Mark P. Witton's Blog: Why we think giant pterosaurs could fly
Thursday, 31 May 2018
Why we think giant pterosaurs could fly
Giant azhdarchid pterosaur in flight. Images like this virtually always trigger discussions about the validity of giant pterosaur flight hypotheses.
Every so often the idea of flightless giant pterosaurs circulates in the press or on social media. It doesn't take much to ignite these discussions: a new giant pterosaur fossil, a PR event from a museum, or simply artwork<br>emphasising the size of giant flying reptiles will see someone, somewhere, questioning their flightworthiness. These suggestions are often made with strong conviction, to the extent of dismissing or even arguing with scientists who study pterosaur anatomy and biomechanics. After all, how can any sensible individual think that animals with 10 m wingspans and body masses hovering around 250 kg were capable of flight? At most they were gliders, or flighted as juveniles and flightless as adults, right?
Confession time: as someone actively involved in research and outreach on these animals, I often find these discussions frustrating, for two reasons. The first is that, among those who<br>actually study pterosaur functional morphology – that<br>is, those who make detailed observations and measurements of pterosaur fossils, compile<br>biomechanical data and use computer modelling to objectively test their<br>flight capacity – there is no controversy about the volant nature of these<br>animals, even at their maximum size. Peer-reviewed claims that pterosaurs were flightless are genuinely rare (perhaps limited to Sato et al. 2009; Henderson 2010 and Prentice et al. 2011 in the last decade) and have a consistent record of being flawed on some critical anatomical or functional detail (Witton and Habib 2010). There is no debate about giant pterosaur flight among those of us who study their fossils: the press and social media fuss about the topic is a genuine palaeontological nontroversy.
The second source of frustration is that, away from technical literature, discussions of giant pterosaur flight frequently suffer from major cases of Dunning-Kruger effect, especially when parties have knowledge of planes. I've experienced this a lot in my career, and not just in the wilds of social media: many of my TV and film consultancy jobs have required defending basic tenets of pterosaur anatomy - even their basic, there-for-all-to-see proportions preserved in articulated fossils - to folks who just can't or won't believe what the fossils show. Having a casual understanding of engine-driven man-made flying machines does not equate to knowing all there is about everything that has ever flown, but you would not know this from some conversations.
Our controversial giant azhdarchid friends Arambourgiania philadelphiae (middle) and Hatzegopteryx thambema (right), compared to a record-breaking giraffe and the Disacknowledgement.
Whether through naivety of palaeontological theory or unwillingness to accept good data, the lack of accessible overviews of current thinking on giant pterosaur flight probably fuels this ongoing nontroversy. What's needed, it seems, is a synthesis of modern ideas on giant pterosaur flight and justification for why pterosaur experts don't challenge this idea. I've attempted this below, including sufficient methodological detail and references so that anyone wanting to understand these ideas will have a useful jumping-off point, and to establish what needs to be overturned to challenge the null hypothesis of giant pterosaur locomotion. Our focus will be on the largest of all pterosaurs,<br>giant members of the clade Azhdarchidae, as they are the main subject of most<br>flightless claims (above). They are also among the most familiar giant pterosaurs,<br>their number including species such as Quetzalcoatlus and Hatzegopteryx. The general points made below pertain to all large pterosaurs, however.
Evidence from<br>comparative anatomy
Giant azhdarchids are invariably known from scant remains, sometimes a handful of fragments representing bones from across the skeleton or, in<br>the case of Quetzalcoatlus northropi,<br>an incomplete left wing (e.g. Lawson 1975; Frey and Martill 1996; Buffetaut et al. 2002; Vremir 2010; Martill and Moser 2018). Ordinarily, fragmentary remains are a barrier to<br>interpreting the locomotory strategies of extinct organisms but flighted<br>lifestyles adapt animal bodies to such an extreme degree that just a few bones can betray volant habits. It’s evident that even the largest<br>pterosaurs bore wing anatomy comparable to their smaller, incontrovertibly flightworthy relatives. Although<br>no complete giant wings are known, our fragments indicate similar linear<br>forelimb bone proportions to smaller azhdarchids. Their wing joints – including details<br>of their elbows, wrists and wing finger knuckle – are well understood, and indicate typical properties of pterosaur wing motion and function. We can make a number of predictions...