Elvis, the curl-crested pterosaur
digital painting, 2023
see skull of Petrodactyle in situ
Hone, D.W., Lauer, R., Lauer, B., & Spindler, F. (2023): Petrodactyle wellnhoferi gen. et sp. nov.: A new and large ctenochasmatid pterosaur from the Late Jurassic of Germany. Palaeontologia Electronica, 26(2): a25.
I knew Elvis from photos: the only fossil of this pterosaur, which has meanwhile been named as Petrodactyle. I also knew that it was one of the largest Jurassic representatives of which more than a few fragments are known – in this case even a nearly complete skeleton. However, standing in front of the specimen in real life was once again very impressive. Especially because I can visualise a breathing, twitching animal after even a few moments. This one is truly exotic, and with a wingspan of over two metres, it is significantly larger than most of today's birds.
The bony crest, whose fibres are so noticeably curved forwards in Petrodactyle, is particularly large. It is now known that this diverse organ was present in almost all subgroups of pterosaurs, from the earliest species from the Triassic onwards. Frequently they are shaped like narrow bonnets, sometimes as bars. They are often bony, sometimes made of horn or other soft tissue. In the case of Petrodactyle, we can assume that it was a composite of both. This is because several comparative finds indicate additional skin discs, for which such a bony crest only represents the basal support.
There is a pterosaur, geologically somewhat older in the Jurassic, which apparently carried no crest at all, but an egg, ready to be laid. We can therefore assume that the many skulls without crests were females, or not yet mature. Of course, there could also have been species without any head ornaments at all. But as common as these are, this would be the more unlikely assumption for most types of pterosaurs.
So, if the bony crests are sexually dimorphic, they probably served for social signalling: Coloured or patterned, or just nice and big, they were intended to intimidate rival males, but really get the females excited. Additionally, there is the handicap effect: such combs – and the painting here is by no means an exaggeration! – must inevitably have presented a difficulty in the crosswind. So if an ornamental feature actually represents an obstacle that a potent male pays for with time, strength or safety, then it shows all the more that he can cope with such challenges. A classic example today is the peacock: it flies more poorly with its long feather train and attracts the attention of every tiger. That's how you recognise the tough guys. It proves the fitness of the genes.
In many animal groups, a correlation has been observed between head ornaments, or social signalling in general, and group life. However, there is no evidence to date that pterosaurs took particularly good care of their babies. They were extremely quick to fledge and definitely not altricial, which makes an answer so difficult. A small Jurassic pterosaur with a healed leg fracture can be discussed as an argument that conspecifics must have fed it. This is based on the many healed fractures of sabre-toothed cats from the Pleistocene tar pits of Los Angeles. It is certainly possible. But when I look at wounded birds, they sometimes manage quite well on their own. There was this clip of the one-legged sandpiper that was as fast as the whole flock around it, but it had to find its own food...
And once again a single fossil has triggered a whole little mind safari through palaeontology! And now hear the sound of the sea - don't scare the Petrodactyle away, it's a rare sighting!