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Read the given passage and answer the question that follows: The Mesozoic era wasn't just the age of dinosaurs. Reptiles of all sorts thrived through the Triassic, Jurassic and Cretaceous eras at the same time our favourite dinosaurs were roaming on land. Long-necked plesiosaurs, shark-shaped ichthyosaurs, toothy mosasaurs and many more saurians were swimming through the ancient seas, their success underwritten by a suite of anatomical specialisations. From the time the four-paddled, long-necked Plesiosaurus was named in 1821, palaeontologists generally thought of marine reptiles as comparable to lizards, snakes and crocodiles in the terrestrial realm. Marine reptiles were thought to be cold-blooded, their body temperature determined by the surrounding seawater. And scientists didn't know whether the ancient creatures had blubber, scales, smooth skin or some other sort of body covering. During the past three decades, however, a new wave of palaeontological interest has fundamentally changed how experts think about the likes of Mosasaurus and Ichthyosaurus. The repeated evolution of reptiles that lived entirely at sea was possible thanks to an array of adaptations that are still being uncovered by researchers. One of the features that allowed Mesozoic marine reptiles to thrive beneath the surface is that they had blubbery bodies. Many millions of years before whales and seals would evolve blubber, marine reptiles were already enjoying the benefits of the thick subcutaneous fat. In 2018, palaeontologists described a fossil of the Early Jurassic ichthyosaur Stenopterygius that preserved parts of the marine reptile's skin as well as remnants of fats and proteins that made up the animal's flesh. Which of the following statements accurately describes the central theme of the passage?