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Replica of two Shonisaurus, a species of ichthyosaurs
Photo: picture alliance / Nobumichi Tamura
Ottersaurs have fascinated science for years: The ocean liners were probably the largest vertebrates of their time and evolved in record time.
In the US state of Nevada, a German-American research team has now discovered another fossil of a huge ichthyosaur that roamed the ocean 246 million years ago.
The skull of the previously unknown species Cymbospondylus youngorum alone was about two meters long and as big as a concert grand. Overall, the animal was probably around 18 meters long and 45 tons in weight, estimates the group around the German scientist Martin Sander in the journal "Science". This is roughly the size and scope of today's fin whales.
Through the find they were able to gain further knowledge about the dinosaur species.
It is not only the size of the ancient animals that is striking, but also that such ocean liners evidently evolved in record time.
Because only relatively "shortly" before, around 252 million years ago, the mass extinction at the end of the Permian Period had wiped out around 80 percent of marine life.
The ichthyosaurs quickly developed into different species and occupied the niches in the sea that had become vacant after the mass extinction.
"The early evolution of the ichthyosaurs apparently showed a rapid rise in gigantism, and Cymbospondylus youngorum is the largest vertebrate of its time, both on land and in the water," write Lene Liebe Delsett and Nicholas Pyenson of the Smithsonian Institution in Washington in a " Science "comment.
The evolutionary speed of growth may be unprecedented among ocean vertebrates.
While whales took about 90 percent of their 55 million year history to develop into giants, ichthyosaurs would have done so early in their 150 million year evolution.
Big eyes and a penchant for squids
The first - currently known - ichthyosaur-like animal appeared about 249 million years ago and was not even half a meter tall. According to the scientists, it is surprising that another 2.5 million years later such a giant as the recently found Cymbospondylus youngorum was living in the seas - because its large body mass had to be supplied with energy, so the oceans had to have enough prey ready. From the anatomy of the mouth and teeth, the researchers conclude that the species ate fish and octopus as well as smaller marine reptiles. The ichthyosaur had very large eyes, which gave it further advantages in foraging.
Even somewhat larger ichthyosaurs - such as the more than 20 meter long Shonisaurus popularis and Shastasaurus sikanniensis - did not appear until 20 to 30 million years later, according to current knowledge, and the first rural dwellers of comparable weight only more than 40 million years later, as the team emphasizes .
Amazing similarities with whales
The ichthyosaurs only disappeared almost a hundred million years ago, possibly due to climatic changes, Delsett and Pyenson continue to write.
“The history of the ichthyosaurs shows us that sea giants don't necessarily have to be part of marine ecosystems.
This is a valuable lesson for all of us in the Anthropocene, especially if we want to maintain the presence of the surviving ocean liners today. "
Three years ago researchers discovered a fossil on a beach in Great Britain that could belong to one of the larger ichthyosaurs.
They estimated that the dinosaur that went with it was at least 20 to 25 meters long, possibly larger.
Ichthyosaurs inhabited the earth for a total of around 150 million years.
For comparison: whales (Cetacea) have only existed for a good 50 million years.
That being said, ichthyosaurs and whales share a number of things in common.
These include extreme body size, locomotion, especially with the help of the caudal fin, and the fact that forerunners of both groups had already lived on land.
sug / dpa