Palaeontologists have turned to a large flightless bird, the cassowary, to help explain a structure found on a newly discovered dinosaur. Unearthed in China, Corythoraptor jacobsi is a new species of oviraptor that had a distinctive head crest, not unlike the cassowaries alive today.
To many, the flightless cassowary stalking the rainforests of northern Australia and Papua New Guinea are as close to a dinosaur as any living creature can get (well ok, technically they are dinosaurs). With their fearsome clawed feet, bright blue featherless heads, and piercing red eyes, they truly look like prehistoric beasts.
But it is the bony casque that adorns the cassowary’s head that is of interest to the researchers who discovered this latest fossil dinosaur. This is because the oviraptor uncovered in China seems to have an incredibly similar structure, and they think that by comparing it to the composition of the casque in living cassowaries, they can gain insight into its function in a dinosaur that has been dead for tens of millions of years.
The researchers studied the inner structures of both the fossil dinosaur casque and the living cassowary version, and compared the two in a new study published in Scientific Reports. The structure in the cassowary is made up of an internal bony web of microtrabeculae that is then covered with a thin layer of keratin, the same substance that forms both our hair and fingernails. It is found on both males and females of the species.
In the fossil, they found a similar arrangement. The inside of the casque shows a honeycomb structure with slightly bigger holes, and evidence suggests that it too had a veneer of keratin. Such striking similarities allowed the scientists to speculate what the long-extinct dinosaur would have used its casque for, based on its living analogue.
There are a number of different functions that have been suggested for the casque in cassowaries. It seems likely, however, that the main function for the crest is one of sociosexual, being used in both visual and acoustic displays. The birds produce low-frequency vocalizations, and the bony structure may help to resonate the sound during courtship dances. This, paired with sexual selection, offers the most satisfactory explanation for the adornment in the dinosaur.
This latest fossil find, which is the seventh type of oviraptor discovered in the same region of China, significantly expands the morphological diversity seen within this group. It is also thought to be the first oviraptor to show a highly developed skull crest, so it provides an incredibly valuable insight into what the ecosystem was like during the Late Cretaceous, just before the asteroid struck some 66 million years ago.