As mentioned, the Urweltmuseum Hauff has a large section showing the rock layers and their fossil content as a “rock staircase”.
Right at the top it begins with an impressive display of ammonites from the “Wilder Schiefer” III (“wild shale”), so called because its bedding is irregular in the upper part. These shells were carried together by currents, and are not just an accumulation of animals living and dying at (nearly) the same time in the water above.
and here is a closer view of one of the two layers in the Wilder Schiefer III that contain such mass burials, of Harpoceras falciferum (the big one) and Dactylioceras commune.
Let’s talk a bit about the stratigraphy of the Posidonia Shale. Over the years several different schemes have been developed, some of which work very well locally, others work better on a larger scale. And there are the old stonemason’s terms, too. Wilder Schiefer is one of them. I found a nice comparison in the Doctoral Thesis of one Andreas Frimmel from Tübingen – I have a vague memory of what he looks like, so I’d recognize him at a conference. Us Tübingen geosciences guys are everywhere in German palaeontology and geology 👿
Here’s Fig. 3 (pars) from Frimmel, showing the modern biostratigraphy compared to the lithostratigraphy by Quenstedt and by Hauff (Hauff’s is the one with the Roman numerals, whereas Quenstedt used all the stonemason’s names), and a classification of the facies. As you can see the Lias ε coincides nicely with the lower Toarcian, and the ammonite genera Hildoceras, Harpoceras and Dactylioceras are in fact the most common fossils in the Posidonia Shale by far.
On with the photos – here are the most commonly found ammonites, of which the Urweltmuseum has a very nice display:
Phylloceras heterophyylum (Sowerby), found in Lias ε II3-III. These ammonites grew quite large, with diameters of 50 or 60 cm not uncommon. The shell’s outside was structured with thin ribs and big, knobby secondary ribs extending only over the inner third or so. No keel on the outside and a very involute curl mean that the shells often fractured with shards spread around a bit.
Eleganticeras elegantulum (Young & Bird) – I think it is quite self-evident how this one from the Lias ε II4 got its name.
Side by side, the two Lias ε III beauties with keel (and thus near-perfect spiral preservation, as is the case for Eleganticeras above): Harpoceras falcifer and Hildoceras sublevisoni.
And finally, here we go with Dactylioceras – the species epithet is commune.’ Nuff said.
This one has two shells growing on it, Gervillia lanceolata and Inoceramus dubius. Typical, however, are find like the one below:
the final member of the family of most common ammonites is Lytoceras, but I will now not show you the abundant species L. simensi (Denkmann), but one that brings along a vertebrate for the ride: L. ceratophagum Quenstedt, with Dapedium pholidotum in the living chamber. The two slabs are mounted side by side in the museum, and always have me wondering just how much luck some people have splitting the rocks!
as always, click pics for bigger version, and yell for full size uncropped images in comments!
Next post will have more stuff from the “rock stair”, then we get to the really really cool stuff and some more life models of Lias animals.
Frimmel, A. 2003. Hochauflösende Untersuchungen von Biomarkern an epikontinentalen Schwarzschiefern des Unteren Toarciums (Posidonienschiefer, Lias ε) von SW-Deutschland. Doctoral Thesis, Eberhard-Karls-Universität Tübingen.