Pliosaurs were a group of formidable marine reptiles that dominated ancient oceans from approximately 203 to 66 million years ago, during the Jurassic and Cretaceous periods. These air-breathing predators were widespread, with fossil evidence found across the globe. Their immense size was a defining characteristic, sparking scientific inquiry and public fascination.
How Scientists Estimate Pliosaur Size
Estimating the full body size of pliosaurs presents a challenge for paleontologists, as complete skeletons are rarely preserved. To overcome this, scientists rely on piecing together available fragmentary remains. A primary method uses skull length as a key indicator, applying a skull-to-body ratio derived from modern relatives like crocodiles or more complete plesiosaur skeletons.
Other methods involve scaling from individual vertebrae or flipper bones, which provide clues about overall body proportions. Because different methods, comparative animals, and reconstruction techniques are used, size estimates for the same pliosaur specimen can vary among studies. This variability highlights the ongoing refinement of paleontological understanding of these ancient giants.
The Giants of the Family
Liopleurodon is one of the most widely recognized pliosaurs, though its size has often been exaggerated in popular culture. The BBC’s 1999 documentary Walking with Dinosaurs depicted a 25-meter-long Liopleurodon, which sparked debate among paleontologists. Current scientific consensus indicates that Liopleurodon ferox likely reached 5 to 8 meters, with some larger estimates up to 10 meters.
Another well-known giant is Kronosaurus, an Early Cretaceous pliosaur found in Australia. Initial reconstructions, particularly of the Harvard skeleton, suggested lengths up to 13 meters. Later studies revealed these reconstructions may have included an inflated number of vertebrae, revising estimates to 9 to 11 meters.
The pliosaur informally dubbed “Predator X,” now formally named Pliosaurus funkei, generated excitement upon its discovery in Svalbard in 2008. Early media reports suggested an immense size, with estimates up to 15 meters. Scientific analysis revised its estimated length to between 10 and 13 meters, still making it one of the largest known pliosaurs.
A recent UK discovery of a 2-meter-long skull, belonging to Pliosaurus kevani, reinforces upper size estimates for the group. This skull suggests a total body length of 10 to 12 meters. Such finds provide insights into the maximum dimensions these powerful marine predators achieved.
Putting Pliosaur Size in Context
To appreciate the scale of a large pliosaur, comparisons to modern and prehistoric animals are helpful. A large pliosaur, around 12 meters long, would be roughly the same length as a modern school bus. Compared to a great white shark, which averages 4 to 6 meters, a large pliosaur would have been at least twice as long.
Pliosaurs also exceeded the size of orcas, which reach 5 to 8 meters. In prehistoric oceans, large pliosaurs were comparable in length to some mosasaurs, another group of marine reptiles, with some species reaching 12-13 meters. While often depicted as rivals to the later Megalodon, pliosaurs were similar in their role as apex predators. Megalodon was a shark and generally reached larger sizes than most pliosaurs. Despite their dimensions, pliosaurs were not the largest marine animals of all time; that title belongs to the blue whale, which can exceed 30 meters.