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.
Nematophytes
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)µm, 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 Nematothalluspseudo-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 xanthophyteBotrydium.
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 .
Cyanobacteria
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.
Creatures
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.
Fungi
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]
www.abdn.ac.uk/rhynie
(up to 2004)
[2] 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] www.kieseltorf.de
, English version.
(deleted in 2017)
[6]
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.
