Dolphins had a twin reptile was Jurassic with whale fat and warm blood



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Ichthyosaurs and dolphins are the archetypal examples of convergent evolution in action, in which two completely unrelated species take on almost identical characteristics. The discovery of a new fossil of ichthyosaurus suggests that this creature of the Jurassic era was even more like a dolphin than we enjoyed, with warm blood, grease and even similar camouflage.

A remarkable 180-million-year-old fossil found in the Schist Formation of Posidonia, southwest of Germany, Stenopterygius Ichthyosaurus, is providing the best evidence yet that ichthyosaurs – ancient marine reptiles, similar to dolphins – were warm-blooded creatures.

The preservation of the new fossil is so good, said lead researcher Johan Lindgren of the University of Lund in Sweden, who was able to see the contours of the animal's original, supple skin along with evidence of fat underneath. In addition, he and his colleagues were able to detect internal organs and, on a molecular scale, traces of cellular layers within the fossilized skin. It is now the first example of fossilized ichthyosaur grease in the scientific literature, pointing to ichthyosaurs as warm-blooded or endothermic organisms.

Ichthyosaurs were contemporaries of dinosaurs, but were strikingly similar in appearance to modern toothed whales, especially dolphins. Scientists suspect that ichthyosaurs may be warm-blooded based on estimates of their swimming speed, but this new finding, the details of which were published today in Nature, is the first to provide evidence in the form of fossilized subcutaneous soft tissue.

In modern aquatic mammals, fat, besides acting as an insulation layer against the cold, helps in buoyancy and serves as a deposit of fat. Cold-blooded creatures, who tend to live in hot climates, do not really need it.

"Their main function is isolation," explained Lindgren GizmodoThus, there is no need for a cold-blooded animal to have fat. That said, adult individuals of the modern leatherback turtle are fat, but have high metabolic rates compared to "typical" reptiles, and whale fat is one of many adaptations in this species to allow ventures in cold and cold water. [areas].

But unlike sea turtles laying eggs on the beach, ichthyosaurs have given birth to a young, warm-blooded life, according to Lindgren.

To study the fossil, Lindgren and her colleagues applied an experimental multidisciplinary approach to analyze both the structure and chemistry of preserved soft tissues. The researchers were able to identify microstructures similar to the cells, which contained pigments inside the animal's skin and traces of internal organs, including the liver.

"We also showed that the inside of his skin was lined with fat, to suggest that ichthyosaurs were warm-blooded," Lindgren said. "The fossil is so well preserved that we are able to distinguish cells, cellular organelles and traces of the original biochemistry."

To which he added: "Our analyzes have revealed that this ichthyosaur has been circumvented; that is, it had a dark upper surface and a clear belly. "

Countershading is also present in dolphins, serving as camouflage. In the case of ichthyosaurs, camouflage against repression may have protected them from predators, such as the aerial pterosaurs from above, or the aquatic pliosaurs from below, the researchers speculate.

Lindgren said his team "conducted the most comprehensive and thorough research ever conducted on a soft tissue fossil," but admitted that it relied on the analysis of a single individual. Future research "needs to be expanded to also include other specimens," he said.

The good news is that this may be possible. Fossils of ichthyosaurs are exceptionally common, so paleontologists can discover more fossils as primitive as this.

[Nature]

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