in one chert sample
This fossil resembles the nematophyte Nematothallus, which had been found as compresssions only but never
in chert. The similarity has
been pointed out by P.K. Strother
[1,2], hence it is called Nematothallus
It is also shown in Rhynie
Chert News 107
Formerly separate fragment of gel with Nematothallus,
in bluish chalcedony from silicified water of the swamp containing Nematoplexus
Image width 1.38mm.
discovery of Nematothallus in
chert sample incidentally containing the rare fossil
seemed to support the
assumption that Nematoplexus
"may represent the permineralized equivalent of Nematothallus" .
one of the reasons why the disputed nematophytes
are considered here once more.
The statement in  that "Nematophytes
appear to generally comprise networks of intertwined spirally coiled
tubular cells" is not true.
Fig.2 (left): Nematothallus, detail
from Fig.1: tube wall patterns consisting of rings and spiral
fragments of 19-23Ám diameter. Image
Photograph by G. Schmahl.
The lump in Fig.1
seems to have separated from a bigger lump or layer of Nematothallus
in gel and got near Nematoplexus also grown in that habitat. All together silicified
such that the two nematophytes are found now within a mutual distance
of mere 3cm.
Part of the left end of the Nematothallus lump
is seen magnified in Fig.3.
Fig.3: Nematothallus parts of various aspect, enlarged part of Fig.2 above left.
Image width 0.3mm. Photograph by G. Schmahl.
A few details are worth mentioning: Not
the tube walls but the reinforcing patterns have been preserved. The
diameter of the tubes had probably been about the same size. Conspicuous is the variable diameter of one of the tubes.
As seen above right, the tube wall pattern is not always ring-like or
spiral-like but can be rather rugged. The nature of the bubble
on the left is not known.
A narrow tube, diameter
about 4Ám, indicates that there may be more hidden structure. Tubes of 1.5-3Ám among
the big ones have been reported from Nematothallus
compressions [1,2], and possibly the thin line fragments in Figs.1,2 are
the remains thereof. Small tubes with sizes of 3Ám and below, in addition to the larger ones, are also found close to Nematoplexus "branch knots", as seen in Rhynie
Chert News 133 .
Despite of these similarities it is not justified to regard Nematoplexus
as a form of Nematothallus.
Fig.4 (right): Nematoplexus
"branch knot" with two types of spiralling tubes emerging, diameters
10Ám and 16Ám, also one patterned tube of dubious affiliation, 24Ám.
Image width 0.6mm, same scale as Fig.2.
The conventional term "branch knot" in the
literature on Nematoplexus
origin of the tubes by branching. The
Chert News 134
(there Fig.2) favours a different view: There, two
10Ám-tubes, each one with a slightly broadened "foot", seem to
stick to the poorly defined surface of a central clot with about 75Ám
diameter. There is no indication that the tubes had been produced by
branching inside the clot. In this Fig.4, the central clot of the "knot" is
of about the same size. Although its surface is less well defined, it
can be assumed that here, too, the tubes emerge from the surface. Also
there would hardly be enough room for many branching tubes inside.
Near the knot in Fig.4,
the tubes have not yet formed their ideal
bigger tube in Fig.4 emerges from the depth below the
knot in a half circle towards the
cut plane where it is cut off and hence no more seen, then dives down
below the cut plane above left and thus is in the picture again. Nearby
a big tube with patterned wall,
looks surprisingly similar to the Nematothallus tubes
in the above pictures.
(For easy comparison,
Figs.2 and 4 have got the same scale.) It
be a stray relic from decayed Nematothallus,
or else it could be one of the less abundant patterned tubes seen
emerging from "branch
knots" of Nematoplexus
a peculiar fact, the patterned tubes in these pictures are transparent,
without a visible wall, but the
spiralling tubes from
same sample (Fig.4)
appear dark, with more or less translucent
Even though the
suggestion in  that Nematoplexus
"may represent the permineralized equivalent of Nematothallus"
is not at all substantiated, intriguing questions remain:
Is there a reason why it is not unlikely that the two rare nematophytes are together in one piece of chert ?
Why are the worm-like tubes with patterned wall occasionally emerging from Nematoplexus "branch
knots" surprisingly similar to those of Nematothallus ?
Sample: Rh9/86, 0.28kg, 2003.
P.K. Strother: Clarification of the genus Nematothallus Lang: J.
Paleont. 67(1993), 1090-1094.
 W.H. Lang: On the
plant-remains from the Downtonian ... . Phil. Trans. Roy. Soc. London B
E.L.Taylor, M. Krings: Paleobotany, Elsevier
error on Fig.6.9: scale bar not 100Ám, rather 20Ám ?)
Chert News 137