Aglaophyton upward bend and cross-sections
What is new about the Rhynie chert
deutsche Version
Research activities concerning the chert are continuing lately, with results being published in scientific journals and via Internet [1,2]. A special issue of the Proceedings of the Royal Society Edinburgh [3] is the largest compilation of recent work on Rhynie chert in one volume, with ample lists of references to earlier work. Research was taken up recently at the Museum of Natural History, London, based on large amounts of chert from early excavations stored there.
Possibly the most beautiful and informative publication on the subject,
with 72 colour pictures, is available in Dutch [4].

Photograph: Upward bend of Aglaophyton. The orientation is indicated by "level bands" in former cavities of gas bubbles (big one below right) later filled with water. The slightly differing tilt indicates motion during silicification. (Sample: Rh12/91.1, found in 2006.)

Nowadays, progress in palaeobotany is sometimes hindered by the cumbersome procedure of publication: Usually a submitted paper has to be quite substantial and professional to get a chance of being accepted for publication. This precludes a quick exchange of information and ideas. The procedure of reviewing by experts does not always preclude erroneous publications. Quite a number of disturbing examples are presented under the heading Misconceptions, and there will be more of them, judging from experience.

Luckily, the Internet provides the means to overcome such obstacles. R. Kretzschmar, a lay fossil collector later employed at Naturkunde-Museum Chemnitz, Germany, had established his "kieseltorf" website [5], which verbally means "silicified peat". This had been a welcome opportunity to offer news based on own finds of Rhynie chert on that website since 2003. Also it had provided the encouragement to launch this "chertnews" website, with Rhynie chert as a main subject, in 2010. Deplorably, R. Kretzschmar had quit his job at the museum and deleted his successful "kieseltorf" website in 2017. One example of his activity is described in Fossil Wood News 15.

Every one of the numbered issues of Rhynie Chert News is based on own samples (with few exceptions) and is meant to offer something more or less new. Most of the observations are only small pieces in the big puzzle of palaeontology but some are of greater relevance. In the following, the new finds and insights derived from them are sorted into subjects.

The peculiar little sphere Pachytheca, once thought to be an alga but now listed together with the nematophytes among the "Enigmatic Organisms" [6], had never before been described as a fossil well preserved in chert. Hence, the sample from Rhynie is useful for comparison with the coalified samples abundantly found elsewhere. The discovery of a few more "Enigmatic Organisms" provides answers to long-standing questions but also raise new ones, or help to refute erroneous views.
It has been found out that the nematophyte Nematoplexus unexpectedly has much more to offer than its regular screw-like tubes. Apparently the often repeated assumption that the tubes grow and branch inside the obscure "branch-knots" and come out cannot be upheld. The tubes seem to emerge from the surface of the "knots" which should better be called clots
Some (or most ?) of the nematophytes consist of a lump of gel enclosing the tubes and protecting them against exsiccation in dry surroundings. The tubes of some nematophytes are surprisingly wide, 50-60-(70)Ám, with blank "glades" among the tubes.
Surprisingly, a small flat nematophyte with surface layer suggests a possible affiliation with fungi [10].
A tangle of tubes with patterned wall, similar or equal to the nematophyte Nematothallus pseudo-vasculosa, hitherto known as compression fossils only, has been found in chert, too.

Land plants
The curled-up tip of the rarest "Higher Plant" in the chert, Ventarura, is the only one found hitherto, and its existence will have to be taken into account in any reconstruction of the plant. A conspicuous coaxial tube inside the upper parts of Ventarura, thought to consist of sclerenchyma and to serve as a stiffening component, is shown to be no such.
The alleged "giant cells" in the epidermis of the sporangia and upper parts of Nothia are rather tube-like cavities brought about by controlled removal of numerous cell walls in the epidermis and below. They probably serve as vessels for a liquid deterrent protecting the plant against herbivores.
A recently widespread means of deterrence, bristles and spikes, had been invented by the "hair bearing plant"
Trichopherophyton . This is all the more remarkable since the defensive outgrowths are of different kinds: stiff short bristles (many) and flexible long hairs (few), apparently to keep off different herbivore species.   
Even the most abundant plant in the chert, former Rhynia major re-named Aglaophyton major, has provided new facts: The undulating growth does not result, as previously assumed, from a succession of upward growth and falling over but from the ability of the upright shoot to actively turn downward, then upward again as in the above picture. (The justification for the questionable change of name has been strongly doubted [7].)

