Rinistachya

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Rinistachya
Rinistachya hilleri.jpg
Specimen showing the whorl with preserved leaves
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Division: Polypodiophyta
Class: Polypodiopsida
Subclass: Equisetidae
Order: Sphenophyllales
Genus: Rinistachya
Prestianni & Gess, 2019
Species:
R. hilleri
Binomial name
Rinistachya hilleri
Prestianni & Gess, 2019

Rinistachya is a genus of Late Devonian sphenopsid, currently containing one species, Rinistachya hilleri. [1] It comprises the only sphenopsid as yet known from the Devonian of Gondwana, and is currently known from only a small number of specimens collected from the main fish layer/lens (MFL) black shale within the Witpoort Formation (Witteberg Formation, Cape Supergroup) at Waterloo Farm, Makhanda. [2] It is currently interpreted as a small-sized herbaceous plant. [1]    and 'exhibits a novel architecture' that includes apparently plesiomorphic characters, reminiscent of the organisation of the Iridopteridales (including the production of two types of laterals at one node, the location of fertile parts in loose whorls on lateral branches and an organisation of the fertile parts in which they branch several times before bearing distally elongate sporangia). [2] Other characters unambiguously nest Rinistachya within the Sphenopsida (including presence of planate and slightly webbed ultimate appendages and lateral strobili made of successive whorls of fertile leaves with fertile parts located at their axil). This provides strong support for a close relationship between Sphenopsida and Iridopteridales. [2] It is the only known high latitude sphenopsid known from the Devonian, the only other 3 genera, Eviostachya, Hamatophyton and Rotafolia being of palaeotropical provenance [2]

Contents

Description

The main stem is approximately 80 mm long and consists of a succession of nodes and internodes. From the examined material, the stem was characteristically slightly wider at the nodes and of the number of nodes observed, only one was well preserved. Internodes range from 0.9-1.2 mm in width with the longest being 40 mm. Fertile nodes are inserted in whorls of up to three axes at each node. These fertile nodes are between 0.4 to 0.5 mm in width. Each node has a whorl of leaves inserted together with a whorl of fertile parts. In well preserved parts of the specimens, fertile leaves are linear in shape and appear to be divided approximately two-thirds of their total length. Fertile leaves are weakly recurved on the inside of the leaves and are approximately 10 mm long. [2]

Etymology

The genus name is derived from an isiXhosa name for the Makhanda city (former Grahamstown) while stáchya is a plural form of the Greek word “stáchys” referring to spikes. The species epithet hilleri is in honour of Professor Norton Hiller in recognition of his role as the original supervisor of Dr Gess’ excavations at Waterloo Farm. [2]

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Waterloo Farm lagerstätte site in South Africa with a wide range of fossils from high-latitudinal Gondwana

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<i>Octochara</i>

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<i>Hungerfordia</i> (alga) Extinct genus of algae

Hungerfordia is a genus of presumed marine algae first described by Fry and Banks in 1955 in describing Hungerfordia dichotoma from Late Devonian strata. It has been interpreted as a probable brown (Phaeophyte) algae though the possibility that it represents a red (Rhodophyte) alga is not excluded - the taxonomic challenge being that modern red and brown algae are differentiated on the basis of colour and cellular structure which are not preserved in the fossil taxa. Douglas and Jell (1985) suggested that Buthotrephis trichotoma and B. divaricata should furthermore be transferred from Buthotrephis to Hungerfordia. A further species, Hungerfordia fionae from the Late Devonian of South Africa is known from the largest sample, analysis of which suggests that variations used to differentiate between H. dichotoma and H. trichotoma may represent growth variations accountable by a single taxon. Hungerfordia fionae fossils are as yet only recorded from the Waterloo Farm lagerstätte in Makhanda, Eastern Cape, South Africa and were first mentioned in the literature in 1991 as ‘terminally-lobed algae’ by Fiona Taylor. With further excavations, in subsequent years, hundreds of specimens of Hungerfordia have been collected, which are housed within the Devonian Ecosystems Laboratory, Albany Museum in Makhanda, Eastern Cape -. Hungerfordia fionae comprises dichotomous axes and is differentiated from other species by the presence of small bud-like appendages along the margins, which are preserved in a minority of specimens, and may more commonly have been shed in life or during transport. These have been compared to buds produced during the fertile phase of modern Rhodophyte algae. It is believed that H. fionae probably lived in the more marine dominated portion of the Waterloo Farm estuarine system and were drifted further into the estuarine lake system through tidal action. Here they were preserved in large numbers due to anoxic bottom water and still water conditions that allowed for unusual preservation of soft tissues. They are often preserved alongside charophyte algae, representative of fresh to brack conditions, demonstrating the dynamic salinity clines in the estuarine environment, as well as fragments of terrestrial plants and estuarine fauna.

Yeaia is an extinct genus of brown algae known from the Silurian and Devonian of southern hemisphere locations.

Leptophloeum is an extinct genus of vascular plants in the lycophyte clade. It is widely distributed being, known from the Laurasian and Gondwanan settings between the Devonian and Early Carboniferous periods.

Kowieria is an extinct genus of lycopsid from the Late Devonian from Waterloo Farm, containing the single species Kowieria alveoformis. As of 2021 it is being characterised as incertae sedis. It was first described in 2017 from a black shale layer interbedded with quartzite strata of the Famennian aged Witpoort Formation.

References

  1. 1 2 TAYLOR, T (2009), "Introduction to Paleobotany, How Fossil Plants are Formed", Biology and Evolution of Fossil Plants, Elsevier, pp. 1–42, doi:10.1016/b978-0-12-373972-8.00001-2, ISBN   978-0-12-373972-8 , retrieved 2021-06-21
  2. 1 2 3 4 5 6 Prestianni, Cyrille; Gess, Robert W. (2018-11-28). "Rinistachya hilleri gen. et sp. nov. (Sphenophyllales), from the upper Devonian of South Africa". Organisms Diversity & Evolution. 19 (1): 1–11. doi:10.1007/s13127-018-0385-3. ISSN   1439-6092. S2CID   53811583.