Yunia

Yunia is a genus of extinct vascular plants from the Early Devonian (Pragian or Siegenian stage, around 411 to 408 million years ago). 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]

Yunia
Temporal range: Early Devonian
Reconstruction of Yunia dichotoma according to its description.
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Lycophytes
Plesion: †Zosterophylls (?)
Genus: †Yunia
S.G.Hao & C.B.Beck (1991)[1]
Species

†Y. dichotoma S.G.Hao & C.B.Beck (1991)

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]

tracheophytes
 

† Rhyniaceae (Huvenia, Rhynia, Stockmansella)

 
 
 

† basal groups (Aberlemnia caledonica [=Cooksonia caledonica], Cooksonia pertoni)

 
 
 

† basal groups (Cooksonia cambrensis, Renalia, Sartilmania, Uskiella, Yunia)

 
 

lycophytes

 
 
 

euphyllophytes

 
 
 

Hao and Xue in 2013 considered the genus as a questionable zosterophyll.[5]

References
  1. Hao, Shou-Gang & Beck, Charles B. (1991), "Yunia dichotoma, a Lower Devonian plant from Yunnan, China" (PDF), Review of Palaeobotany and Palynology, 68 (3–4): 181–195, doi:10.1016/0034-6667(91)90022-U, hdl:2027.42/29227
  2. Taylor, T.N.; Taylor, E.L. & Krings, M. (2009), Paleobotany : The Biology and Evolution of Fossil Plants (2nd ed.), Amsterdam; Boston: Academic Press, ISBN 978-0-12-373972-8, p. 262
  3. Crane, P.R.; Herendeen, P.; Friis, E.M. (2004), "Fossils and plant phylogeny", American Journal of Botany, 91 (10): 1683–99, doi:10.3732/ajb.91.10.1683, PMID 21652317, retrieved 2011-01-27
  4. Taylor, Taylor & Krings 2009, p. 259ff.
  5. Hao, Shougang & Xue, Jinzhuang (2013), The early Devonian Posongchong flora of Yunnan: a contribution to an understanding of the evolution and early diversification of vascular plants, Beijing: Science Press, p. 52, ISBN 978-7-03-036616-0, retrieved 2019-10-25
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