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


Ichthyosaurs, meaning "fish lizard" in ancient Greek, are large extinct marine reptiles. They are the distant relatives of lizards and snakes, and were the most specialised 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 preserve outer body shape in the last, large 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 approximately 150 million years old.


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


Several fossils from the Late Jurassic are found in the Solnhofen area in southern Germany. These include the Archaeopteryx, which is usually recognised as the first bird, and various other animals. Many of these animals are preserved in soft tissues 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, approximately 150 million years old, have been described in the study.


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


Characteristics Of The Ichthyosaurs


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


The other specimen is a complete tail fin, and is preserved with the tail vertebrae and the soft tissues around. This confirms that ichthyosaurs also in this group had a moon-shaped tail, like their ancestors, the study said.


The researchers analysed the soft tissue samples in order to see what it contained.


Findings Of The Study


In a statement issued by PeerJ, Lene Liebe Delsett, the lead author of the study, said the complete specimen is really what makes this project unique because it tells a complete story. She explained 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. 


She said the researchers do not know why this ichthyosaur entered the lagoons, but it might be the reason why it died. 


She added that seeing the specimen makes an impact because it is so obviously a complete, dead animal body, where one can see its shape because of the unique preservation.


According to the study, the ichthyosaur, during or after its death, landed on its back and side on the seafloor, and was covered in fine sediments. It was preserved due to a little oxygen, until it was found and excavated in 2009.


Understanding The Soft Tissue Using X-Ray Crystallography


The researchers have done a first description of the specimen in the paper. In order to understand the soft tissue, the scientists took small samples from the soft tissue in the tail and looked at it through X-ray crystallography and a scanning electron microscope. X-ray crystallography is a tool used for determining the atomic and molecular structure of a crystal. The crystalline atoms cause a beam of X-rays to diffract into many specific directions. 


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


Studying The Shape Of Bones Using UV Light


Ultraviolet light was used for studying the shape of the bones to understand which type of ichthyosaur these are, because the skeletons and the rock the specimens were preserved in, had almost the same colour.


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


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


Decomposed Blubber Covers The Specimen


The major part of matter that surrounds and covers the specimen is probably decomposed blubber, the study said. Blubber is a thick layer of fat, also called adipose tissue, directly under the skin of all marine animals. 


Delsett said that scientists know from earlier research that ichthyosaurs likely had a blubber, like whales have today. She said that their research confirms this, for s group of ichthyosaurs where this has not been certain. 


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