A new find of the enigmatic plant Nematoplexus
|Nematoplexus rhyniensis can immediately be recognized by
its peculiar anatomy. It is mainly made up of a tangle of wound tubes which
looks chaotic at first sight but surprisingly reveals more than one sign
of orderliness (Fig.1): The tubes are wound into a rather regular thread
which is always right-handed. The diameter of the thread lies between the
bounds of 0.08 and 0.12 millimeters, and the pitch of the thread seems to
equal its diameter.
There are a few more plants consisting of a felt of tubes, but none of them has got its tubes wound into a thread. They are called nematophytes, which means filamentous plants. They clearly differ from the various extant types of filamentous algae. What they may have in common is some kind of gel binding the tubes into a larger entity and keeping out floating debris and aquatic creatures.
Nematoplexus rhyniensis was described by A.G. Lyon on the basis of only one chert sample of a rare variety without the usually abundant remains of terrestrial plants. The sample presented here is of the same type, and it is distinguished by the presence of the aquatic crustacean Castracollis, which has been repeatedly found recently in samples of the common chert type with flooded terrestrial plants.
The present specimen of Nematoplexus (Figs.2-4) has been discovered
by inspecting the smooth surface of a chert layer fragment of 0.28kg. The
typical coil fragments are seen scattered over a patch of about 5 mm across.
Judging from the much larger specimen in Fig. 1 from Lyon (1961-62), this
patch is not representative of the whole. So it does not show structures
other than the smooth coiled tubes, in a more or less broken state.
With the presently sparse fossil evidence of Nematoplexus, which is apparently restricted to the type specimen and the sample described here, it seems not justified to regard the bigger variety as a new species. This may be reconsidered as soon as more finds revealing other details become available.
H.-J. WEISS 2009