| Huia Temporal range: | |
|---|---|
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Lycophytes (?) |
| Genus: | † Huia Geng [1] |
| Species | |
Huia is a genus of extinct vascular plants of the Early Devonian (Pragian or Siegenian, around 410 million years ago). The genus was first described in 1985 based on fossil specimens from the Posongchong Formation, Wenshan district, Yunnan, China. [1] [3]
The sporophyte 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 tracheids. It was initially provisionally assigned to the "rhyniophytes". [1] However, this group is defined as having terminal sporangia, whereas those of Huia are lateral, suggesting affinity with the zosterophylls. [3] The Huia plant may show traits of being similar to Lycophytina but has ovate reflexed sporangia which are long stalked and dehisce longitudinally while being vascular, making it more like a vascular plant (tracheophyte). [2]
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. [2] Others suggest that its position is uncertain. [4]
A cladogram published in 2004 by Crane et al. places Huia in a paraphyletic stem group of broadly defined "zosterophylls", basal to the lycopsids (living and extinct clubmosses and relatives). [3]
| lycophytes |
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By contrast, Hao and Xue in 2013 listed the genus as a rhyniophyte, thus placing it outside the zosterophylls and even lycophytes. [5]
The rhyniophytes are a group of extinct early vascular plants that are considered to be similar to the genus Rhynia, found in the Early Devonian. Sources vary in the name and rank used for this group, some treating it as the class Rhyniopsida, others as the subdivision Rhyniophytina or the division Rhyniophyta. The first definition of the group, under the name Rhyniophytina, was by Banks, since when there have been many redefinitions, including by Banks himself. "As a result, the Rhyniophytina have slowly dissolved into a heterogeneous collection of plants ... the group contains only one species on which all authors agree: the type species Rhynia gwynne-vaughanii". When defined very broadly, the group consists of plants with dichotomously branched, naked aerial axes ("stems") with terminal spore-bearing structures (sporangia). The rhyniophytes are considered to be stem group tracheophytes.
Zosterophyllum was a genus of Silurian-Devonian vascular land plants with naked branching axes on which usually kidney-shaped sporangia were arranged in lateral positions. It is the type genus for the group known as zosterophylls, thought to be part of the lineage from which modern lycophytes evolved. More than 20 species have been described.
Crenaticaulis was an early genus of slender, dichotomously branching, leafless land plants, known from the Devonian period and first described in 1969. They were probably allied to the zosterophylls, and are assigned to subdivision Zosterophyllophytina, or class Zosterophyllopsida. They bore branches and scalariform tracheids.
The Horneophytopsida, informally called horneophytes, are a class of extinct plants which consisted of branched stems without leaves, true roots or vascular tissue, found from the Late Silurian to the Early Devonian. They are the simplest known polysporangiophytes, i.e. plants with sporophytes bearing many spore-forming organs (sporangia) on branched stems. They were formerly classified among the rhyniophytes, but it was later found that some of the original members of the group had simple vascular tissue and others did not. The group has also been treated as the division Horneophyta.
Yunia is a genus of extinct vascular plants from the Early Devonian. 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.
Hicklingia is a genus of extinct plants of the Middle Devonian. Compressed specimens were first described in 1923 from the Old Red Sandstone of Scotland. Initially the genus was placed in the "rhyniophytes", but this group is defined as having terminal sporangia, and later work showed that the sporangia of Hicklingia were lateral rather than strictly terminal, so that it is now regarded as having affinities with the zosterophylls.
Gumuia is a genus of extinct vascular plants of the Early Devonian. The genus was first described in 1989 based on fossil specimens from the Posongchong Formation, Wenshan district, Yunnan, China.
Adoketophyton is a genus of extinct vascular plants of the Early Devonian. The plant was first described in 1977 based on fossil specimens from the Posongchong Formation, Wenshan district, Yunnan, China. These were originally named Zosterophyllum subverticillatum; later the species was transferred to a new genus as Adoketophyton subverticillatum. One cladistic analysis suggested that it is a lycophyte, related to the zosterophylls. Other researchers regard its placement within the vascular plants as uncertain.
Discalis is a genus of extinct vascular plants of the Early Devonian. The name is derived from the Greek δίσκος, referring to the disc-shaped sporangia. The genus was first described by Hao in 1989 based on fossil specimens from the Posongchong Formation, Wenshan district, Yunnan, China.
Distichophytum is a genus of extinct vascular plants of the Late Silurian (Ludfordian) to Early Devonian (Emsian), around 426 to 393 million years ago. The genus has a tangled taxonomic history, also being known as Bucheria and Rebuchia.
Thrinkophyton was a genus of Early Devonian land plant with branching axes. Known fossils are of Lochkovian to Pragian age.
Gosslingia was a genus of Early Devonian land plant with branching axes. Fossils have been from the Lochkovian to the Pragian, 419 to 408 million years ago.
Tarella was a genus of Early Devonian land plant with branching axes. Fossils came from Pragian age rocks.
Oricilla was a genus of Early Devonian land plant with branching axes. Fossils have been found from the Pragian to the Emsian.
Nothia was a genus of Early Devonian vascular plants whose fossils were found in the Rhynie chert in Scotland. It had branching horizontal underground stems (rhizomes) and leafless aerial stems (axes) bearing lateral and terminal spore-forming organs (sporangia). Its aerial stems were covered with small 'bumps' (emergences), each bearing a stoma. It is one of the best described early land plants. Its classification remains uncertain, although it has been treated as a zosterophyll. There is one species, Nothia aphylla.
Konioria was a genus of early land plant with branching axes. Known fossils are of Early Devonian age.
Deheubarthia was a genus of Early Devonian land plant with branching axes.
Danziella is a genus of extinct vascular plants of the Early Devonian. Fossils found in the Artois region of northern France were first described as Zosterophyllum artesianum, but a later review by Edwards showed that they did not fit the circumscription of that genus.
Wenshania is a genus of extinct vascular plants found in the Posongchong Formation, Yunnan, China, which is of Early Devonian age. Plants consisted of leafless stems with simple dichotomous branching, and bore spore-forming organs or sporangia all around the sides of stems. Wenshania is part of the broadly defined group of zosterophylls.
Ramoferis is a genus of extinct vascular plants of the Pragian stage of the Early Devonian, around 411 to 408 million years ago. It is considered to be a zosterophyll, one of a group of plants that were related to the ancestors of the modern lycopsids. Fossils were found in the Posongchong Formation in Guangnan County, Yunnan, in southwestern China, where they occur as compressions.
