Largest known marine reptile discovered is a giant ichthyosaur

The discovery of a second massive jawbone, over two meters in length, on a beach in Somerset, UK, has recently piqued the interest of paleontologists. This fossil, along with the first one found, has been identified as belonging to a previously unknown species of giant ichthyosaur named Ichthyotitan severnensis – a marine reptile from prehistoric times.

Researchers estimate that this creature would have spanned more than 25 meters in length, akin to the size of a blue whale.

Discovery of the marine reptile Ichthyotitan severnensis

This significant find was made by Justin and Ruby Reynolds, a father and daughter duo from Braunton, Devon. During a fossil hunting trip in May 2020 at Blue Anchor, Somerset, 11-year-old Ruby stumbled upon the first fragment of this colossal jawbone. 

Realizing the importance of their find, they contacted Dr. Dean Lomax, a leading ichthyosaur expert and a paleontologist at the University of Manchester as well as a research fellow at the University of Bristol. Lomax.

They then reached out to Paul de la Salle, a seasoned fossil collector who had discovered the first giant jawbone in 2016 along the same coastline.

A multimillion-year-old jigsaw puzzle

“I was amazed by the find,” Lomax said. “In 2018, my team (including Paul de la Salle) studied and described Paul’s giant jawbone and we had hoped that one day another would come to light. This new specimen is more complete, better preserved, and shows that we now have two of these giant bones – called a surangular – that have a unique shape and structure. I became very excited, to say the least.”

Fueled by this initial success, Justin, Ruby, Paul, Lomax, and several family members returned to the site to search for more pieces. Their efforts were fruitful, eventually piecing together more fragments that fit perfectly together, like a multimillion-year-old jigsaw puzzle.

New species of giant marine reptile 

The analysis revealed that these jawbones belonged to a new species of giant ichthyosaur, which they named Ichthyotitan severnensis or “giant fish lizard of the Severn.”

These fossils, dating back approximately 202 million years to the end of the Triassic Period, represent some of the last members of the Shastasauridae family before they disappeared due to a global mass extinction event.

This discovery also aligns with findings of other large ichthyosaurs, such as Shonisaurus sikanniensis from Canada and Himalayasaurus tibetensis from China, although the new species appears around 13 million years after these relatives.

Dr. Lomax invited Ruby and Justin to join his research team in studying and naming this prehistoric creature. Ruby, now recognized as a young scientist, said that “it was so cool to discover part of this gigantic ichthyosaur. I am very proud to have played a part in a scientific discovery like this.”

Biological limits of vertebrates 

Further investigations into the bones by Marcello Perillo, a master’s student from the University of Bonn, confirmed the ichthyosaur origin and revealed that the creature was still growing at the time of its death. 

“We could confirm the unique set of histological characters typical of giant ichthyosaur lower jaws: the anomalous periosteal growth of these bones hints at yet to be understood bone developmental strategies, now lost in the deep time, that likely allowed late Triassic ichthyosaurs to reach the known biological limits of vertebrates in terms of size,” Perillo explained.

“To think that my discovery in 2016 would spark so much interest in these enormous creatures fills me with joy. When I found the first jawbone, I knew it was something special. To have a second that confirms our findings is incredible. I am overjoyed,” de la Salle said.

“This research has been ongoing for almost eight years. It is quite remarkable to think that gigantic, blue whale-sized ichthyosaurs were swimming in the oceans around what was the UK during the Triassic Period. These jawbones provide tantalizing evidence that perhaps one day a complete skull or skeleton of one of these giants might be found. You never know,” Lomax concluded.

The study is published in the journal PLoS ONE and the jawbone will soon go on display at the Bristol Museum and Art Gallery.

Image Credit: Sergey Krasovskiy.

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