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Fossil Weathering and Preparation Mimic Soft Tissues


in all anatomical parts of the specimen, including skeletal plates (Figure 1C), validates this hypothesis. Te somasteroid specimen shows a totally differ-


ent elemental distribution in the tube feet-like struc- tures, with the total absence of Fe and the presence of carbon. Carbonaceous films are the main mode of preservation of soſt tissues, especially in the Paleozoic era [26]. However, in surface sediments of the Fez- ouata Shale, carbon is absent from all fossils that have been analyzed [9,10,12]. Te porous aspect of C-rich deposits in the analyzed specimen is strikingly differ- ent from the texture of carbon films in exceptionally preserved biotas [26]. Moreover, in the somasteroid specimen, carbon is not limited to any specific region but appears to fill all micro-depressions of the speci- men (Figures 4D–G). Tus, it is very likely that this carbon is the consequence of preparation artifacts: numerous latex casts were made to study the detailed morphology of this specimen. Apparently, latex was not completely removed from small cavities located between skeletal plates, thus mimicking regularly branching tube feet along the ambulacral canal, in the arm region of the analyzed specimen.


Conclusion Tis study confirms the validity of the interpre-


Figure 2: SEM-EDX images showing amorphous shape of particles and iron-rich areas (white regions).


tation as soſt parts of the structures identified in sty- lophoran echinoderms from the Fezouata Shale [12]. However, it also shows that it is probable that reports


Figure 3: Analyzed specimen of somasteroid, late Tremadocian, Fezouata Shale, unknown locality, Zagora area, Morocco; UCBL-FSL424962. (A) Photograph of the specimen; (B) XRF, Si distribution; (C) XRF, superposition of Rh (blue) with K; (D) SEM-EDX elemental distribution in the tube feet-like structures.


2020 January • www.microscopy-today.com 27


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