Another tangle of tubes in chert

The nematophytes, from palaeobotany monographs also known as Enigmatic Organisms, are not often seen in the Rhynie chert. Judging from the few samples hitherto found, they come in tangles of tubes which can be more or less aligned, or even strictly aligned as with Pachytheca. There are several species, among them apparently unnamed ones. Some of them seem to consist of smooth-walled tubes only, as those presented in
 Rhynie Chert News 13, 30, 40, 46, 92, 98, 99Others consist of a combination of tubes with smooth walls and others with spirals or annular rings on the walls [1].
Fig.1: Nematophyte tube fragment, 26Ám, spacing mostly 5-6Ám. Width of the image 0.8mm.

The logic behind the different types of tubes and their possible mutual relation remain obscure. They are thought to somehow originate within "branch knots" of Nematoplexus [1] but the present sample does not provide evidence for this although a few branch knots surrounded by smooth-walled screw-like tubes are seen only 3cm away. The tubes with patterned walls are found as scattered fragments only, similar as in Fig.1, with one quite unexpected exception seen in Fig.2, where the large tubes seem to be embedded in a separate lump of gel with a tangle of poorly visible tiny filaments.
As noticed by P. Strother [2], the fossil in Fig.2 strongly resembles Nematothallus pseudo-vasculosa known from compressions [3]. The size data are roughly compatible, including the dimly seen tiny filaments in Fig.2 which seem to correspond with "tubes between 1.5 and 3Ám in diameter" seen on the lectotype of that organism [3,4].
Similar as with the tube fragments scattered sparsely throughout the chert, the tubes in the gel lump do not show branching nor other remarkable features, perhaps except for one peculiarity poorly seen above left: A big tube suddenly reduces its diameter to less than half.
What looks like a series of orderly turns of a screw, as in Fig.1 below right, is often interrupted by disorder due to merging or branching turns, as repeatedly seen in Fig.2.

tube patch
Uncommon assemblage of nematophyte tubes as a separate patch, probably of gel , with various diameters centered around an average of 20Ám, and a wide variety of spacings between turns.
        Width of the image 1.9mm, same scale as above.

Drawing conclusions from only one sample may not be justified here but formulating questions may be appropriate. The tubes with patterned walls in this sample are not seen near branch-knots of Nematoplexus. Hence similar tubes seen elsewhere attached to branch-knots pose the question what makes them do so. Even in cases where there is no connection the question remains why patterned tubes are found near smooth-walled screws of Nematoplexus, and particularly, why this veritable 3D-version of Nematothallus pseudo-vasculosa, too, seems to prefer a place where Nematoplexus is near.   

Finally it may be mentioned that this sample of mere 0.28kg found in 2003 has offered several remarkable items: Nematoplexus with tubes larger and smaller than hitherto known (2009), Castracollis eye (? 2015) and unidentified moults, an unknown archetypal charophyte (2016), and possibly the first 3D-version of Nematothallus pseudo-vasculosa, (2017).   

H.-J. Weiss    2017

[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]  P.K. Strother: private communication (2017).
[3]  P.K. Strother: Clarification of the genus Nematothallus Lang: J. Paleont. 67(1993), 1090-1094.
[4]  W.H. Lang: On the plant-remains from the Downtonian ... . Phil. Trans. Roy. Soc. London B 227(1937), 245-291.

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