For decades, Liopleurodon ferox has intrigued paleontologists. This short-necked marine reptile inhabited the waters of present-day Britain and France approximately 163 million years ago, earning its reputation as one of the largest predators to ever swim the oceans. Some estimates suggest it could reach an astonishing length of 25 meters (82 feet). By reevaluating known specimens, researchers at the University of Portsmouth have determined that, although smaller, Liopleurodon ferox‘s massive skull still positions it as a formidable apex predator.
Artist’s impression of a pliosaur. Image credit: Megan Jacobs, University of Portsmouth.
According to Edward Bartlett and his team from the University of Portsmouth, “Liopleurodon ferox is a well-known Thalassophonian pliosaur from the Middle Jurassic (Callovian) Oxford Clay Formation in England and a comparable formation in northwest France.”
“It represents one of the earliest thalassophoniae, identified from a nearly complete skeleton,” they noted.
This reassessment has made Liopleurodon ferox a benchmark for systematic studies and size comparisons within the Thalassophoniae family. However, the complex taxonomic history stemming from the diagnosis of the holotype—a single canine tooth first described in 1873—has led to numerous Callovian-Tithonian pliosaurid specimens being assigned to this genus, resulting in a wide range of size estimates, from 6.39 meters to the mythical 25 meters featured in the 1999 BBC television series Walking with Dinosaurs.
In their study, Dr. Bartlett and colleagues calculated that Liopleurodon ferox measured between approximately 2.46 and 8.09 meters, with more complete skeletons averaging around 4.8 to 6 meters.
The researchers concluded that the average length for this species was probably closer to 5 meters—a fraction of the dramatic 25 meters.
“Our research marks the first comprehensive reassessment of all specimens linked to Liopleurodon ferox,” stated Dr. Bartlett. “By compiling all available material, we can finally deliver a solid estimate of its size and body proportions.”
While smaller than some iconic reconstructions, it remains a significant marine predator of the Jurassic Oxford Clay Sea.
In constructing the revised model, paleontologists relied on two well-preserved skeletons (one housed in Tübingen, Germany, and another at the Natural History Museum in London) alongside a complete skull used to adjust estimations of the skull’s proportions.
It was revealed that the skull constituted approximately 24% of the animal’s skeletal length, a considerably larger proportion than earlier estimates, indicating that Liopleurodon ferox was equipped to tackle relatively large prey compared to other contemporary pliosaurs.
Even reduced in size, Liopleurodon ferox still holds the title of the largest known creature from the Oxford Clay ecosystem.
However, the researchers hinted at an even more striking discovery. Several fossil fragments from the same rock layer appear to belong to a much larger pliosaur, with length estimates reaching up to 12.2 meters.
The true identity of this pliosaur remains a mystery, as these specimens lack the distinguishing characteristics required for species identification, but findings suggest that titanic creatures coexisted with Liopleurodon ferox in the mid-Jurassic oceans.
“This specimen, estimated between 7.02 and 12.2 meters, provides evidence that pliosaur gigantism (greater than 10 meters) evolved during the late Middle Jurassic,” the scientists concluded.
These findings will be published in the Journal of Vertebrate Paleontology.
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Edward O. Bartlett et al. “Re-evaluating the Body Size of Mid-Jurassic Pliosaurs: Liopleurodon ferox Sauvage, 1873.” Journal of Vertebrate Paleontology, published online on July 16, 2026. doi: 10.1080/02724634.2026.2691149
Source: www.sci.news
