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Fossil ichthyosaur bacon is proof that they were warm-blooded



  Ichthyosaurs

An approximately 180-million-year-old ichthyosaur fossil contains preserved skin with pigmentation and hustle and bustle. (Credit: Johan Lindgren)

For the first time, researchers have identified blubber and other soft tissue conserved in an early Jurassic ichthyosaur. The new interpretation of the 1

80-million-year-old fossil suggests that the extinct marine reptiles were warm-blooded.

Ichthyosaurs floated the seas of the Mesozoic and were in a timely manner with dinosaurs. They are often compared to modern toothed whales, especially porpoises (although at least one ichthyosaur species has attained a blue-whale size). Many paleontologists have theorized that animals, like modern whales, are warm-blooded, although evidence supporting the idea has been largely unclear. However, researchers today describe the results of a new and refined analysis of a specimen of the ichthyosaur species Stenopterygius, conserved with a portion of the skin, including pigmentation, fat, and possibly liver tissue (and bonus, gastric contents).

The researchers used ultraviolet light, special X-rays, and other techniques to determine the composition of the fossil. They identified remnants of smooth skin that had no scales and resembled those of a porpoise. The upper and lower layers of the skin were preserved together with an underlying fat or fat layer.

Identification of the blub confirmed by additional molecular analysis provides the strongest evidence that ichthyosaurs were warm-blooded. Blubber isolated, stores energy as fat and provides buoyancy. Today, the only animals with the layer of protective fat are warm-blooded amniots (mammals, reptiles and birds) who spend their entire lives or most of their lives in cold water (such as whales, seals, polar bears, sea turtles and penguins).

Finding excitement on an ichthyosaur is one example of convergent evolution when unrelated animals occupying similar ecological niches develop the same trait.

The resulting pigmentation on the skin indicates that Stenopterygius had a clearing belly, darker back), a common stealth strategy for modern predators. In addition to the difficulty of visualizing the animal, counter-shading can help with thermoregulation.

The research appears today in Nature .

  Ichthyosaur Illustration (Credit: Johan Lindgren)

An illustration of the ichthyosaur fossil with stomach contents (dotted outline), possible liver tissue (dashed outline), and skin and fat (mid-gray area). (Picture credits: Johan Lindgren)


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