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Discalis
''Discalis'' is a genus of extinct vascular plants of the Early Devonian (Pragian or Siegenian stage, around ). The name is derived from the Greek , referring to the disc-shaped sporangia (spore-forming organs). The genus was first described by Hao in 1989 based on fossil specimens from the Posongchong Formation, Wenshan district, Yunnan, China.
==Description==
The leafless sporophyte of ''D. longistipa'' consisted of creeping stems (axes) up to in diameter with many K- or H-shaped branches as well as upturned or trailing stems, slightly smaller in diameter, which also branched. All stems had irregularly arranged multicellular spines up to long with expanded tips. The stems which did not bear sporangia had coiled (circinnate) tips. Fertile stems bore disc-shaped sporangia laterally on stalks up to 5 mm long, forming open spikes. The sporangia, which were about in diameter, had spines like the stems, and split (dehisced) along their margin to release the trilete spores, which were in diameter. Vascular tissue was present in the stems, with tracheids having annular, spiral thickenings.〔〔, p. 254〕
''D. longistipa'' somewhat resembles ''Sawdonia'', but differs in branching pattern and in the arrangement of the sporangia, including their long stalks.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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