Wood rot or coprolites ?
deutsche Version

Evidence for live and dead plants being attacked and partially consumed by fungi or small creatures is found as far back in time as the Lower Devonian. If not preserved in chert or, in later times, in fossil wood, such evidence is hard or virtually impossible to find. This may explain why the examples presented here cover only the Rhynie chert plants and silicified wood from a few locations but not the vast majority of plants preserved as compression fossils. Asteroxylon cells with dark fill

Fig.1: Asteroxylon in Rhynie chert, tissue mostly destroyed by fungus activity (above left), detail of cross-section: individual cells filled with dark matter, thus remaining clearly visible while the empty cells are no more seen.

For Rhynie chert plants affected by fungi and unknown creatures see:
Rhynie Chert News 4, 21     fungus-induced growth anomaly
Rhynie Chert News 7          spore eaters
Rhynie Chert News 28        cell-size
clots 
Rhynie Chert News 37        arthropod borings
Rhynie Chert News 85        cell-size clots 

As a conspicuous phenomenon persisting through the ages from the Lower Devonian to present times, cell-size clots similar to those in Figs.1,2 are often present in wood, usually at or near spots of damaged tissue. The clots are seen inside cells as well as scattered around where the tissue is decayed. Clots filling the wood cells of extant trees are produced by several fungi [1], as Acanthophysium sparsum, for example. Psaronius aerial root phloem cells empty or with dark fill

Fig.2: Psaronius aerial root phloem cell with dark fill surrounded by empty cells. Detail from [4], Fig.8, there erroneously denoted as aerenchyma instead of phloem. (Note also the typical shape of a collapsed cell below the filled cell, as it is often seen in slightly compressed wood.) The dark fills have been interpreted as
coprolites in [4].  (See no coprolites .)   silicified wood cells with dark fill: alleged coprolites

Fig.3 (right): Permian wood, alleged frass gallery with coprolites according to [4], Detail from [4], Fig.17. What is really seen here is deformed wood with part of the cells filled with dark matter but neither coprolites nor gallery. Note the angular shapes of some of the clots, the kinked pith ray with dark fill, and the small clot in a large cell nearby. 

It seems incomprehensible why palaeobotanists did not consider fungus or microbial activity as possible explanations of the clots but brought up the idea of oribatid mite coprolites without any oribatid mite at hand throughout the Carboniferous, Permian, and Triassic. Apparently the mite coprolite idea spread in the 1990s by adopting without checking but by following the hearsay principle, with the result that there are a number of dubious papers on alleged mite coprolites in scientific journals and books.
Instead of engaging in discussion based on fossil evidence, those promoting the idea of mite coprolites in palaeozoic wood from all over the world defend this idea by referring to those who do the same.
Despite of warnings against the coprolite hypothesis since 2007 [2], more publications on the subject appeared [3,4]. The publication [4] abandoned the oribatid mites but introduced unknown creatures, which is still a long way off the truth that there were neither mites nor other creatures involved. 

Alleged coprolites refuted :
Fossil Wood News 3, 4        Permian wood from Germany
Fossil Wood News 5            Permian wood from Northern China
Fossil Wood News 6            PsaroniusAnkyropteris, Permian, Chemnitz, Germany
Fossil Wood News 7           Carboniferous coal balls, Permian wood and ferns

Fossil Wood News 8           Permian wood from Germany and Northern China
Fossil Wood News 11         Triassic fern and wood from Antarctica
Fossil Wood News
12            Ankyropteris, Permian, Chemnitz, Germany
Silesian Petrified Wood       silicified wood from Poland
Fossil Wood News 14
           alleged borings
Fossil Wood News 16            wood with light-coloured clots
Fossil Wood News 18            Triassic bennettitalean roots, Cretaceous bennettitalean stem
Fossil Wood News 20         Plyophyllioxylon, Permian, China
Fossil Wood News 21           Palaeozoic wood, Kyffhäuser mountains, Germany
Fossil Wood News 22         Australoxylon, glossopterid wood from Antarctica
Fossil Wood News 23          Permian wood from Thuringia, Germany 
Fossil Wood News 24          Permian wood from Thuringia, Germany
Fossil Wood News 26          Permian wood from Schallodenbach, Rhine-Palatinate, Germany  

