Maggot ferns from Sardinia and Saxony - surprisingly similar and different
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Permian tree ferns with big fronds whose small pinnules known as Scolecopteris found world-wide well-preserved in chert are usually sorted into about two dozen species [1]. One of them, found in chert on Sardinia, looks rather similar to Scolecopteris elegans (Figs.1,2), first discovered in Saxony in 18th century, first scientifically described in 1837 [2] and 1874 [3], and questionably described anew by means of three allegedly typical samples in 2016 [4]. A more careful look at the three selected samples reveals that they have been ill-chosen for the present purpose as they clearly show features of two different species, thus causing confusion instead of defining the true Sc. elegans.
As a distinct feature of Sc. elegans, the pedicels bearing the synangia are much shorter than wide (Fig.1) and hence their position and orientation to the cut plane is seldom incidentally such that they are readily seen as in Figs.1-3, which have been selected from a large number of pictures.

pinnule10pinnules Fig.1 (far left): Scolecopteris elegans  pinnule cross-section with the seldom seen pedicels bearing the synangia, drawn after the lectotype in [5]. Image width 2mm.
Sc. section closely resembling the lectotype. Image width 2mm.
Fig.3: Sc. sections, pedicel seen on the right. Image width 4.3mm.

Complications arise from the fact that one characteristic feature of Sc. elegans, the narrow gap between the sporangia and the pinnule, which appears dark in Fig.2 and pale on the far right in Fig.3, is seen on some other species, too. In cases where other distinctive features are not available, the fossil cannot be assigned to an established species. This applies to Fig.3, which has been taken from a sample presented in Permian Chert News 1, there Fig.7, whose venation pattern differs from that of  Sc. elegans.
By comparing Figs.1-3 with
Figs.4-6, one may arrive at the conclusion that the similarities outweigh the differences. Hence, the "maggot fern" from Sardinia is similar to two (or more ?) species from Saxony. With such state of things one could be satisfied if there were not the confusing claim in [4], p. 226, that the sample
Bu8/18 (with big pedicels) be representative of Sc. elegans. Apparently the author had overlooked the big pedicels bearing the synangia.

synangia in a row

Figs.4,5: Scolecopteris pinnule cross-sections on the raw surface of a chert fragment found at Perdasdefogu. Image width 2mm.
Fig.6: Same
sample as Figs.4,5, row of synangia . Image width 2mm.synangium

Fig.7(right): Scolecopteris pinnule half with one synangium on a big pedicel, with spores inside the two sporangia seen here on a cut face; disputed specimen from Saxony. Image width 1.5mm.

Note that Figs.4-6 show the raw surface while
Figs.1-3,7 have been taken from cut faces.

Lots of chert samples with Scolecopteris recovered in the 1990s have been stored away and not even looked at. Hence it is well possible that more surprises will be found when the samples are thoroughly investigated.
So it turns out that the surprising difference mentioned above is not due to the different locations but to distinctly different features of two species from the same location, the maggot stone site in the Doehlen basin in Saxony. The difference becomes obvious by comparing the two images in Permian Chert News 34.
Samples from Doehlen basin: Fig.2: Bu7/89 (4.69kg) Part2, found by Schiefner in 2000;  Fig.3: H2/35 Part1, found near Haenichen in 1993;  
Bu8/18, found by Ulrich Wagner (Dresden) at Freital-Burgk in 1997;
Samples from Sardinia
: Figs.4,5,6: Pd/2.1, found near Perdasdefogu in 2009.

H.-J. Weiss    2021

[1]  M.A. Millay: A review of permineralized Euramerican Carboniferous tree ferns. Rev. Palaeobot. Palyn. 95(1997), 191-209.
[2]  E. Zenker: Scolecopteris elegans, ein neues fossiles Farrngewächs mit Fructification. Linnaea 11(1837), 509-12.
[3]  E. 
Strasburger: Über Scolecopteris elegans ..., Jenaische Z. Nat. N.F.1 Jena 8(1874), 81-95.
[4]  M.
Barthel: Die Rotliegendflora der Döhlen-Formation. Geologica Saxonica 61 (2) (2015, released in 2016), 105-238.
[5]  M. Barthel, W. Reichel, H.-J. Weiss:  "Madensteine" in Sachsen.  Abhandl. Staatl. Mus. Mineral. Geol. Dresden 41(1995), 117-135, Table 1.

Scolecopteris pinnule cross-section, Sardinia Permian Chert News 35
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