Pliosaurs had massive jaws, crushing teeth – and sensitive snouts. That is the conclusion of a study on an exceptionally preserved 2-metre-long fossil skull.
Pliosaurs were the top marine predators of the Jurassic, growing up to 12 metres long, but their biology is poorly understood because nothing quite like them is alive today.
Davide Foffa at the University of Bristol, UK, may now have added an important piece to the puzzle of how they detected prey. He has found channels in a pliosaur skull that probably contained nerves and blood vessels, suggesting that it had a well-developed sensory system extending to the tip of the snout.
Palaeontologists have long recognised that pliosaur skulls, like those of many other vertebrates, have small holes called foramina leading into the interior. In living species these connect to nerves. However, this is the first time anyone has been able to trace the networks inside a fossil.
Crocodile-like senses?
Using a custom-built CT scanner, Foffa traced channels filled with sediment and pyrite in a pliosaur skull unearthed in Dorset, UK. From the shape of the channels inside the skull, Foffa identified them as containing both the maxillary artery and the trigeminal nerve. These carry signals to and from the upper jaw and snout – including the skin and face.
It's unclear what the nerves sensed, but they may have responded to pressure like crocodile snouts, or to electrical fields, like sharks, says Foffa. "This kind of sensing system would have complemented the animals' vision in turbid water," he adds.
The most conservative interpretation is that the channels supplied blood and nerve connections to skin and soft tissue in the snout, says Adam Smith of the Nottingham Natural History Museum, UK, who wasn't involved in the research.
"It is quite likely the skull had sensitive and somewhat fleshy lip-like structures," he says, so pliosaur snouts had a sense of touch, and might also have responded to pressure or chemicals in the water. "Pliosaurs didn't have any other appendages to manipulate food or other items in their environment," he says, so a sensitive snout could help them hunt prey and manipulate food in the water.
"To get this much resolution out of the data is incredible," says Gareth Dyke of the University of Southampton, UK, who wasn't involved in the study but is using the scanner to study the shape of the pliosaur's brain.
Journal reference: Naturwissenschaften, DOI: 10.1007/s00114-014-1173-3
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