Nematophytes vs. liverworts
which literally means "filamentous plants" (Fig.1), are
still so poorly understood that lately they have been tentatively
listed under the heading "Enigmatic Organisms" . This poses a
challenge to look for explanations .
Fig.1: Nematophyte in Rhynie chert with nearly parallel tubes in
cross-section and two dark clots supposedly consisting of a tangle of
much smaller tubes; undescribed species. Width of the picture 1.26mm.
2016: Closer inspection has shown that the big clots seen here do not
consist of a tangle of tubes and thus differ from the "branch
knots" known from other nematophytes. See Rhynie
Chert News 92, This does not affect the below conclusions.)
Recently it was tried, with much effort, to gather evidence for the
idea that some or most nematophytes are ancient liverworts . This
idea is based on two guesses:
- The tubes constituting the nematophyte are
rhizoids of some liverwort.
- The cuticles with cellular patterns known as
together with coalified tangles
of filaments or tubes, belong to ancient
The idea of a liverwort connection has quickly spread among the
scientific community and more or less been accepted without checking,
judging from quotations like this: "One interesting hypothesis suggests
that several of the enigmatic Cambrian to Devonian fossils
traditionally included in the nematophytes may represent remains of
ancient liverworts ... ." Apparently this hypothesis has never been
seriously doubted, except for the present contribution based on a very
few nematophyte specimens recently found
in the Rhynie chert .
The dark clots among the mass of tubes in Fig.1, which are a typical
feature of some nematophytes, preclude an interpretation of the tubes
as rhizoids. (The clots apparently consist of a close tangle of much
smaller tubes whose cross-sections are seen as tiny bright dots. The
existence of the clots is one of the enigmas connected with the
Fig.2: Same sample as Fig.1, with a cellular pattern interpreted here
as boundaries between gel coats around the tubes.
See also Rhynie
Chert News 30
The problem of how the nematophytes could possibly produce a cuticle
with cellular aspect can be separated into two parts: How the pattern
is brought about, and how the cuticle is made.
Fig.2 suggests an
explanation for the origin of the pattern: Every one of the tubes
surrounds itself with a coat of gel. The gel coats taken together make
a continuous mass of gel, with the boundaries between them still there
and, under favourable conditions, seen as a cellular pattern.
It remains to be explained how the pattern can be imprinted onto a
cuticle. This is attempted with the drawing in Fig.3. Here it is
assumed that the boundaries between the gel coats seen on a cut and
polished chert face in Fig.2 make a network of grooves on the surface
of the lump of gel, possibly deepened by drying.
Fig.3: Schematic drawing illustrating the possible formation of a
cuticle with cellular pattern (Nematothallus
aspect) on the gel surface
of a nematophyte. (The shape of the tube ends is not known.)
The tubes may produce a cuticle precursor substance and release it into
the gel where it moves by diffusion towards the surface where it
accumulates, spreads, fills the grooves, and polymerizes into a
protective cuticle with Nematothallus
aspect, which is decay-resistant
as known from the cuticles of land plants.
This is the proposed solution of the long-standing Nematothallus
problem, without invoking the idea of a liverwort connection. It is
essentially based on the presence of gel as a constituent of
nematophytes which reveals itself in the Rhynie chert but not with the
compressed specimens found elsewhere.
solution is proposed for the Cosmochlaina
forming from liverwort rolls as imagined by
et al. (2010) .
The vanishing evidence for the liverwort interpretation of nematophytes
affects the latest fancy hypothesis declaring the enigmatic huge
trunks to be rolled-up and subsequently silicified liverwort mats as
illustrated in Fig.4 .
The unique preservation of nematophytes in the Rhynie chert,
non-compressed and suggesting the presence of gel between the
filaments, allows the following conclusions to be drawn :
- The idea of nematophytes being related to
liverworts, brought up in 2004 and widely spread since, is
- The latest elaboration of the liverwort idea in
2010, which is the introduction of liverwort rolls as another
might be remembered for its inventiveness but should
better be forgotten.
Taylor, E.L. Taylor, M. Krings:
Weiss : "Enigmatic Organisms" – Insights derived
Palaeobotany - Palynology Conference 2010, Budapest.
Graham, L.W. Wilcox, M.E. Cook, P.G.Gensel :
Resistant tissues of
modern marchantoid liverworts resemble enigmatic Early Paleozoic
Proc. Nat. Acad.
Sci., USA, 101(2004), 11025-29.
Strother : Clarification of the genus
J. Paleont. 67 (1993), 1090-94.
Steur, W. v.d.Brugghen : Nematothallus – een
uit het Siluur en het
Vroeg-Devoon. Grondboor & Hamer (1998) Nr.2, 28-35.
Weiss : Nematothallus:
How the filaments produced a cellular cuticle. (Oral presentation)
Palaeobotany - Palynology Conference 2010, Budapest.
Graham, M.E. Cook, D.R. Hanson, K.B. Pigg, J.M. Graham:
Structural, physiological, and stable
carbon isotope evidence that
enigmatic Paleozoic fossil Prototaxites
formed from rolled liverwort
Am. J. Bot. 97(2010), 268-275.
Acknowledgement: Thanks are due to Christopher Taylor ,
for drawing attention to the above painting and related discussions by
means of his blog, which instigated the presentation .