Plant fossils are extremely rare in the Muschelkalk, because plant fragments can only drift some 10s of kilometres before they are soaked with water and finally sink to the sea floor. And, preservation conditions for plant matter are generally bad in limestones. Therefore, I regard my finding of a plant fragment that's possibly a part of arge marine algae as very unusual.
In Keuper sediments, plant fossils are far more common. Fluvial systems reached further and further into the Germanic Basin and carried plant fragments to the peripheral marine areas. Occassionally draining lakes and swamps formed on the delta tops, with an individual-rich flora that is now preserved in sandstones. Root beds mark the original location of the plant associations. Especially the Lettenkeuper Hauptsandstein, the Schilfsandstein (the name derives from abundant horsetail fossils) and the Stubensandstein are rich in plant fossils. Charred tiny plant fragments are quite abundant in mudstones and wackestones of brackish origin in the Lower Keuper. They usually show an adjustement to the current direction. Locally, accumulation of organic matter of plant origin led to the formation of - small and useless - coal deposits.
In general, plant remains are mostly found as a thin, compacted layer of coal, as a steinkern (sedimentary infill of cavities, esp. with horsetails) or permineralized (Quartz, goethite, pyrite).
Quite famous are the large petrified conifer logs from the Stubensandstein of the Löwensteiner Berge (Löwenstein Mountains) that can reach lengths of several metres.
unidentified
This certain plant fragment shows no strcutures - apart from regularly arranged cavities within the partially exposed inside (lower picture). The lack of any structures that could be related to a supporting or vascular tissue gives me reason for an interpretation as a part of a large marine algae.
Upper Muschelkalk (Trigonodus-Dolomit), Bietigheim-Bissingen
Danaeopsis arenacea
Lower Keuper (Hauptsandstein), Sulz am Neckar
Equisetites arenaceus JAEGER
Lower Keuper (Hauptsandstein), Bretzfeld
Neocalamites merianii (BROGNIART)
Steinkern made up of goethite
Lower Keuper (Hauptsandstein), Ilsfeld
Schizoneura paradoxa SCHIMPER
Lower Keuper (Hauptsandstein), Rielingshausen
Swedenborgia sp.
Female cone in cross section.
Lower Keuper (Hauptsandstein), Rielingshausen
Cone of a cordait
Lower Keuper (Hauptsandstein), Rielingshausen
Dadoxylon keuperianum
Round log fragment, permineralized by quartz and goethite.
Middle Keuper (Stubensandstein), Wüstenrot
Radicites sp.
Vertikal section through a root bed.
Middle Keuper (Stubensandstein), Wüstenrot
(Scale length: 10 cm)