244 million Years Ago, Monsters Ruled The Seas

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A fossil skeleton found in central Nevada's desert years ago has been identified as belonging to a 30-foot-long sea monster that ruled beneath the waves 244 million years ago.

The ferociousness of the creature's teeth suggests that it was at the top of the food chain at the time — and that the time frame for its rise to the top was incredibly quick. The ichthyosaur has been dubbed Thalattoarchon saurophagis (from the Greek for "lizard-eating sovereign of the sea"), and it must have entered its reign just a few million years after one of Earths' biggest die-offs, known as the Permian-Triassic extinction event.

"It is a remarkable biotic recovery that appears to have proceeded faster in the marine than in the terrestrial biota," said Olivier Rieppel, a paleontologist at the Field Museum in Chicago who is a co-author of a paper on Thalattoarchon published online today by the Proceedings of the National Academy of Sciences.

The researchers said Thalattoarchon was apparently the first top predator to emerge in the marine environment after the Permian-Triassic extinction, which is thought to have killed off more than 90 percent of Earth's species. The cause of the extinction is the subject of a long-running debate, with catastrophic climate change among the prime suspects.

Previous studies have suggested that it took 10 million years for Earth's ecosystems to bounce back — but the latest research seems to provide evidence that the comeback was quicker under the sea.

"Ecosystems rebuild from the bottom up, and its appearance in the fossil record indicates the full recovery was reached only 8 million years after the P-T mass extinction," lead author Nadia Fröbisch, a paleontologist at the Leibniz Institute for Research on Evolution and Biodiversity's Museum für Naturkunde in Germany, said in an email. "The macropredator niche has been occupied ever since Thalattoarchon appeared — with different players, but the ecosystem structure was essentially modern."

The empire that this sea monster ruled was far different from present-day Nevada.

"At the time, all land masses were united in the supercontinent Pangea," Fröbisch explained. "Nevada was located in the Panthalassian Ocean, to the west of the supercontinent. The climate was very warm at the time, especially in the equatorial region, though this was slightly farther north. However, the climate would still be considered tropical. The Rockies started to rise in the late Cretaceous [66 million to 100 million years ago] and ended in the Eocene, about 35 million years ago."

The Thalattoarchon fossil was discovered in Nevada's Augusta Mountains in 1997 during a field expedition led by Rieppel and Martin Sander of the University of Bonn's Steinmann Institute — and since then, paleontologists have excavated a partial skeleton, including most of the skull, parts of the pelvic girdle and pieces from the hind fins.

he 5-inch-long (12-centimeter-long) teeth served as the tip-off for the creature's top-predator status. "The cutting edges were previously unknown for ichthyosaurs of that age," Fröbisch said. "The teeth are very large and sit in very robust and strong jaws, which overall indicate high biting force. This ichthyosaur was able to seize and cut prey similar in size to its own."

In a Field Museum news release, Rieppel said the discovery was "a good example of how we study the past in order to illuminate the future." So does this research suggest that a new top predator might emerge relatively quickly after the next mass extinction?

"Hmm — not really," Rieppel replied in an email. "History is inherently contingent — i.e., not predictive — and, as they say, it does not need to repeat itself."

But by studying how species recovered after past extinctions, "one hopes that certain patterns or generalities would become apparent that would reveal rules about the way a biota reconstitutes itself after a catastrophic impact," he said.

In today's news release, Fröbisch also emphasized the lessons that the distant past can teach us about the present and future.

"Every day, we learn more about the biodiversity of our planet, including living and fossil species and their ecosystems," she said. "The new find characterizes the establishment of a new and more advanced level of ecosystem structure. Findings like Thalattoarchon help us to understand the dynamics of our evolving planet, and ultimately the impact humans have on today's environment."

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