Earliest ichthyosaur

About 250 million years ago, ocean water covered what is now called Flowerdalen (“Valley of Flowers”) in modern Norway. Life in these waters was different from what it was just 252 million years ago, when the end-Permian mass extinction eliminated 90 percent of marine species from the planet. What remained were bold opportunists, including a species of sea-dwelling lizard called an ichthyosaur that evolved fins from land-dwelling legs.

When they died, their remains attracted sediments that over millions of years formed limestone time capsules that now rest among eroded mudstones in the Valley of the Flower. These Norwegian “concretions” preserved the bones of early marine fauna, including the adaptable ichthyosaur, for millennia to come.

Now, huh new ichthyosaur discovery from the valley has wide significance for the history of that time and the dinosaurs.

Read more: The Permian Extinction: Life on Earth Almost Extinct During the ‘Great Dying’

An unexpected find

In 2014, scientists moved a large number of concretions to the Natural History Museum at the University of Oslo, including some that were thought to be too old to contain ichthyosaur remains. But subsequent research found that they did, and dated the bones to 250 million years ago, long before (1.2 million years) before researchers thought the reptiles migrated into the sea. What’s more, the older specimen appeared well-evolved, with a light, spongy bone structure suitable for life underwater.

From the analysis of the vertebrae and other parts, the Swedish and Norwegian researchers concluded that the lizard roamed pelagically, away from the sea floor and shore, and also had a strong metabolism. Such features are common in aquatic tetrapods (they have four legs), but are remarkable in such an old lizard. How did the ichthyosaur get them so quickly?

The study suggests that the new species predated the mass extinction at the end of the Permian and thus the Mesozoic era, challenging the idea that the “main lineages of reptiles” first appeared during the latter, the age of the dinosaurs.

In other words, the first large reptile may have been an ichthyosaur, a creature that looked like a full-bodied dolphin and was only about three meters long (according to one estimate). Early ichthyosaurs sometimes reached only a meter in length, but later grew to resemble a giant fish millions of years later.

Origin story

If ichthyosaurs preceded the end-Permian mass extinction, when and where did they originate? The study lacks details and acknowledges the need for more discoveries to be made “in even older Svalbard rocks [in Norway] and elsewhere in the world.”

The study certainly disagrees with what it calls textbook narratives of lizards wandering downshore after extinction “to take advantage of the marine predator niches left vacant” by the mass extinction. According to the researchers, the lizards should not have come down; they were already there.

Scientists have discovered ichthyosaur fossils around the world, in Thailand, Japan, Canada and China, where continental drift left them to be found. Until recently, the oldest record came from Nevada, which dates back to about 249 million years ago and showed the same spongy bone structure key adaptation. Like a study found that these lizards evolved rapidly during the first few million years of aquatic life and then more slowly.

Source link

Leave a Reply

Your email address will not be published. Required fields are marked *