Green Algae
The charophyte clade, already well established in the Devonian, has provided a surprise in 2015, based on a sample found in 2013: It may well be an archetype dating back to times when the charophytes had not yet developed the well-known gyrogonites. In addition to the sample mentioned here, several more samples with the unknown charophyte lacking gyrogonites have been found since. Specialists on charophytes wondering about the apparent absence of gyrogonites in the Rhynie chert are reluctant to accept the explanation based on plain evidence offered here [9].
Another unknown charophyte, found in only one sample, is distinguished by spherical (?) enclosures apparently formed by surrounding tube-like cells, similar as with Coleochaete, a possible ancestor of land plants.
Mentioned here for completeness but probably of minor importance is the discovery of another filamentous alga.

Yellow-Green Alga (Xanthophyte)
One of the latest discoveries (2014) concerns mm-size vesicles, apparently either filled with large numbers of nuclei or empty, thus strikingly resembling the extant xanthophyte Botrydium.

Brown Alga ?
Recently a cm-size bag-like plant has been discovered which does not seem to fit into the Rhynie chert plants but reminds one of Laminaria .

The filamentous cyanobacterium Croftalania has proved surprisingly versatile as it offers shapes of a complexity never expected from the lowly microbes. The big showy formatios were first described in 2007 [11] but certainly had been known before.   

Recent finds of the well-known spider-like trigonotarbids have also provided new insights. An uncommonly large trigonotarbid has been cut incidentally nearly parallel to but slightly off its midplane so that the two book lungs on its right half are seen, which is a very rare sight. More often than expected, two trigonotarbids (or their moults) have been found near each other, which requires an explanation.
Arrangements of hairs on trigonotarbid mouth parts are possibly meant for safe handling of nutrient-rich liquid from partially liquefied prey, avoiding immediate contact.
The tube inside the crustacean Ebullitiocaris is apparently not the gut but the rudimentary rear part of the body.  

The unquestioned highlight among the own discoveries described in Rhynie Chert News is a quite unexpected dramatic scene, a snapshot of aquatic life in the shallow pools fed by hot springs at Rhynie 400 million years ago, featuring the most ancient rotifer ever seen, at the instant of being trapped by quick silica gel formation while attacking an unknown spherical cyanobacteria (?) colony.  

The Rhynie chert is also known for its various fungi [8], most often seen as hyphae. Some of them have not yet been described. Worth mentioning are an uncommon chytrid resembling Trewinomyces and conspicuously wavy hyphae, the apparently first fossil evidence of a particular type of mycoparasitism easily recognized by irregularly undulating hyphae as known from extant Trichoderma. (The latter has been thoroughly investigated and is even applied as a fungicide of commercial relevance.) 

The series of Rhynie Chert News will be successively extended.

H.-J. Weiss      2005,   updated in 2010, 2011, 2014, 2016, 2017, 2019, 2020,  re-arranged in 2020,
updated in 2021

[1]  (up to 2004)
Google: Rhynie research index Muenster  (up to 2000)
[3]  N.H. Trewin, C.M. Rice (eds.): The Rhynie Hot Spring System,  
       Trans. Roy. Soc. Edinburgh, Earth Sci. 94(2004 for 2003), Part 4.
[4]  H. Kerp, H. Hass: De Onder-Devonische Rhynie Chert,
       Grondboor & Hamer 58(2004), 33-51.
[5] , English version. (deleted in 2017)
 T.N. Taylor, E.L.Taylor, M. Krings: Paleobotany, Elsevier 2009.
[7]  Dianne Edwards : A review of the sporophytes of embryophytes in the cherts at Rhynie,
      Trans. Roy. Soc. Edinburgh, Earth Sciences 94(2004 for 2003), 397-410.
[8] T.N.Taylor, M. Krings, E.L. Taylor: Fossil Fungi, Elsevier 2015.
[9]  M.
Feist: Comment on manuskript (2019)
[10]  R. Honegger, D. Edwards, L. Axe, Ch. Strullu-Derrien: Fertile Prototaxites taiti: a basal ascomycete with inoperculate, polysporous asci lacking croziers.
      Phil.Trans. Roy. Soc. B 373 (2017): 20170146.
[11] M. Krings, H. Kerp, H. Hass, T.N. Taylor, N. Dotzler: A filamentous cyanobacterium showing structured colonial growth from the Early Devonian Rhynie chert.
      Rev. Palaeobot. Palyn. 146(2007), 265-276.

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