Palaeozoic mites that never existed

deutsche Version

Like unicorns and mermaids in fairy tales, oribatid mites enjoy a virtual existence in palaeobotany, where they are supposed to have gnawed through palaeozoic wood all over the world. A considerable number of scientific publications has been devoted to them but their reputation seems to have declined lately, except for two recent papers promoted by R. Rößler and Z. Feng [1,2].
A serious problem with the subject has been formulated in [2]: "No evidence of body fossils was found in the specimen, although tunnel geometry and coprolite dimension suggest that oribatid mites were the most probable culprit." The absence of body fossils in the specimen in [2] might be considered incidental if there were not the fact that body fossils were never found in any palaeozoic wood allegedly inhabited by oribatid mites. Furthermore, not only body fossils are absent but moults, too, although it is known from palaeozoic arachnids that fossil moults are found more often than fossil bodies.
There is a simple solution to the serious problem in [1,2] and every other publication on the subject: There were no mites. Only one picture from [2] is sufficient to provide evidence for this supposition: 
Fig.1: Permian wood with local damage and peculiar arrangement of cell-size dark clots generally thought to be oribatid mite coprolites.
Detail of Fig.1C in [2]. Width of the picture 1.2mm.
Very similar: Fig.2D in [2].

Close inspection of Fig.1 reveals details of the arrangement of the dark clots which are incompatible with the interpretation as coprolites. At the bottom of the angular cavity in the wood there are

. Earlier stages of clot growth are seen elsewhere, as in two neighbouring cells left of the cavity. All these details justify a conclusion already formulated in a comment on [1]:
To every alleged oribatid mite coprolite there had been a cell which produced it. There is lots of additional evidence for this in silicified wood samples and even in the very pictures published by those who claim to see coprolites. If inspected thoroughly, their pictures always reveal a few clot sections with one or more straight contour lines meeting at an angle which marks an edge of the clot: Fig.2.

Fig.2: Cell-size clots, partially with distinct angles and straight contour lines which are incompatible with the usual interpretation as coprolites. Detail of Fig.1C in [2]. Width of the picture 0.3mm.

The sections of the clots do not aways appear as polygons, for several reasons: The clots may not have been moulded after the cell cross-sections, the cells may have been rounded inside, or the cut plane may be oriented such that it mainly shows the rounded ends of the clots. The authors fond of the mites do not notice the angular clots but see only the rounded ones, calling them "ovoidal to sub-spheroidal coprolites" [2]. Similar misjudgement is common with related publications.
The lack of thoroughness is particularly obvious in connection with Figs.3,4 where the authors ignore the straight sides and distinct angles and

Fig.3: Damaged Permian wood with angular clots whose sizes and shapes are compatible with those of nearby cells but nevertheless are regarded as coprolites in [3]. Detail from Fig.3I in [3], bar = 0.2mm.


Fig.4 (left): Angular clots of various sizes and shapes fitting to the various cells of nearby tissue of the Permian coniferous tree Plyophyllioxylon, interpreted in [4] as "spheroidal or ovoid shaped" coprolites. 
Drawing after detail from Fig.3C in [4].


The assumption

Annotation 2016: At least,  R. Rößler seems to give up trying to make believe that the absurd hypothesis of oribatid mite coprolites is valid. Recently M. Krings has shown that the alleged coprolites in a paper by Barthel, Krings, Rößler (2010) are no such but tangles of fungus hyphae as already proposed in Fossil Wood News 4 in 2011.

24