Fish resembling marine reptile from 150 million years ago uniquely discovered in Germany

New Delhi: An international team of researchers are using modern methods to understand the preservation of unique ichthyosaur fossils.

Ichthyosaurs, meaning “lizard fish” in ancient Greek, are large, extinct marine reptiles. They are distant relatives of lizards and snakes and were the most specialized aquatic reptiles. Their fossil remains span almost the entire Mesozoic era (251 million to 65.5 million years ago).

Ichthyosaurs lived in the age of dinosaurs and their fossils are found all over the world. These marine reptiles are famous for having a fish-like shape resembling today’s dolphins.

Study describes two new ichthyosaur specimens

Scientists have described two new ichthyosaur specimens, which are the first to retain the outer body shape in the last major group of ichthyosaurs. One of the specimens is that of the complete animal, while the other specimen is that of the tail of an ichthyosaur. These specimens are about 150 million years old.

The peer-reviewed article describing ichthyosaurs was recently published in the journal PeerJ.

Several Late Jurassic fossils are found in the Solnhofen region of southern Germany. These include Archeopteryx, which is generally recognized as the first bird, and various other animals. Many of these animals are preserved in soft tissue in addition to skeletons and teeth, which is rare in the fossil record.

Where were the specimens found?

Two ichthyosaur specimens from the Solnhofen area, around 150 million years old, were described in the study.

The specimens are kept in the Jura-Museum, located in Willibaldsburg Castle in the town of Eichstätt, Germany.

Characteristics of Ichthyosaurs

According to the study, an ichthyosaur is a complete specimen, with the internal skeleton and an outline of the soft tissues around the body perfectly preserved.

The other specimen is a complete caudal fin and is preserved with caudal vertebrae and soft tissue around it. This confirms that ichthyosaurs in this group also had moon-shaped tails, like their ancestors, according to the study.

The researchers analyzed the soft tissue samples to see what they contained.

Study results

In a statement released by PeerJ, Lene Liebe Delsett, the study’s lead author, said the complete specimen is really what makes this project unique because it tells a complete story. She explained that ichthyosaurs are not common as fossils in Solnhofen, which at the time was a relatively shallow area with many islands, whereas ichthyosaurs were inhabitants of the open ocean.

She said researchers don’t know why this ichthyosaur entered the lagoons, but that could be why it died.

She added that seeing the specimen is impactful as it is clearly a complete dead animal body, where its shape can be seen due to its unique preservation.

According to the study, the ichthyosaur, during or after its death, landed on its back and side on the seabed, and was covered in fine sediment. It was preserved with a little oxygen until it was discovered and excavated in 2009.

Understanding Soft Tissue Using X-ray Crystallography

The researchers made an initial description of the specimen in the article. In order to understand the soft tissues, the scientists took small samples of the soft tissues from the tail and examined them using X-ray crystallography and a scanning electron microscope. X-ray crystallography is a tool used to determine the atomic and molecular structure of a crystal. Crystalline atoms cause an X-ray beam to diffract in many specific directions.

A scanning electron microscope is an instrument that produces a greatly magnified image by using electrons instead of light to form an image.

Studying the Shape of Bones Using UV Light

Ultraviolet light was used to study the shape of the bones to understand what type of ichthyosaur it was, as the skeletons and the rock the specimens were kept in were almost the same color.

The researchers observed that the phosphate found in the tissues of ichthyosaurs likely contributed to preservation.

Although it is not yet possible to identify all types of fossilized tissue in the ichthyosaur, the new study confidently confirms the preservation of skin and possibly connective tissue, according to the researchers.

Decomposed fat covers the specimen

Most of the material surrounding and covering the specimen is likely decomposed fat, according to the study. Fat is a thick layer of fat, also called adipose tissue, located directly under the skin of all marine animals.

Delsett said scientists know from previous research that ichthyosaurs likely had blubber, like whales do today. She said their research confirms this, for a group of ichthyosaurs where it hasn’t been certain.

The researcher explained that blubber is another strong similarity between whales and ichthyosaurs, in addition to their body shape.

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