On The Brains Of Ichthyosaurs

Ichthyosaur fossils were amongst the first to be recognised as the remains of creatures which had gone extinct. They hold a special place in the history of palaeontology as such. Since their discovery in the early 19th century by Mary Anning in the cliffs of the Jurassic Coast, ichthyosaur research has flourished. As major components of Jurassic marine ecosystems, understanding their biology and ecology is vitally important to understanding how the Jurassic oceans functioned. Now a recent study has revealed the structure of their brains.

The digital reconstruction of the skull and brain of Hauffiopteryx typicus

Researchers, led by Ryan Marek from the University of Bristol, conducted CT scans of the skull of the ichthyosaur species Hauffiopteryx typicus and then utilised modelling software to create a digital reconstruction of the skull. Usually ichthyosaur specimens are crushed and so their skulls cannot be reliably reconstructed. The specimen used in the study, however, was almost complete and preserved in three dimensions, giving unprecedented access to the cranial anatomy of the species. 'The fossil is incredible,' said Marek. 'Its skull is in a good enough condition to use the latest visualisation techniques, allowing us to carry out work that’s never been done on ichthyosaurs before.'

By infilling the digital cavity within the skull, the researchers were able to create a model of the brain. They found enlarged optic lobes, which correspond to the specimen’s huge eyes and allowed it to see when diving to deeper, darker waters after deep dwelling species such as ammonites or squid.  The ichthyosaur also had an enlarged cerebellum, the part of the brain responsible for motor control, enabling it to be a highly mobile, visual predator. Additionally, the olfactory region, the area responsible for processing smell, was enlarged, adding to an already formidable sensory array.

'These results both confirm previous hypotheses on ichthyosaur sensory biology and also offer new insights into how these marine reptiles interacted with their environments,' said Dr Michael Benton from the University of Bristol. 'Perhaps the creatures relied more on their sense of smell than we previously thought.' As land dwelling mammals we sometimes forget that while our sense of smell cannot operate underwater, aquatic creatures have developed alternate sensory systems which perform the same function. A sense of smell in ichthyosaurs adds a whole new dimension to the Jurassic seas.