Prehistoric ocean giant discoveredin the U.S.

01 January, 2022

The fossil of a giant sea reptile with a skull the size of a grand piano has been discovered in Nevada in the western United States. The most remarkable thing about the find is its age, 246 million years. Very large animals did not exist before that time, which means that the beast, as far as is known, was the first giant animal on Earth.

fossil skull
The fossil skull of Cymbospondylus youngorum, an extinct ichthyosaur from the Triassic period. The skull is the size of a large grand piano. Photo: Martin Sander, Natural History Museum of Los Angeles County

The new species, which has been named Cymbospondylus youngorum, belonged to the ichthyosaurs, the fish lizards, a group of reptiles that dominated the world’s oceans during the time of the dinosaurs. Their origins are shrouded in obscurity, but they definitely had no closer kinship with the dinosaurs (who never developed any marine, or even freshwater, species).

The Ichthyosaurs appeared without warning about 249 million years ago, at the very beginning of the Triassic period, shortly after the greatest catastrophe suffered by life on Earth; The mass extinction at the end of the Permian period 252 million years ago. About 90 percent of Earth’s species were wiped out, and ecosystems on the planet were completely restructured.

skull reptile
The skull of the newly discovered sea reptile. The tooth armament shows that it was a highly active predator that likely dominated the ecosystem of the oceans 246 million years ago. Photo: Natalja Kent, Natural History Museum of Los Angeles County.

Record-breaking growth

Perhaps the ancestors of the ichthyosaurs benefited from the disaster. Anyway, judging by the fossil testimonies, they very quickly became the most important predators of the oceans – and the newly discovered species reveals that in record time, in the space of just three million years, they reached enormous body size. Cymbospondylus youngorum grew 15-17 meters in length. The huge head was about two feet long, the size of a large piano, with jaws provided with rows of large, pointed teeth.

This is strange. On dry land, it was a very long time, another 40 million years, before the first giant dinosaurs appeared on the scene. And much later in Earth’s history, when mammals took over the main roles, it took 45 million years before the whales developed giant shapes. So why did things move so fast for the ichthyosaurs? And what was the reason for the sudden growth?

reconstruction of the newly discovered sea reptile
Reconstruction of the newly discovered sea reptile. Its length was 15-17 meters, and the skull reached a length of two meters. The picture shows its likely prey, ammonites, shelled cephalopods, as well as conodonts, a type of jawless fish. Graphics: Stephanie Abramowicz, Natural History Museum of Los Angeles County

Many prey animals

The answer may be the emergence of a rich fauna of potential prey, primarily so-called ammonites, an extinct group of shelled cephalopods, and conodonts, a similarly extinct group of jawless fish. The jaws and teeth of ichthyosaur were perfectly adapted to feed on that kind of prey.

Another reason may be that the ichthyosaurs lacked competition for a long time. The researchers, whose findings are published in the journal Science, have made calculations showing that the food chain in the oceans at the beginning of the Triassic could well house monster-sized predators.

The remains of Cymbospondylus were excavated from sedimentary layers in the Augusta Mountains of central Nevada. They have now been exhibited at the Natural History Museum in Los Angeles, California.

Reptiles have lived in the seas for a very long time, and even today there are a number of marine species. The sea iguana is the only marine lizard, but the sea turtles include seven species, and the sea snakes just over 60 species. Two species of crocodiles, the delta crocodile and the lace crocodile, live partly in marine environments.

In the Middle Ages of the Earth, from Triassic to Cretaceous, the diversity was even greater, and some species became enormously large, as large as the great whales of our time . The most famous are the fish lizards (ichthyosaurs), the swan lizards (plesiosaurs), as well as the mosasaurs. All of them were predators that dominated their respective ecosystems. The fish lizards, which had the same body shape as today’s dolphins, died out 90 million years ago, while the swan lizards and mosasaurs were wiped out along with the dinosaurs when Earth collided with an asteroid 66 million years ago.

Source: Science

Text: Roland Johansson/Beatrice Nordensson/TT
Photo: Martin Sander, Natalja Kent, Natural History Museum of Los Angeles County/TT
Graphic reconstruction: Stephanie Abramowicz, Natural History Museum of Los Angeles County/TT

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