Fish-like marine reptile buried in its own fat in southern Germany 150 million years ago

A new study published in PeerJ uses modern methods to understand the preservation of unique ichthyosaur fossils. A complete animal and a tail are the first to retain the outer body shape in the last major group of ichthyosaurs.

The new peer-reviewed paper describes two specimens of ichthyosaurs* from the Solnhofen region**, which are approximately 150 million years old. They are housed in the Jura-Museum, owned by Bishops Seminar Eichstätt. An ichthyosaur is a complete specimen, with the internal skeleton and an outline of the soft tissues around the body. The other is a full caudal fin. It is preserved along with the tail vertebrae and the soft tissues around it, confirming that ichthyosaurs also in this group had moon-shaped tails, like their ancestors.

The research was conducted by an interdisciplinary team of scientists. Lene Liebe Delsett, lead author, and Jørn Hurum worked with marine reptiles for several years at the Natural History Museum in Oslo, Norway. Martina Kölbl-Ebert is a specialist in the Solnhofen region and its fauna. They worked with mineralogist Henrik Friis, who analyzed the soft tissue samples to see what they contained.

“The complete specimen is really what makes this project unique because it tells a complete story. Ichthyosaurs are not common as fossils in Solnhofen, which at the time was a relatively shallow area with many islands, whereas ichthyosaurs were open ocean dwellers. We don’t. I don’t know why this one entered the lagoons, but that may be why it died. View specimen a an impact because it is obviously a complete dead animal body, where we can see its shape due to the unique preservation,” Delsett said. said.

During or after death, the ichthyosaur landed on its back and side on the seabed and was covered in fine sediment. Little oxygen and a lot of luck preserved it until it was discovered and excavated in 2009. In the article, the scientists give a first description of the specimen and begin the process of understanding its soft tissues. To do this, they took small samples of the soft tissues of the tail and examined them using X-ray crystallography and a scanning electron microscope. Because the skeletons and the rock in which they are preserved have almost the same color, UV light was used to study the shape of the bones in order to understand what type of ichthyosaur it is. They found that the phosphate found in the tissues of ichthyosaurs likely contributed to preservation. It is not yet possible to identify all types of fossilized tissue in the ichthyosaur, but the new study confidently confirms the preservation of skin and possibly connective tissue. However, most of the material surrounding and covering the specimen is probably decomposed fat.

“We know from previous research that ichthyosaurs probably had blubber, like whales have today. Our research confirms this, for one group of ichthyosaurs where it has not been certain. Fat is another strong similarity between whales and ichthyosaurs, in addition to their In the future, I hope that these two ichthyosaurs from Solnhofen can be used to improve our understanding of swimming, as they preserve the shape of the tail and the body”, says Delsett.

Remarks

*Ichthyosaurs were marine reptiles living in the age of the dinosaurs. Their fossils are found all over the world and they are famous for having a fish-like shape to today’s dolphins.

** The Solnhofen region in southern Germany is famous for its Late Jurassic fossils, which include Archeopteryx, generally recognized as the first bird, and many other animals, many of which are preserved with soft tissue in plus skeletons and teeth, which are rare in the fossil record.

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