''Yunia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of extinct

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...

s from the

Early Devonian The Early Devonian is the first of three Epoch (geology), epochs comprising the Devonian period, corresponding to the Lower Devonian Series (stratigraphy), series. It lasted from and began with the Lochkovian Stage , which was followed by the P ...

(Pragian or Siegenian stage, around ). It was first described from the Posongchong Formation of

Yunnan Yunnan , () is a landlocked Provinces of China, province in Southwest China, the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is ...

, 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 Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There ...

with one or two strands of

protoxylem Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...

. The spore-forming organs (

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

) 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). In 2004, Crane et al. published a simplified

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

for the

polysporangiophyte Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that bear sporangia. The name literally means 'many sporangia plant'. The cl ...

s in which ''Yunia'' is basal to the

lycophytes The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest ...

(clubmosses and relatives). It had previously been placed in the "

trimerophyte Trimerophytopsida (or Trimeropsida) is a class of early vascular plants from the Devonian, informally called trimerophytes. It contains genera such as ''Psilophyton''. This group is probably paraphyletic, and is believed to be the ancestral group ...

s" (a group now thought to be paraphyletic), which were considered to have given rise to all the other vascular plants ''except'' the lycophytes. Hao and Xue in 2013 considered the genus as a questionable zosterophyll.

References

External links

Cladogram
from {{Taxonbar, from=Q8061285 Early Devonian plants Zosterophylls Prehistoric lycophyte genera