Oribatid mite coprolites: Wishful thinking in science
deutsche Version

The alleged sightings of oribatid mite coprolites in palaeozoic wood, once a favourite subject of palaeobotanists worldwide, seem to have become rarer lately but still occur occasionally. It has been emphasized repeatedly that such sightings are brought about by superficial observation, poor judgement, and wishful thinking. One of the latest sightings of this kind concerns angular clots in Permian wood (Fig.1), presented as coprolites in [1].
angular clots, no coprolites cell-size clots in wood
Fig.1: Cell-size angular clots as they are occasionally seen in silicified poorly preserved wood. Detail of Fig.13 in [1], width of the picture 0.65mm.

Fig.2 (right): Cell-size angular clots in silicified wood with spots of damage, also a few cells with dark fill in intact tissue. Detail of Fig.15 in [1], width of the picture 0.4mm.

According to common sense, clots appearing as polygonal sections on the cut plane cannot be coprolites. It would not take vivid imagination to guess that they had been moulded after the lumina of cells, all the more so since virtually every petrified tree with clots shows some spot in the wood where the relation between clots and cells becomes obvious, as in Fig.2. A few clots are seen within not yet decayed cells above right, and the arrangement of the clots below left seems to be compatible with the tissue structure. As a possible explanation based on various observations, also on extant trees, the dark fill of some cells which finally leads to the destruction of the cell walls may be a type of wood rot [4]. There are a few cells in Fig.2 with small dark clots, apparently in a state of growth, which do not yet fill the cell.
Against all evidence the authors [1] and others assume that the damage to the wood as in Fig.2 had been done by gnawing oribatid mites although no such creature has ever been seen preserved together with the clots and the wood.
cell-size clots in wood
Fig.3: Permian wood from the same fossil site as those in Figs.1,2, with cell-size angular clots in the degraded half, arranged in deformed rows. Detail of Fig.17 in [2].

A tendency of lumps to stay there where they grew is indistinctly seen in Fig.3. This picture shows four features of the clots which make the coprolite interpretation seem absurd: cell-size and angular, in slightly deranged rows, and the number of clots per area roughly equalling the number of cells per area. This may be sufficient fossil evidence to justify the statement that to every alleged oribatid mite coprolite there had been a cell which produced it. This rule gets additional support by
clots orderly placed in rows of cells, as in Fig.4 and elsewhere.clots in cells
Fig.4: Clots growing in one cell each, having not yet filled the cell lumen. Detail from [3], Fig.4F, where they are offered as coprolites.

The arguments contradicting the coprolite interpretation are not new. They have repeatedly been presented to the authors [1] since 2007. R. Rößler replaced "oribatid mites" by "unknown creatures" in 2010 [2] and by "new detritivores" in 2012 [5] but revived the "oribatid mites" in 2014 [1]. Instead of engaging in discussion based on fossil evidence, sticking to the coprolites in palaeozoic wood is defended by referring to others who did the same. Those who have got into the same pitfall of misinterpretation reassure themselves by mutual benevolent referring so that it is virtually impossible to make them listen to arguments. In the present case they keep to the two simple features which fit into their simple concept: dark clots for coprolites, damage for boring galleries. They dismiss all features which do not fit in.
In the wood from the Crock fossil site (as well as in other fossil wood) there are cavities so narrow that no mite could have crept through but those are not mentioned in [1].
Every cavity made by mites should have an exit tunnel through which the mites had escaped before silicification set in since no mite has ever been found inside. However, no tunnels are seen on wood cross-sections, and borings along the tree trunk with several millimeters in length as mentioned in [1] p.61 could not have served as escape routes.  
Finally it can be stated that there were no coprolites and no mites in Permian wood, and all conclusions based on coprolites and mites in [1] and numerous other publications are not based at all.
For more examples of coprolite publications refuted see "Wood rot or coprolites".

H.-J. Weiss     2015

[1]  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.
[2]   M. Barthel, M. Krings, R. Rößler: Die schwarzen Psaronien von Manebach, ihre Epiphyten, Parasiten und Pilze. Semana 25(2010), 41-60.
[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]  F. Schwarze: Fungal strategies of wood decay in trees. Springer, Berlin 2004.
[5]  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. 
quartz crystal with wood inside
Fossil Wood News  23

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