Object of the Month – June 2025
Fossilised vertebra from a pliosaur’s backbone
At the museum, we usually see ichthyosaur vertebrae, which are quite small, flat and round – often compared to an ice hockey puck, with a dish-shaped hollow on both sides. This pliosaur vertebra is much bigger and more strongly built.
The difference in shape is down to the animals’ different swimming styles. Ichthyosaurs had a flexible backbone with lots of small vertebrae, as they moved their tails side-to-side to swim, like sharks. Pliosaurs were heavy-bodied animals which swam using large flippers, like turtles, and did not need such a flexible backbone. Ichthyosaurs and pliosaurs existed together alongside dinosaurs but belonged to their own groups of reptiles, distinct from each other and from dinosaurs.
Most species of pliosaur that lived around what is now Europe were around 10 metres long and would have weighed over 12 tons, about the same as two large male African elephants. Some species of pliosaur grew to 15 metres long.
During certain parts of the Jurassic Period (201-143 million years ago), pliosaurs were the top ocean predators. With short necks and long heads, like a crocodile, they used powerful jaws with sharp teeth to catch and eat fish, sharks and even ichthyosaurs.
Pliosaur fossils are not known from the local area, so if it was found nearby it is almost certainly an ‘erratic’, meaning that it was brought here from somewhere else. In our area, most erratics were brought from the north by the glaciers and ice sheets that covered the area over 400,000 years ago.
By Mario Lanzas – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=83865768
Elephant By Bernard DUPONT from FRANCE – African Elephant (Loxodonta africana) male, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=40724295
