Nematoplexus - Where the spirals come from
deutsche Version

Nematoplexus wound tubesThe enigmatic "branch-knots", scattered among the spiralling tubes of the enigmatic organism Nematoplexus seldom found in the famous Rhynie chert [1], have been thought to be places where the tubes branch profusely although a spiralling tube has never been seen branching.

Fig.1: Spiralling tubes of Nematoplexus and related "knots".
        Image width 1.3mm.

As seen in Fig.1 (reproduced from Rhynie Chert News 71 ), the tangle of randomly distributed tubes with dark "knots" in between is confusing, all the more so since straight or weakly curved tubes may also be present: Rhynie Chert News 51, 71 .
Higher magnification and other illumination have revealed that the knot on the right seems to consist of two neighbouring ones. A small protruding part of the big black knot in the depth of Fig.1 on the right is seen on the left of Fig.2. (Note that Fig.2 is turned to the left with respect to Fig.1.)
By lucky coincidence, a small separate knot, not noticed in Fig.1 but seen in the middle of Fig.2 now, is divided by a tilted crack plane reflecting the incident light so that half the knot, left of the divide, is illuminated from below while the other half, right of the divide, keeps in the shade. (The off-white angular mineral platelet can serve as a mark for comparison with Fig.1. The bright white spot below is an irrelevant light reflex from applied oil.) The colourful illumination is due to a thin deposit of iron oxide on the reflecting crack face. Nematoplexus "knot"

Fig.2: Small "knot" incidentally divided by a crack in the chert reflecting the incident light. Image width 0.3mm. Photograph by Gerd Schmahl.

Most interesting is the junction of an 11Ám-tube to what seems to be the indefinite surface of the knot: Contrary to the common belief due to the established term "branch-knot", the tube is not produced by branching. The same can be expected from the other tubes. One tube right of the divide, for example, is wider than normal where it emerges from the knot.
In addition to the tube diameters of 10-12.5Ám in Fig.2, there is only one clearly seen 4Ám-
tube and a straight one with 17Ám. (More non-spiralling tubes are present at other places in this sample.)
Finally it can be stated that the spiralling tubes
of Nematoplexus seem to emerge from the so-called branch-knots without any branching.
Sample: Rh15/79, Part 4, obtained from Barron in 2014.
Annotation 2020: For a discusion of the subject in a wider context see Rhynie Chert News 152.

H.-J. Weiss     2018  2020

[1]  A.G. Lyon: On the fragmentary remains of an organism referable to the nematophytales, Nematoplexus rhyniensis.
      Trans. Roy. Soc. Edinburgh 65(1961-62), 79-87, 2 plates.        (Scale error on Plate I Fig.1: not x19 but x1.8)
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