Where are Pterosaur Tail Vanes Found?
Basal pterosaurs are often illustrated with tail vanes, but they are not found on many basal pterosaurs. Soft tissue preservation is rare. The Campylognathoides/Rhamphorhynchus clade had the most prominent tail vanes. Various Dorygnathus may have had something like a vane. It’s never clear. Sordes had some sort of tail expansion and Pterorhynchus did not have a single vane, per se, but several very short ones along the length. The tail vane seems to have coalesced from several smaller vanes, which, in turn, may have developed from specialized ptero-hairs seen on the tail of Cosesaurus.
Figure 1. Click to animate. Tail vane animation on the C5 specimen of Campylognathoides zitteli.
Tail Vane Usage
The tail vane has typically been considered a steering mechanism, but airplanes don’t steer with their tail (vertical stabilizer). That just produces a skid and lots of drag. To initiate a turn airplanes, birds and bats roll into a bank. Presumably pterosaurs did likewise. The tail vane would have worked like feathers on an arrow shaft, keeping the back of the tail in line with the line of least drag, in line with the body at all times, and all without effort.
Correlations
You might note that the most prominent tail vanes are also found in the clade with the longest wings in relation to their body size. In Campylognathoides and Rhamphorhynchus the wing tips extend far above their head. The tail itself was stiff, able to rise and fall tilting at its base. The same was true of the wings. They were stiff and able to fold and unfold at the metatarsophalangeal joint. Those are similar actions as seen from the side. That got me thinking.
The Metronome Hypothesis
What if the tail rose and fell like a metronome? The wings could open and fold in counterpoint. Together the three elements might have produced a secondary sexual behavior that attracted mates… or was just a way to relax.
Pure speculation. Enjoy the animation.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
The Pterosaur Heresies 