Alleged coprolites of "unknown creatures" replace alleged oribatid mite coprolites
deutsche Version
After the row about oribatid mite coprolites in Palaeozoic plant fossils had calmed in the latter years, the attention paid to the subject has unexpectedly increased again. It started in 2010 with a paper by
Zhuo Feng et al. [1], recognized and described as erroneous in [2]. (See also Misconceptions.)
As a novelty, in a publication by
M. Barthel, M. Krings, R. Rößler [3] the dark granules are no more assigned to the favourite oribatid mites as done before in several papers by various authors (see compilation in [4]) but to "unknown creatures". The reader is also told that fungi are closer related to animals than to plants. Is this intended to pave the way for a recognition of the little clots as fungus formations ? This would be a too optimistic interpretation. It will rather take some effort to remove the absurd notion of coprolites of small plant eaters whose shapes and sizes, including edges and angles, agree with those of the cells eaten. No effort is needed to convince average people but this is different with the palaeobotanists who promoted the mite coprolite hypothesis. Therefore, the old arguments have to be applied here to the new pictures.
Angular clots misinterpreted as coprolites
Fig.1: Part of Fig.16 in [3], there interpreted as "coprolites in the conducting tissue (scalariform tracheids) of a Psaronius root", here interpreted differently. (*)
According to experience, small clots of this kind agree with the cells of the "eaten" plant tissue with respect to shape, size, and variability.

Contrary to the assertion in [3], no clot is seen inside the tracheids. All of them are lying around outside. They are angular like the cells of the decayed tissue whose remains are seen in the corner below left. As in numerous similar cases, they can easily be interpreted as fills of cells whose walls have gone. In this connection, the next picture is revealing.
Clots in silicified wood misinterpreted as coprolites

Fig.2 (right): Detail from Fig.17 in [3],
there interpreted as "Dadoxylon sp cross-section of secondary xylem with coprolites within a gallery", here interpreted differently. (*)

Where is a gallery in this picture ? No such is seen but there are other things worth being noticed: individual dark clots inside cells, chains of dark clots, and narrow dark pith rays. There is a pith ray with dark fill, kinked into a conspicuous Z-shape.
These observations are compatible with the notion of something propagating from cell to cell, or also to more distant cells, to produce dark fills. Such phenomenon is known from the fungus Glomites rhyniensis: [6] Fig.3.47. It enters into the cell, branches
 profusely to form a tangle of very thin hyphae, filling the cell more or less completely and looking like a dark clot, then penetrating the wall to get into the neighbouring cell to branch there, and so on. (See picture below.)  Formation of fungus clots within plant cells

Fig.3: Picture from [5] Fig.19 and [6] Fig.3.96: Dark clots consisting of a tangle of very thin hyphae of Glomites in cells of Aglaophyton from the Lower Devonian Rhynie chert. Note the hypha penetrating the wall.

To sum up, one can state that the alleged coprolites are neither related to oribatid mites nor to unknown creatures but are no such at all, same as in numerous other cases of small dark clots in silicified plants.
* The misinterpretation in [3] was noticed by Gert Müller (Dresden).
   For more critical annotations to [3] see "Wood rot" and "Remnants".

H.-J. Weiss         Dec. 2010

[1]  Zhuo Feng, Jun Wang, Lu-Yun Liu :
      First report of oribatid mite (arthropod) borings and coprolites in Permian woods from the Helan Mountains of northern China.
      Palaeogeography, Palaeoclimatology, Palaeoecology 288(2010), 54-61.
[2]   H.-J. Weiss: Dubious oribatid mite coprolites once more: Comment on Z. Feng et al. (2010),
[3]   M. Barthel, M. Krings, R. Rößler: Die schwarzen Psaronien von Manebach, ihre Epiphyten, Parasiten und Pilze. Semana 25(2010), 41-60.
[4]  H.-J. Weiss: Oribatid mite coprolite sightings – a transient craze ?
[5]  H. Kerp: De Onder-Devonische Rhynie Chert ... . Grondboor & Hamer 58(2004), 33-50.
[6]  T.N. Taylor, E.L. Taylor, M. Krings : Paleobotany, Elsevier 2009.

Annotation (2011):
The authors [3] were not interested in discussing the problem.
A critical comment on [3] (in German) suitable for publication in the journal "Semana" has been rejected on grounds of pretended copyright violation.

Annotation (Sept. 2016): Years of continuing own effort to unsettle the proponents of the coprolite interpretation of clots in petrified wood have not been in vain. Finally they accepted the fungus interpretation proposed above: Another investigation [7] revealed the presence of several different fungi in
the very same Psaronius specimen as in [3]. Even hyphae penetrating the cell wall of another plant for a substitute as shown in Fig.3 have been found with this Psaronius specimen. Unfortunately, this laudable change of mind of two of the authors [3,7] comes along with the reluctance to admit errors. The conspicuous cell-size clots erroneously offered as coprolites in [3] are not mentioned at all in [7]. Hence this error, like several others in palaeobotany, has to be addressed expressly.
    

[7]  M. Krings, T.N. Taylor, C.J. Harper, M. Barthel: Endophytic fungi in a Psaronius root mantle from the Rotliegend of Thuringia, Germany.
       87th Annual Conference Paläontologische Gesellschaft, Dresden, Sept. 11-15, 2016.
quartz crystal with wood inside
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