Permian tree fern details
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maggot fern pinnules10
Tree fern foliage and stems make a major part of the fossils in the Permian cherts found in the Doehlen basin, Germany. As a lucky coincidence, pinnules of the big fronds appear on a small area of a cut face of a sample with various orientation: Fig.1. Above right there is a pinna cross-section with two pinnules cut lengthwise. The tilted cut of the four 0.13mm-wide pinnules below left makes them appear thicker than they really are. Another pinnule is cut such that its veins are clearly seen. Their angle of about 45° with respect to the midrib immediately leads to the dispute [1] concerning the tree fern species in the Doehlen basin.

Fig.1: "Maggot fern" pinnules with various orientation. Image width 10mm.

As discussed earlier [1], the repeatedly questioned claim that there is only one tree fern species in the cherts of the Doehlen basin [2], Scolecopteris elegans known as "maggot fern", cannot be upheld. Lately it has appeared that some of the tree fern pinnules in chert offered as Sc. elegans including even one alleged type specimen [3], represent one ore more other species [4]. This newly arising uncertainty concerning the "maggot fern" is one of the reasons why this new contribution on an old species seemingly well known since the early days of paleobotany may be justified.

Fig.2 (below): "Maggot fern" pinna cross-sections with pinnules cut lengthwise.
Note the sharp contour of the midrib of the above pinna. Image width 10.5mm.

maggot fern pinnules
The confusion still prevailing in the scientific literature concerning the "maggot fern" Scolecopteris elegans, also known as Pecopteris arborescens [5] or Scolecopteris arborescens [5] is due to various reasons. One of them is the fact that the pinnule veins are seldom seen as clearly as in Fig.1 and in [1]. Even among the thousand pinnules on the magnificient image of the biggest "maggot stone" ever found there is not one with clearly seen veins [2].

Aligned epidermis cells had been mistaken for a dense cover of hairs on the upper side of the pinnules ([5], p.280 and Tafel VIII Bild 7) but this had been retracted later by the author himself.
Scattered hairs may be present on the lower side of the pinnule, as seen below right in Fig.2. They are easily confused with fungus hyphae but are recognized as hairs by their attachment to the pinnule. For a clearer distinction of hyphae and hairs see [6].
In view of the largely decayed tissue of the pinnules, the uncommonly distinct contour of the midrib cross-section of the above pinna in Fig.2 is enigmatic.
Fused sporangia, known as synangia, are not seen on cut faces here. As a lucky coincidence, a slightly inclined cross-section of a pinna on the raw surface of this sample (Fig.3) provides a sideways view of a pinnule with a row of fringes seen from outside and synangia hidden behind. Also it provides a lengthwise section of the left pinnule with synangia.

With suitable position and orientation of the cut plane, the fringes on the pinnule margins can be conspicuous on pinnule cross-sections<. (See, for example, the logo at the bottom of this page.) 
maggot fern pinnules
Fig.3: Slightly inclined cross-section of a pinna on the raw surface of this sample, with fringes or lobes on the edge of the right pinnule. Width of the image 8mm.

This small sample (0.3kg) with "maggot fern" is distinguished among hundreds of others found in the Döhlen basin not only by providing several details as seen in Figs.1-3 but also by being the only one ever found near Pesterwitz. Repeated thorough search on agricultural areas near Pesterwitz produced 14 mostly small samples of petrified wood, among them a unique one , not yet identified, and a tree fern stem fragment of the Psaronius type (Fig.4). Since the "maggot fern" stems are of the same type, Fig.4 may serve as an illustratory addition to Figs.1-3.Psaronius aerial root

Fig.4: Psaronius aerial roots with "star-shaped" cross-sections of the central strand: with dainty cell walls (right), or squeezed and stained red with hematite (left),
on the raw surface of a small sample of 41g. Image width 7mm.

Psaronius aerial roots preserved in chert are mostly seen in a more or less squeezed state.
Hence, the well preserved central strand in this sample, with clearly seen thin walls of big cells, is remarkable.
Samples found near Pesterwitz, Doehlen basin; Figs.1-3: Pe/3 (1994); Fig.4: Pe/10 (1995).

H.-J. Weiss     2020

[1]  Permian Chert News 2 , Venation pattern ...
[2]  M. Barthel: Die Madensteine vom Windberg, Deutschland.
        in: U.
Dernbach, W.D. Tidwell: Geheimnisse versteinerter Pflanzen. D'ORO Verlag, Heppenheim 2002, p65-77.
[3]  M. Barthel: Die Rotliegend-Flora der Döhlen-Formation. Geologica Saxonica 61(2) (2015), 108-229.
[4]  Permian Chert News 26  ,  
Maggot fern confusion.
[5]  M. Barthel: Pecopteris-Arten v. Schloiheims aus Typuslokalitäten in der DDR.
        Schriftenr. geolog. Wiss. - Berlin 16 (1980), 275-304.
[6]  Permian Chert News 17 ,  Microbes, fungi, maggot fern.
Scolecopteris pinnule cross-section, Sardinia Permian Chert News30
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