The Mystery of the Ichthyosaurus: Similar to the Dolphins but Related to the Turtles

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A new fossil reveals that these animals were probably warm-blooded, had insulating fat and used their coloration as camouflage for predators.

The ichthyosaurus has always been one of the great mysteries of animal life in the Jurassic. With aspect of dolphin or toothed whale, in reality they were marine reptiles that little had to do with the cetaceans. Or that was believed until now . An international team of researchers, including scientists from the State University of North Carolina and Lund University of Sweden, have discovered that their resemblance goes far beyond appearance . The molecular and microstructural analysis of a Jurassic Stenopterygius ichthyosaur (dated 180 million years ago)and found in Germany) reveals that these animals were probably warm-blooded, had insulating fat and used their coloration as camouflage for predators.

“Ichthyosaurs are interesting because they have many features in common with dolphins, but they are not related at all to these mammals that inhabit the sea,” explains the co-author of research published in the journal “Nature” , Mary Schweitzer , professor of science biological diseases in the State of North Carolina. But the enigma does not stop there: ” We are not too sure about its biology either . They have many characteristics in common with living marine reptiles, such as sea turtles; but we know from the fossil record that they gave birth to their young , which is associated with warm blood. This study reveals some of those biological mysteries ».

Johan Lindgren , associate professor at the University of Lund in Sweden and lead author, notes that the fossil was in very good condition, which has given the research team many clues: “Both the contour of the body and the remains of internal organs are clearly visible (…) Surprisingly, the fossil is so well preserved that it is possible to observe individual cell layersinside your skin»Says Lindgren.

The researchers identified cell-type microstructures that contained pigment organelles within the skin of the fossil, which could indicate that they used coloration as a camouflage against predators. In addition, they found traces of an internal organ, probably the liver. They also observed material chemically compatible with vertebrate fat , which is only found in animals capable of maintaining body temperature regardless of environmental conditions.

The samples were sent to several international laboratories, who, apart from performing several tests with mass spectrometry, extracted soft tissues from the samples and performed multiple high-resolution immunohistochemical analyzes. For its part, Lindgren’s team also found chemical evidence of subcutaneous fat. “This is the first direct chemical evidence of warm blood in an ichthyosaur , because fat is a characteristic of warm-blooded animals,” says Schweitzer.

The Mystery of the Ichthyosaurus: Similar to the Dolphins but Related to the Turtles

Whale skin and Camouflage

Overall, the findings indicate that the Stenopterygius had a skin similar to that of a whale and a coloration similar to that of many living marine animals, dark in the upper part and lighter in the lower part , which would provide the camouflage of the predators

“Both morphologically and chemically, we found that, although Stenopterygius would be considered a reptile, it lost the scaly skin, as did the leatherback turtle – the largest of the current sea turtles – which reduced resistance and increased its maneuverability. underwater, “says Schweitzer. Apart from these discoveries, the team highlights the importance of international collaboration to carry out complete multidisciplinary studies like this one.

 

Source: ABC Science

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