Another filamentous alga in the Rhynie chert
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alga filaments in Rhynie chertThe alga filaments described here have been seen on a cut face of only one chert sample on an area of about 1mm2, as essentially covered by Fig.1. They seem to be liable to fragmentation, possibly due to partial decay. Apparently the decay had affected the cells differentially: Most of them seem to are more or less shrunken but some seem to are not (Fig.2). Even one of the best-preserved cells (Fig.2) does not reveal what has happened to its content prior to and during silicification, and what to think of its fossil content.
Owing to their rare presence in the Rhynie chert, filamentous algae (other than charophytes or cyanobacteria) seem to have been investigated only once [1] and never since*.
The cell sizes of this alga differ significantly from those of either species described in [1]. Considering that the narrower cells in Fig.1 may have shrunken, the original width and length seem to be about 20Ám and up to 50Ám.
For comparison, the cells of
Mackiella rotundata [1] are much wider, 28-40Ám, and shorter, 23-41Ám. The cells of Rhynchertia punctata [1] are narrower, 8-16.5Ám, and shorter, 16-40Ám. Hence, this alga may be regarded as a not yet described species

Fig.1: Randomly arranged filamentous alga fragments in chert. Image width 1.3mm.

Fig.2 (below): Detail of Fig.1 (right of the middle), cells in various states of decay. Image width 0.2mm. Photograph : Gerd Schmahl, Dresden.
alga filament part

 Sample in the collection of Steffen Koehler, Meissen, collected decades ago by Brian Beveridge, Gloucester,
      on the now protected site formerly owned by A.G. Lyon, Rhynie, documented here under the label Rh2/301.2

* Annotation 2020: Incidentally, this contribution appeared nearly simultaneously with a more detailed publication on filamentous algae in the Rhynie chert [2]. That publication concerns a species which seems to be simlar to the present one.
Size data have been mistaken in [2], Fig.3: The cells in Fig.3a and b are seen in Fig.3e and k again but their alleged sizes differ by a factor of 4.
H.-J. Weiss      2019    2020

[1] David S. Edwards, A.G. Lyon:  Algae from the Rhynie Chert. Bot. J. Linnean Society 86(1983), 37-55.
[2] C.H. Wellmann, L.E. Graham, L.A. Lewis:
Filamentous green algae from the Early Devonian Rhynie chert. PalZ 93, 387–393 (2019).
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