsida, a primitive subdivision of vascular plants. The Lycopodiopsida were a dominant plant group in the Carboniferous period, when they attained the size of trees, and contributed to the coal deposits
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, they are sometimes called giant club mosses. The spore-bearing leaves formed cones. The tall, thick trunks, rarely branching, were crowned with a cluster of narrow leaves. The closely packed leaf scars left on the stems as the plants grew provide some of the most interesting and common fossils in shales and accompanying coal deposits. In Lepidodendron the leaf scars are diamond-shaped, and in Sigillaria they are arranged in vertical rows. The rhizomes, or root systems, of both genera, known as stigmaria, were thought to be distinct plants when their fossils were first discovered. Actually they served to support the trees and to produce new shoots. Lepidodendron and Sigillaria are classified in the division LycopodiophytaLycopodiophyta
, division of the plant kingdom consisting of the organisms commonly called club mosses and quillworts. As in other vascular plants, the sporophyte, or spore-producing phase, is the conspicuous generation, and the gametophyte, or gamete-producing phase, is minute.
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, order Lepidodendrales.