Earth’s First Giant – Eurasia Review

A two-meter-long skull, a total body length of 17 meters, a weight of 45 tons, fins that paint the sea – what looks like a sperm whale is actually a reptile and lived in the oceans about 250 million years ago. Today, an international team of researchers led by the Universities of Bonn and Mainz, as well as Claremont Colleges and the Los Angeles County Museum of Natural History, report on this first giant animal that ever evolved. Researchers describe a new species of ichthyosaur, also known as a “saurian-fish” – the towering skeleton, larger than that of Tyrannosaurus Rex was excavated in the US state of Nevada.

The study now proves that ichthyosaurs evolved to their impressive size in just three million years, much faster than the evolution of gigantism in whales today. With the help of modeling, the team discovered that ichthyosaurs lived in environments that were excellent for supporting bodies of such large size. The results thus show how marine ecosystems can form and react to abiotic changes such as climate, atmosphere or water conditions. The study was published in the journal Science.

While dinosaurs ruled the earth, ichthyosaurs and other aquatic reptiles ruled the waves. The evolving fins and hydrodynamic shapes of the body seen in both fish and whales, ichthyosaurs swam the ancient oceans for most of the dinosaur era. Ichthyosaurs derive from a still unknown group of terrestrial reptiles and breathe air themselves. science long before dinosaurs, and they have captured the popular imagination ever since, ”says lead author Dr Martin Sander, professor of vertebrate paleontology at the University of Bonn and research associate at the Dinosaur Institute of Natural History Museum in Los Angeles. County (NHM).

He and his colleagues have worked steadily for 30 years on a rock unit called the Fossil Hill Member in the remote Augusta Mountains of Nevada, USA, as the mountains connect our present to the ancient oceans, opening a window to the Triassic of 247. , 2 to 237 million years ago. It was also in the Fossil Hill Member, in 1998, that the first remains of the new giant animal now described were unearthed, initially in the form of part of the vertebrae.

“The significance of the find was not immediately apparent,” Sander notes, “as only a few vertebrae were exposed on the side of the canyon. However, the anatomy of the vertebrae suggested that the animal’s front end could still be hidden in the rocks. One day in September 2011, the crew tested this suggestion by excavation, finding the skull, forelimbs and chest area well preserved. The giant that appeared was given the name Cymbospondylus youngorum, the second part of the name referring to a local brewery.

Anatomical description of the animal

So how do you deal with this awesome discovery from a long time ago? The first task was to describe the anatomy of the skeleton using traditional paleontological methods and to determine when the animal had lived. To find out how the saurian fish evolved to such a size, the researchers compiled a lot of data from the literature and used it as the basis for computational and modeling analyzes. The result was that the new ichthyosaur lived in the Middle Triassic (247-237 million years ago) and was over 17 meters long, as big as a sperm whale. The find represents the largest animal ever discovered from that time, whether on land or in the sea.

“As far as we know, it was even the first giant creature to ever inhabit Earth,” Sander says. More detailed analyzes revealed that Cymbospondylus youngorum lived 246 million years ago – about three million years after the first ichthyosaurs changed from terrestrial reptiles to aquatic reptiles. Even though three million years seems long by our standards, “It’s an unbelievably short time to grow that big,” Sander points out.

Computer models for ecosystem reconstruction

So the new findings also raised a new question: How could a species among ichthyosaurs evolve so quickly into such a giant? To find out, the team used modeling to recreate the ecosystem’s energy flow at the time. “A fairly unique aspect of this project is the integrative nature of our approach,” says lead author Dr. Lars Schmitz, associate professor of biology at Scripps College and research associate at the Dinosaur Institute.

“After having described in detail the anatomy of the giant skull and thus understood how this animal relates to other ichthyosaurs, we wanted to understand the significance of the new discovery in the context of the large-scale evolutionary model of body size. ichthyosaurs and whales. To do this, we needed to understand how the fossil ecosystem preserved in the Fossil Hill member might have functioned. “

Using sophisticated computer models, the authors examined the likely energy that flowed through the food web of the fossil hill fauna, recreating the ancient environment using data, concluding that marine food webs must have been able to endure an even more colossal meat-eating ichthyosaur.

“Understanding the functioning of this food web from ecological modeling was very exciting,” says Dr Eva Maria Griebeler, professor of evolutionary ecology at the University of Mainz. She and her team led the ecological modeling. His conclusion: “Due to their large size and the resulting energy requirements, the densities of the larger ichthyosaurs of the fossil hill fauna, including Cymbospondylus youngorum must have been significantly lower than what our field census suggested.

Modern whales evolved much more slowly

The researchers found that while cetaceans and ichthyosaurs evolved very large, their respective evolutionary trajectories to gigantism were different. According to Schmitz, “Evolutionary models show very clearly that ichthyosaurs experienced an initial boom in size, becoming giants early in their evolutionary history, while whales took much longer to reach the outer limits of the enormous . ”

This is because ichthyosaurs seem to have benefited from an abundance of eel-like conodonts as well as a variety of ammonites, the shell relatives of modern cuttlefish and octopus, especially the nautilus. The now extinct ammonites filled the ecological void after the mass extinction of the late Permian and found excellent living conditions. “We speculate that ichthyosaurs may also have evolved so rapidly because they were the first larger creatures to inhabit the world’s oceans and were exposed to less competition,” says Martin Sander.

On the other hand, certain types of plankton were an important driving force for the evolution of the size of whales. In addition, the different species of whales and dolphins have evolved differently, associated with certain food specializations. Baleen whales, for example, have lost their teeth, while giant squid-hunting sperm whales have retained them. One thing is for sure: Although their evolutionary pathways have been different, whales and ichthyosaurs have relied on exploiting niches in the food chain to make it really big.

“This discovery and the results of our study highlight how different groups of marine tetrapods developed body sizes of epic proportions under somewhat similar circumstances, but at surprisingly different rates,” said NHM’s associate curator of mammology. (Marine mammals), Dr Jorge Velez. Juarbé. “Another interesting aspect is that Cymbospondylus youngorum and the rest of the fossil hill fauna bear witness to the resilience of life in the oceans after the worst mass extinction in Earth history. You can tell this is the first big splash for tetrapods in the oceans. “

For a beer – How the Cymbospondylus youngorum to his name

The new name of the species, Cymbospondylus youngorum, honors a happy coincidence, the sponsorship of fieldwork by the Great Basin Brewery of Reno, owned and operated by Tom and Bonda Young, the inventors of the famous Icky beer which features an ichthyosaur on its label.

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