Earth’s “first giant” was an oceanic reptile with a two-meter skull

Whales are now the largest creatures on Earth, but this was not always the case. In the last 300 million years, during the evolutionary race of the oceans, dozens of lineages of reptiles and mammals have occupied the marine ecosystem, and some of them were exceptionally large.

250 million years ago, the first vertebrates to invade the oceans after the Permian-Triassic mass extinction were ichthyosaurs, that lasted for most of the following period, the Mesozoic, which ended 66 million years ago.

Rapid explosion of the evolution of your body size

Now the analysis of some new ichthyosaur fossils, dating back to the early stages of the Age of Dinosaurs, discovered in the mountains of northwestern Nevada (United States), has shown that in this prehistoric period some inhabitants of the oceans experienced an early and rapid explosion in the evolution of their body size. The new species of aquatic reptile could represent the first giant animal to ever live on Earth.

Led by Martin Sander of the Los Angeles Museum of Natural History, the study describes the well-preserved remains of a new (and huge) species of ichthyosaur, the Cymbospondylus youngorum, 244 million years ago.

His skull alone is almost six feet long, like a grand piano, which means that the entire specimen could measure about 18 meters, more or less like a current adult minke whale, which is uOne of the largest whales out there.

Relative with the size similar to a laptop

But the most important thing about this find is not the size, but the age of the species. According to Sander and his team, C. youngorum evolved just 2.5 million years after the Cartorhynchus, the oldest relative of the ichthyosaur, whose oldest fossil, found in China, is 8 million years old and about the size of a laptop.

This difference in size shows how quickly the body size of the ichthyosaurs evolved from the appearance of the group to the C. youngorum.

“The speed of the gigantism of ichthyosaurs may be unmatched among marine vertebrates,” the authors conclude.

In fact, The study makes a comparison with the current whales and reveals that, while they used about 90% of their 55 million years of history to become the oceanic giants that are, ichthyosaurs took less than 1% of their 150 million years of evolutionary history to achieve this.

Finally, the authors suggest that despite the absence of many primary producers after the Permian extinction 252 million years ago, the Triassic marine food webs were capable of supporting such enormous creatures.

In an analysis linked to the results of this study, paleontologists Lene Delsett of the University of Oslo and Nicholas Pyenson of the University of Washington warn that the history of the ichthyosaurs “shows us that ocean giants are not a guarantee of marine ecosystems, which is a valuable lesson for all of us in the Anthropocene.”

“Especially if we want to maintain the presence of the surviving ocean giants among us that contribute to our own well-being,” conclude both paleobiologists. (I)