What was the largest aquatic dinosaur

Largest marine dinosaur discovered

Almost as big as a blue whale: a marine dinosaur discovered in Great Britain could have been one of the largest animals in the entire history of the earth. Because the ichthyosaur was up to 26 meters long, as estimates based on its jawbone suggest. The huge reptile proves that primeval gigantism was not limited to land-based dinosaurs. Further finds of very similar jawbones could come from even larger marine dinosaurs, the researchers report.

The Cretaceous Oceans were the realm of the ichthyosaurs. The agile, warm-blooded marine dinosaurs hunted fish and other vertebrates, but did not shy away from attacks on their fellow animals. Fossil finds of pregnant ichthyosaur females also show that these marine dinosaurs were already viviparous.

Bones found on the beach

A find from the south of England now proves how big the marine dinosaur could get. On the beach at Lilstock in Somerset, the fossil collector Paul de la Salle came across an unusual bone in May 2016: “At first the bone looked more like a stone, but after seeing the structure of the bone, I suspected it could be the jawbone of a marine dinosaur “, Reports de la Salle.

The bone, which was broken into several fragments, was a good three feet long. More detailed studies by ichthyosaur expert Dean Lomax from the University of Manchester have now confirmed that it is the 205 million year old part of the lower jaw of an ichthyosaur - the so-called suprangular bone.

The fossil jawbone of the Lilstock ichthyosaur © Dean Lomax / University of Manchester

As the researchers report, the morphology of the jawbone is similar to that of Shonisaurus sikanniensis, which was discovered in Canada, so it could have belonged to the same genus. With a length of 21 meters, the Canadian specimen was the largest ichthyosaur known to date.

Up to 26 meters long

But the newly discovered ichthyosaur could have been even bigger. “It is difficult to estimate the size of a jawbone alone, but we can compare this bone with that of the very similar Shonisaurus sikanniensis,” explains Lomax. The comparison showed that the ichthyosaur from Lilstock must have been even 25 percent larger than its Canadian relative.

"The comparisons suggest that the English Shonisaurus was at least 20 to 25 meters long," says Lomax. The marine reptile may even be 26 meters long - almost the size of a blue whale. The ichthyosaur was one of the largest animals in the history of the earth.

An even bigger copy?

Also exciting: as early as 1850, a similar, around 208 million year old bone was discovered in Aust in Gloucestershire, England. Because these bones were also incomplete in the rest of the fossil, there was disagreement as to whether it was the relic of a dinosaur or a marine reptile.

The discovery of the Lilstock ichthyosaur and its jawbone now provides new evidence for this case: “One of the Aust bones could also be an ichthyosaur suprangular,” says Lomax. "If this should be confirmed, then this animal could have been even bigger than the Lilstock dinosaur." (PLoS ONE, 2018; doi: 10.1371 / journal.pone.0194742)

(University of Manchester, April 10, 2018 - NPO)

April 10, 2018