H.-J. Weiss    2011,      emended 2013, 2014, 2015, 2016

Annotation 2013, 2014:
As it appears now, the controversy of "wood rot versus coprolites" has provided the proof that lay palaebotany on the Web can affect professional palaeobotany despite of the claims by professionals that one must not trust anything that has not undergone a reviewing process and has not been printed. The fact that lots of errors and misconceptions have entered into the scientific literature is readily ignored by those who adhere to such view.
The own effort to refute the mite coprolite interpretation of cell-size clots in palaeozoic and mesozoic plant tissue, from 2007 on [2], has given rise to differential response, ranging from tacit acceptance of the alternative view to desperate defense of the repeatedly published one [3,4]. The effort has not been in vain: From 2011 on, those who got in touch with the present website seem to have abandoned the once favourite subject of oribatid mite coprolites. Some uncertainty of the authors [6] is apparent from formulations like "the coprolites described here ... may also indicate the activity of ancient oribatid mites" and "the coprolites ... are interpreted to represent a new detritivore."
Some former proponents of the mite coprolite hypothesis have been lucky to find coprolites after all, a million times bigger than cell size in volume, which they assign to bigger arthropods [5].
It does not seem incidental that erroneous views in publications are often found in combination with lack of thoroughness. Apparently there is a causal connection, for which [7,8] provide lots of examples. Along with numerous mistaken size data, R. Rößler presents coprolites, arthropod burrows, and fossil charcoal which are no such (see Fossil Wood News 16, 9).
Since erroneous views are virtually never retracted in writing and hence have to be opposed by other means, the sections "Misconceptions" and "Errors and Mistakes" have been set up on this website.
Annotation 2015:
As a setback in the attempt to weed out the ill-conceived concept of mite coprolites in connection with cell-size clots in petrified wood, two more publications on the subject have appeared in 2014 and 2015 [9,10]. By looking closely at the images shown there it becomes obvious that they are likewise erronous as others before, as explained in Fossil Wood News 23 , 24.
Annotation 2016: pale clots in wood cells
It has been noticed only now that one sample from the own collection which has provided evidence against the coprolite interpretation before can also provide evidence of clot formation inside cells, beginning with a pale clot which may or may not become darker and cause the decay of the cell wall: Fossil Wood News 26. Considering the new evidence and the own efforts since 2007 to refute the worldwide accepted mite coprolite hypothesis, it may be appropriate to confront the proponents of that hypothesis with the slogan "The end is near". Perhaps people at the Naturkunde-Museum Chemnitz have heeded the advice given to them and have begun to wonder why never a fossil mite fitting to the alleged coprolites was seen. This could explain why the latest publication on the Rotliegend of Chemnitz [11] does not mention any more the hitherto cherished fantasies of oribatid mites, these "fossil gourmets" ([7], p.169).

[1] F. Schwarze: Fungal strategies of wood decay in trees. Springer, Berlin 2004.
[2] H.-J. Weiss, Rätselhaftes aus Hornstein und Kieselholz. 6. Chert Workshop 2007, Naturkunde-Museum Chemnitz.
[3] 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.
[4] M. Barthel, M. Krings, R. Rößler:   Die schwarzen Psaronien von Manebach, ihre Epiphyten, Parasiten und Pilze.
     Semana 25(2010), 41-60.
[5] R. Rößler, Z. Feng, R. Noll: The largest calamite ... . Rev. Palaeobot. Palyn. 185(2012), 64-78.
[6] Zhuo Feng, Jun Wang, Lu-Yun Liu, R. Rößler:  A novel coniferous tree trunk with septate pith ...
     Int. J. Plant Sci. 173(2012), 835–848. 
[7] R. Rößler: Der versteinerte Wald von Chemnitz. Museum f. Naturkunde Chemnitz 2001
[8] B. Slater,  S. McLoughlin, J. Hilton:  Animal–plant interactions in a Middle Permian permineralised peat ..., Prince Charles Mountains, Antarctica.
      Palaeogeogr. Pal. Pal. 363-364 (2012), 109-126.
[9] R. Rößler, R. Kretzschmar, Z. Feng, R. Noll: Fraßgalerien von Mikroarthropoden in Konifernhölzern des frühen Perms von Crock, Thüringen.
       Veröff. Mus. Naturkunde Chemnitz 37(2014), 55-66.
[10] Zhuo Feng, J.W. Schneider, C.C. Labandeira, R. Kretzschmar, R. Rößler:  A specialized feeding habit of Early Permian oribatid mites.
       Palaeogeography, Palaeoclimatology, Palaeoecology 417(2015), 121-124.
[11] L. Luthardt, R. Rößler, J.W. Schneider: Palaeoclimatic and size-specific conditions in the early Permian fossil forest of  Chemnitz ...
       Palaeogeography, Palaeoclimatology, Palaeoecology 441(2016), 627-652.

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