Enigmatic knots of an enigmatic organism

knotsThe discovery of an unexpected big detail somehow related to the twice enigmatic Nematoplexus [1] known for its unique spirals dates back to only about 3 years ago (Rhynie Chert News 71). The spiralling tubes of this rare fossil, described in [2] under the heading Enigmatic Organisms, are supposed to be produced inside "branching knots" although tube branching has never been seen there.
Most often, knots are found in areas with scattered spirals (Figs.1,2). Less often, solitary knots of various aspect are found in areas where regular spirals are absent (Figs.3-9) but usually not far away in the chert sample.
The solitary knots add to the mystery surrounding Nematoplexus. Attached to these knots are tubes differing in shape and size from the "normal" spirals with their remarkably constant curvature and twist, for reasons unknown. The much bigger tubes and related knots seen in the three images below right are quite surprising for their features:
 - tube diameters >20Ám, 30Ám at the base,
 - tubes nearly straight or slightly curved,
 - found only in samples with the usual Nematoplexus spirals.

Fig.1: Nematoplexus spirals and parts thereof seen in pale bluish chalcedony; big dark "branching knot", small one near the middle of the image. Note that there is a spiral with three turns above the knot on the left and another one right of the middle, with one tangent of the spiral incidentally being perpendicular to the picture plane so that the spiral looks like an inclined "3". Width of the picture 1.73mm.


Figs.2-9: "Branching knots" of various aspect, with or without spiralling tubes nearby. Same scale as Fig.1, width of the pictures 1.38mm.

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With the circular cross-sections of the cut-off big tubes in the last image clearly seen, the question suggests itself what the onsets of the tubes inside the knot do look like.
Are they all interconnected or do they grow from separate points ? Apparently there is no answer to simple questions of this kind at present.
Individual non-spiralling tubes, often slightly bigger than those of the nearby spirals
, are seen as stubs in Figs.1,2. These irregular tubes may show annular or spiral wall patterns. Perhaps the non-spiralling tubes in the images on the left belong to this type.
Dozens of tubes with patterned wall have been found loosely arranged in a translucent cluster
resembling Nematothallus (see Rhynie Chert News 107), only millimeters away from the typical Nematoplexus spirals but in no way connected to the latter.
As another extension of the Nematoplexus enigma, the regularly wound spirals, too, are occasionally seen with distinctly differing sizes, even at the very same spot of the sample (
Rhynie Chert News 106, there Fig.2). Also it appears that tubes with diameters smaller than those of the regular spirals can be weakly curved or nearly straight, like the one seen crossing the last image here. Furthermore, very thin slightly curved tubes (4Ám ?) apparently come out of the big black knot.
One may wonder how the various details thought to be parts of Nematoplexus can possibly be mutually compatible so that they can be regarded as aspects of one species. Otherwise they might represent different species grown very near to each other in places attracting nematophytes. One might even suspect that different nematophytes could have more or less united to form a kind of symbiosis.
In view of the variety of structural features associated with Nematoplexus, it can be expected that this nematophyte will yield more surprises with more finds turning up in Rhynie chert samples stored in collections.
Samples from own collection:
Rh6/102 (0.03kg) found by S. Weiss in 2003: Figs.1,5,7;
Rh9/86 (0.28kg) own find in 2003,
Part 2: Figs.2,4,6,8 (left column of images);
Rh15/79 (0.27kg) obtained from
Barron in 2014, Part 1: Fig.9, Part 2: Fig.3. 

H.-J. Weiss       2016

[1]  A.G. Lyon: On the fragmentary remains of an organism referable to the nematophytales, from the Rhynie chert, Nematoplexus rhyniensis.
      Trans. Roy. Soc. Edinburgh 65(1961-62), 79-87, 2 plates.        (Scale error on Plate I Fig.1: not x19 but x1.5)
[2]  T.N. Taylor, E.L.Taylor, M. Krings: Paleobotany, Elsevier 2009.
126

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