A faint glimpse of another Rhynie
chert plant ?
Up to now, 7 species of "higher plants" have been discovered
in the
Lower Devonian Rhynie chert, every one with its own distinctive
features. None of them
has been found elsewhere. The latest ones, members of the larger
zosterophyll family thought to be related to the ancestors of the
clubmosses, were published in 1991 [1] and 2000 [2]. So it is worth
while looking for more.
Photograph and drawing:
Sporangium attached to a poorly preserved shoot
with tiny thorns
(above left), apparently not fitting
to any known species in the Rhynie chert.
Another zosterophyll ? Width of the picture 2.4mm.
A chert sample found in 2006 shows a faint structure which does not
seem to fit to any of the known species. A small bud-like
sporangium is seen attached sideways above a
slight kink of the shoot (below right). Unfortunately,
the preservation is poor, and the shoot seems to
be partially damaged or sqeezed. Also it is difficult to distinguish
between the plant remains and microbial coatings on them. What seems to
be a sturdy bristle might serve as an argument for an
affinity to the zosterophylls. There are smaller bristles on the
shoot (not seen here) but no needle-shaped ones, which seems
to preclude an
interpretation as Trichopherophyton,
the only plant in the chert known
to bear bristles. The shoot with sideways
attached sporangium resembles fragments
of
Salopella
[3].
The apparent scarcity of fossil remains of this plant could be due to
fast decay, similar as with Trichopherophyton,
which likewise had been
overlooked for a long time. Careful inspection of chert samples with
poorly preserved plant parts could possibly confirm the status of this
elusive plant as a new species in the Rhynie chert, of which it is not
known whether it represents an ecological niche with endemic species or
a more extended Lower Devonian habitat.
H.-J.
Weiss 2008
[1] A.G.Lyon,
D. Edwards: The first zosterophyll
from the Lower Devonian Rhynie Chert.
Trans. Roy. Soc. Edinburgh: Earth Sci.
82(1991), 323-332.
[2] C.L.
Powell, D. Edwards, N.H. Trewin: A
new
vascular plant from the Lower Devonian Windyfield chert,
Rhynie, NE
Scotland.
Trans. Roy. Soc. Edinburgh,
Earth Sci. 90(2000 for 1999), 331-349.
[3] D.
Edwards, U. Fanning: Evolution and
environment in the late
Silurian – early Devonian: the rise of the pteridophytes.
Phil. Trans. Roy. Soc. London
B 309(1985), 147-165.
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