Huia (plant)
Encyclopedia
Huia is a genus of extinct vascular plant
s of the Early Devonian (Pragian or Siegenian, around ). The genus was first described in 1985 based on fossil specimens from the Posongchong Formation, Wenshan district
, Yunnan, China.
of H. recurvata consisted of leafless stems (axes), branching both dichotomously and pseudomonopodially (i.e. with unequal divisions creating a 'main stem'). The sporangia
(spore-forming organs) were born in terminal spikes on fertile stems, with the sporangia spirally arranged on stalks which curved downwards. The central strand of vascular tissue
contained G-type tracheid
s. It was initially provisionally assigned to the "rhyniophytes". However, this group is defined as having terminal sporangia, whereas those of Huia are lateral, suggesting affinity with the zosterophylls.
A second species, H. gracilis, was described from the Xujiachong Formation (Pragian–early Emsian), Qujing
district, Yunnan, China. It differs from H. recurvata in its more slender morphology and its lack of pseudomonopodial branching. The adaxial sporangia, which were oval or elongated oval in shape, split (dehisced) along their length at right angles to the stem. It is suggested that Huia may have originated from early Cooksonia
-like plants. Others suggest that its position is uncertain.
(living and extinct clubmosses and relatives).
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s of the Early Devonian (Pragian or Siegenian, around ). The genus was first described in 1985 based on fossil specimens from the Posongchong Formation, Wenshan district
Wenshan Zhuang and Miao Autonomous Prefecture
Wenshan Zhuang and Miao Autonomous Prefecture is an autonomous prefecture in Yunnan Province, China.-Subdivisions:-Ethnic groups:Wenshan is highly diverse...
, Yunnan, China.
Description
The sporophyteSporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or algae that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants...
of H. recurvata consisted of leafless stems (axes), branching both dichotomously and pseudomonopodially (i.e. with unequal divisions creating a 'main stem'). The sporangia
Sporangium
A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...
(spore-forming organs) were born in terminal spikes on fertile stems, with the sporangia spirally arranged on stalks which curved downwards. The central strand of vascular tissue
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 are also two meristems associated with vascular tissue:...
contained G-type tracheid
Tracheid
Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. Tracheids are one of two types of tracheary elements, vessel elements being the other. All tracheary elements develop a thick lignified cell wall, and at maturity the protoplast...
s. It was initially provisionally assigned to the "rhyniophytes". However, this group is defined as having terminal sporangia, whereas those of Huia are lateral, suggesting affinity with the zosterophylls.
A second species, H. gracilis, was described from the Xujiachong Formation (Pragian–early Emsian), Qujing
Qujing
Qujing is a prefecture-level city in eastern Yunnan province of Southwest China. It is an important industrial city, and is Yunnan's second largest city by population, after Kunming....
district, Yunnan, China. It differs from H. recurvata in its more slender morphology and its lack of pseudomonopodial branching. The adaxial sporangia, which were oval or elongated oval in shape, split (dehisced) along their length at right angles to the stem. It is suggested that Huia may have originated from early Cooksonia
Cooksonia
Cooksonia is an extinct grouping of primitive land plants. The earliest Cooksonia date from the middle of the Silurian ; the group continues to be an important component of the flora until the Early Devonian, a total time span of...
-like plants. Others suggest that its position is uncertain.
Phylogeny
A cladogram published in 2004 by Crane et al. places Huia in a paraphyletic stem group of broadly defined "zosterophylls", basal to the lycopsidsLycopodiophyta
The Division Lycopodiophyta is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant vascular plant division at around 410 million years old, and includes some of the most "primitive" extant species...
(living and extinct clubmosses and relatives).
External links
- Cladogram from
