| 词条 | Yunia |
| 释义 |
| fossil_range = {{Geological range/linked|Early Devonian}} | image = Yunia dichotoma reconstruccion.jpg | image_upright = 0.7 | image_caption = Reconstruction of Yunia dichotoma according to its description. | taxon = Yunia | authority = S.G.Hao & C.B.Beck (1991)[1] | subdivision_ranks = Species | subdivision = †Y. dichotoma S.G.Hao & C.B.Beck (1991) }}Yunia is a genus of extinct vascular plants from the Early Devonian (Pragian or Siegenian stage, around {{Period span/brief|Pragian}}). It was first described from the Posongchong Formation of Yunnan, China. The leafless plant consisted of spiny stems, some 2 to 5 cm wide, which branched dichotomously at wide angles in a cruciate arrangement. Each stem contained vascular tissue with one or two strands of protoxylem. The spore-forming organs (sporangia) were elongated and borne on short stalks. The spores had a relatively smooth sculptural pattern and were trilete (i.e. each spore has three lines on it resulting from its formation in a tetrahedral set of four spores).[1][2] In 2004, Crane et al. published a simplified cladogram for the polysporangiophytes in which Yunia is basal to the lycophytes (clubmosses and relatives).[3] It had previously been placed in the "trimerophytes"[1] (a group now thought to be paraphyletic), which were considered to have given rise to all the other vascular plants except the lycophytes.[4] {{clade| label1=tracheophytes | 1={{Clade tracheophyte|lycophytes=collapsed|euphyllophytes=collapsed}} }} References1. ^1 2 {{Citation |last=Hao |first=Shou-Gang |last2=Beck |first2=Charles B. |year=1991 |title=Yunia dichotoma, a Lower Devonian plant from Yunnan, China |journal=Review of Palaeobotany and Palynology |volume=68 |issue=3-4 |pages=181–195 |doi=10.1016/0034-6667(91)90022-U |lastauthoramp=yes |url=https://deepblue.lib.umich.edu/bitstream/2027.42/29227/1/0000282.pdf }} 2. ^{{Citation |last=Taylor |first=T.N. |last2=Taylor |first2=E.L. |last3=Krings |first3=M. |year=2009 |title=Paleobotany : The Biology and Evolution of Fossil Plants |edition=2nd |publication-place=Amsterdam; Boston |publisher=Academic Press |isbn=978-0-12-373972-8 |lastauthoramp=yes }}, p. 262 3. ^{{Citation |last=Crane |first=P.R. |last2=Herendeen |first2=P. |last3=Friis |first3=E.M. |year=2004 |title=Fossils and plant phylogeny |journal=American Journal of Botany |volume=91 |pages=1683–99 |url=http://www.amjbot.org/cgi/content/full/91/10/1683 |accessdate=2011-01-27 |doi=10.3732/ajb.91.10.1683 |issue=10 |pmid=21652317}} 4. ^{{Harvnb|Taylor|Taylor|Krings|2009|p=259ff.}} External links
1 : Early Devonian plants |
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