Largest marine reptile ever known to exist was discovered by an 11-year-old girl

Strolling a familiar beach and stumbling upon a relic from the age of dinosaurs sounds like pure fantasy, yet that is exactly what happened on England’s west coast.

A stretch of shoreline below Somerset’s crumbling cliffs yielded a bone so large that it challenged everything we thought we knew about prehistoric marine reptiles.

The fossil – a lower jaw more than 6½ feet long – promised a creature leagues beyond anything alive today. The find dated to around 202 million years ago, slotting it into the turbulent final chapter of the Triassic Period.

At that time, much of what is now Britain lay beneath a warm, shallow sea patrolled by meat‑eating giants. Their reign ended in a mass extinction, leaving only scattered bones to whisper their stories – until now.

Ruby and Ichthyotitan severnensis

Back in late May 2020, 11‑year‑old Ruby Reynolds and her father, Justin, headed for the mudflats of Blue Anchor, looking for fossils.

Justin spotted a four‑inch scrap of bone, “bigger than any piece of bone I’d ever found before,” he recalls.

Ruby wandered on and unearthed a second fragment twice that size. “It was just sort of lying there,” she says. “I was just happy, really.” Their excitement would soon ripple far beyond the shoreline.

Word reached paleontologist Dean Lomax, who holds posts at both the University of Bristol and the University of Manchester. He recognized echoes of another Somerset specimen lifted in 2016 by local collector Paul de la Salle.

That earlier jaw fragment, called a surangular, came together from several chunks that, Lomax remembers, “fit together perfectly like an ancient prehistoric jigsaw puzzle.”

Ruby’s discovery was eventually named Ichthyotitan severnensis, which literally translates to “giant fish lizard from the Severn.”

Ichthyotitan severnensis was a true monster

The first bone’s eroded edges left scientists yearning for more. “It suggests that it was from something unusual and exceedingly large,” Lomax says.

He and colleagues published a cautious description, but could not pin down the creature’s identity. “What we’d hoped for – we kept our fingers crossed – we hoped that maybe more specimens would come to light in the future,” he admits.

Ruby and Justin’s beachside haul delivered exactly that. After they emailed photographs – “Hey, Dr. Lomax – we think we’ve found another one of your giant ichthyosaur jawbones” – the research team raced to Somerset.

“Of course, they were quite right,” Lomax says. “They correctly identified these sections of bone as belonging to an ichthyosaur.”

Fresh collecting trips recovered still more pieces, leaving nearly two‑thirds of the jaw intact and in excellent shape.

Matching two huge jawbones

Comparison of the two Somerset jaws revealed striking similarities. Because both turned up in the same rock layer and displayed uncommon internal bone textures, the team concluded they belonged to one new species.

In a paper published in PLOS ONE, they proposed that the full animal stretched roughly 82 feet – “genuinely enormous, about the length of a blue whale,” Lomax says.

Scale alone does not grant a place in the record books; scientists also scrutinized microscopic structures inside the bone.

These matched the odd pattern seen in other super‑sized ichthyosaurs, nudging researchers to suggest these reptiles grew in a way unlike most of their scaly kin.

Whether Ichthyotitan severnensis belonged to the shastasaur group – the clade that once produced Triassic leviathans across the globe – remains uncertain until a complete skeleton surfaces.

Sizing up Ichthyotitan

The Somerset titan likely carried a lighter, more streamlined frame suited for open‑ocean cruising. Its jawbone alone outsizes a grown person by several feet.

If its proportions followed relatives such as Shonisaurus, the skull may have spanned over 10 feet, with paddle‑shaped flippers stretching wider than a living‑room couch.

Growth to such dimensions suggests a sea rich in food and free of bigger predators. Massive schools of squid‑like cephalopods thrived in Triassic waters, offering a banquet to long‑roaming hunters.

Stable‑isotope evidence from other ichthyosaur bones hints at warm‑blooded metabolisms, which, paired with live birth and sleek bodies, let them fill whale‑like niches long before mammals took the plunge.

Life in the Triassic was incredible

The Triassic often flies under the radar next to the Jurassic’s celebrity dinosaurs, yet biomechanist Kelsey Stilson calls it “a really weird time.”

Continents had only just fused into Pangaea, monsoon‑driven climates swung from drought to deluge, and both early dinosaurs and mammals were fresh on the scene.

“There were things that we can’t even possibly imagine in the past,” Stilson adds. “But we can get little hints, and this is one little hint at this larger picture of evolution on Earth.”

That broader picture shows ichthyosaurs rising fast after the end‑Permian mass extinction, then peaking in size just before the next cataclysm.

“No marine reptile ever reached such gigantic sizes ever again,” Lomax notes. Later Jurassic and Cretaceous ichthyosaurs shrank, perhaps pushed aside by changing oceans and by the emergence of other reptilian predators such as pliosaurs and mosasaurs.

Whales replaced Ichthyotitan severnensis

The last ichthyosaurs disappeared about 94 million years ago, vacating the top spot in marine food webs.

That gap lingered until hoofed mammals ventured back to sea some 50 million years ago, setting whales on their own path to titanic proportions.

The repeat story – big fish‑shaped predators evolving from land‑going ancestors – highlights how evolutionary solutions recur when similar ecological opportunities arise.

Modern blue whales now stretch beyond 100 feet and can weigh 180 tons, yet, length for length, they share the open ocean’s realm with Ichthyotitan in the fossil archives.

Their stories highlight the ocean’s capacity to nurture behemoths when food is ample and competition sparse.

What happens next?

Somerset’s cliffs erode a little more each winter. Storms tear at ancient mudstones, exposing new fossils overnight.

“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,” Lomax concluded.

“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.”

Beachcombers like Ruby and Justin now scan those shores with renewed purpose. Their lucky strike reminds us that scientific breakthroughs sometimes hide in plain sight, waiting for curious eyes and a little persistence.

The sea claimed Ichthyotitan severnensis long before humans walked Europe, yet its story shows that even after millions of years, a coast‑side ramble can rewrite natural history.

The full study was published in the journal PLOS ONE.

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