- more details, more questions (2)
first described in 1961 , appears to become
ever more enigmatic as new details are discovered in the few fossil
samples available now. (For an
introduction see Part 1.)
there is one detail which is seen more clearly here: While the
screw-like tubes usually "form a loose plexus and frequently appear to
lie in lax interwoven coils" , thus making a confusing aspect, this
sample offers the rare opportunity to see two of them separately.
Incidentally, 5 turns of the screw are seen in either case: from
outside in Fig.1 but from within in Fig.2 where one half of the thread
has been cut off so that the ends of every half turn of the tube point
out of the picture towards the observer.
The coherent tubes seen
with several turns allow to confirm the characteristic rule stated
earlier: thread diameter roughly equal to the pitch of the thread. (See
Chert News 29.)
Figs.1,2 (right): Screw-like Nematoplexus
tubes, larger than those in : tube diameter about 13Ám,
diameter 130Ám. Width of
the images 1mm, same scale as in Part 1.
Fig.3 (left), detail of Fig.2, turned: Smallest spiralling tube, thread diameter 30Ám, tube about 4Ám.
Image width 0.2mm, photograph by G. Schmahl.
addition to the big surprises, the big slightly curved tubes shown in
Part 1 and to be discussed here once more, there have been big
surprises small in size. One of them is the tiny screw-like tube in
Fig.3, the only one of its kind, slightly disarranged here. There
indication in which way it might be related to the "normal" screws. Its
thread is even narrower than the tube with spiral and annular wall
pattern in Fig.6. Hence, one must take care not to confuse the tiny
screw-like tubes with the spiral wall patterns of similar size.
non-typical structure is the one seen in Fig.4. It looks like a piece
of wire repeatedly bent into a tangle and placed immediately below the
cut face. Some part has been cut off above left so that there seem to
be two ends. Such kind of tangle has neither been seen with Nematoplexus
nor with any other nematophyte. It differs distinctly from the "branch
knots" since apparently no purpose can be assigned to them while the
branch knots can bring forth more than a dozen tubes extending
into any direction from the enigmatic interior
of the knots. (See
Fig.4 (left): Nematoplexus tube,
10Ám, bent into a tangle shaped as a coarse-meshed cage without visible
connection to other tubes. Width of the
8 big slightly curved Nematoplexus
tubes with smooth wall, 25Ám, all of them apparently coming from a
big branch knot broken off here, and vanishing from sight in the depth,
2 thin tubes, 5Ám (?), on the left, one of them screw-like, thread
diameter 90Ám, another one slightly
Width of the image 1mm, same scale as Figs.1,2.
These pictures vizualise part of the problems encountered when trying
to make sense of Nematoplexus.
The screw-like tubes in Figs.1,2 are similar to but bigger than those
in . The structure in Fig.3 does not fit anywhere. In
Fig.5, the big slightly
tubes with smooth wall, seen as a bunch with apparently common origin
in a branch knot above the picture plane, had not been seen in the type
specimen . One would be tempted to assign them to another species if
there were not the fact that they are always found near or between the
screw-like tubes. Since there are 8 of them diving into the half space
behind the picture plane, one can assume that about the same number,
not seen here, had come towards the observer before a crack in the
chert layer had removed the big branch knot and exposed the tubes seen
here on the raw surface of the sample.
Fig.6 (left): Big tube with wall
thickenings, short fragment, 33Ám wide,
matter is complicated by the fact that there are miniature screw-like
and very thin slightly curved tubes as seen in Figs.3,5.
conspicuous complication, as already mentioned in , comes from the
tubes of various sizes with helical or annular wall thickenings
(Fig.6). They do not form screws, are most often seen
loose fragments but are also seen attached to the smaller kind of
branch knots. Apparently they are not related to the big branch knots
where the big smooth-walled tubes come from (Fig.5).
All presently availabe pieces of information about Nematoplexus
taken together do not make a consistent view. As long as it is not
known in which
way the tubes of various type, shape, and size are mutually related,
and possibly other nematophytes have to be aptly called "enigmatic
All pictures in Parts 1 and 2 have been taken from one
chert sample of 0.27kg, Rh15/79, obtained from Barron in
Addition 2018: Fig.3 has been added and the figures have been re-numerated.
On the fragmentary remains of an organism referable to the
from the Rhynie chert, Nematoplexus
Trans. Roy. Soc. Edinburgh
65(1961-62), 79-87, 2
error on Plate I Fig.1: not x19 but x1.5)