A word in your ear, but make it snappy

Posted on Monday 28th July 2014

Crocodile skullCrocodiles usually conjure images of sharp teeth and powerful jaws – but they are not famous for their hearing.

However this could all change as new research sheds light on the reptiles’ ears, showcasing their evolution from the reign of the dinosaurs to the modern era.

Dr Felipe Montefeltro is undertaking research into fossilised crocodyliforms at the University of Birmingham as part of a three-month postdoctoral fellowship.

His work could provide clues as to why the reptiles have survived for so long while other creatures such as dinosaurs died out.

Dr Montefeltro’s research will see him dissect ears from existing crocodilians to understand their structures.

He will then compare information from existing species to as many fossil groups as possible to investigate the evolutionary implications.

Dr Montefeltro will use computed tomography (CT) to virtually peer inside fossil skulls and examine details of the ear anatomy that would otherwise be inaccessible.

He has also gained unprecedented access to the CT scan of a superbly preserved aquatic crocodilian skull belonging to London’s Natural History Museum.

The habitats of crocodilians have changed throughout time as they have shifted from aquatic to terrestrial environments and vice-versa.

A vital aid for hunting and communication

Dr Montefeltro’s research suggests that water and land-based crocodilians relied on very different types of hearing.

Modern, semi-aquatic crocodilians depend heavily on their hearing for hunting and communication. Their ears are unique among vertebrates, as their tympanic membranes are concealed by flat flaps that can be raised or lowered by muscles.

Crocodiles vocalise when in distress and during aggressive behaviour, yet the reception of underwater sounds is also important for them in social communication.

Along with birds, crocodilians are the only living representatives of the archosaurs; a group which includes dinosaurs and pterosaurs.

Some 200 million years ago crocodiles roamed Dr Montefeltro’s native Brazil and a plethora of ancient crocodilian species are waiting to be discovered in his homeland.

Dr Montefeltro hopes new discoveries in Brazil will feed into his research as they are uncovered. He returns to Brazil later this month to continue his work at São Paulo State University, where he is a postdoctoral researcher.

Dr Montefeltro said: "Crocodilians first appeared more than 200 million years ago and during this long history many subgroups have shifted from terrestrial to aquatic habitats and probably the other way around.

"Thus crocodilians are an attractive model to study evolution driven by habitat changes, such as the development of sensorial organs, like ears."

Dr Richard Butler, who has been working with Dr Montefeltro during his time in the UK, said: “Fossil crocodilians are fascinating because they were incredibly diverse, and occupied a whole range of environments and ecologies that we just don’t see today.

"Felipe’s research is providing us with important new insights into the biology and evolution of those extinct crocodilians that occupied extreme ecological niches."