Jurassic plesiosaurs are well known... would you think! But there are actually some gaps in our knowledge which are still hard to fill.
So it was a pleasant surprise when Sven Sachs learned of a plesiosaur specimen in the hands of Siegfried Schubert which came from the Pliensbachian, one of these gaps.
How it turned out this specimen, which was handed around non-plesiosaur experts for some time, was among the three most complete specimens of this stage. And how further investigations showed it was also a new genus.
Yesterday it was published and also shown to the press. Arminisaurus is the name of this new beast, which wasn't completely fully grown when it died but probably hit up to 3,5 m in length.
Besides it's welcoming stratigraphic placement it also shows a strange character combination. Some features of this beasts are only found in Cretaceous taxa, which opens the question how much evolutionary importance some of these characters have, and which are just convergent functional developments.
Phylogenetic analysis placed Arminisaurus near the base of the pliosauromorph clade, however this could change in the future because Arminisaurus is in a way different that it could point to a hidden diversity among early pliosaurians, I wouldn't surprised if we would have one day Ariminisauridae as a own clade. But that's just musings in the moment, the pliensbachian gap is still one that has to be filled, and I'm excited to see what the future will show us.
For this picture I looked into the literature of this formation, especially the "Herforder Liasgrube", the broader locality were this fossil comes from. Unfortunately this part of the formation is still underrepresented in the literature, so I based parts of my picture on the Franconian part.
Fish are rather rare, but cephalopods, especially belemnites are a common find, as well as ammonites, clams and brachiopods. Terrestrial fossils are nearly unknown, only fossilized wood shows that the land was probably not that far.
Because Arminisaurus has short robust teeth I depict it here with a suitable prey item: Eryma, a crustacean which was common during the Jurassic in Germany. It probably also ate fish and belemnites, and how Siegfried told me there are ammonites with probably suitable bite marks.
I also need to thank Sönke Simonsen another local collector who was so kind to help me a little with the faunal composition.
Here the paper:
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