Fossil collector Paul de la Salle came across a large chunk of bone on the beach near Lilstock, Somerset, in May 2016. He later returned and discovered more pieces that altogether formed a bone measuring 1 meter long, or about 3.28 feet.
“Initially, the bone just looked like a piece of rock," de la Salle said in a statement this week. "But after recognizing a groove and bone structure, I thought it might be part of a jaw from an ichthyosaur."
De la Salle contacted several experts, who ultimately identified the specimen as an incomplete bone from the lower jaw of a giant ichthyosaur, an aquatic predator that lived some 205 million years ago and measured up to 20 meters long, or about 82 feet. The shark-like reptiles vanished 95 million years ago, about 30 million years before the last non-avian dinosaurs went extinct.
Two of the experts de la Salle contacted were Dean Lomax, an ichthyosaur expert at the University of Manchester, and Judy Massare, professor emerita of geology at SUNY College at Brockport, New York. Lomax and Massare traveled to the Royal Tyrrell Museum of Palaeontology in Alberta, Canada, to compare the newfound specimen to the fossil of the largest ichthyosaur known, the 69-foot Shonisaurus sikanniensis. They determined the new fossil is substantially bigger than the same bone in the jaw of Shonisaurus.
"As the specimen is represented only by a large piece of jaw, it is difficult to provide a size estimate, but by using a simple scaling factor and comparing the same bone in S. sikanniensis, the Lilstock specimen is about 25 percent larger. Other comparisons suggest the Lilstock ichthyosaur was at least 20 to 25 meters," Lomax said in a statement released by the University of Manchester on Monday.
De la Salle, Lomax, Massare and geologist Ramues Gallois co-authored a study describing the discovery, which was published Monday in the scientific journal PLOS ONE.
The authors concluded that size estimates suggest the new bone belonged to one of the largest animals that ever lived.