Time for some more pterosaurs since we’ve been rather short of them on the Musings for a while. It seems pretty well know than the rhamphorhynchoids are blessed with a long tail, but also a vane of soft tissue at the end of this. However, beyond this, things get a bit murky and quite a lot is often illustrated with little reference to the actual fossils. This is a bit of a surprise as there is really very little known about them since so few are preserved so it shouldn’t be too hard to check up.
First off, what does have a tail vane? Quite a number are known for Rhamphorhynchus itself, and one specimen of Sordes has one as does Pterorhynchus, and, errr, that’s about it. Aside from the taxa listed above, it’s probably fairly safe to assume that most, if not all rhamphorhycnhoids had a tail vane. Pterosaurs are generally fairly conservative in their anatomy, and of course when it comes to soft tissues, these are rarely preserved and so have to be inferred from the few that do have them. Anuroganthids near certainly don’t have one however – not only does the short tail of this clade argue against this mechanically (since the vane is thought to have role in steering or steadying during flight) but we do have several specimens of anurognathids that preserve soft tissues in excellent condition with no sign of a vane.
Secondly, what lacks a vane? Anuroganthids aside, it’s generally considered that no pterodactyloids have one. Again the mechanics argument comes into play, but also again we do have a number (while admittedly very few) of pterodactyloid specimens with good soft tissues preserved and no trace of a tail vane. Given the huge change in character evolution from the rhamphorhynchoid to the pterodactyloid bodyplan (change in wing proportions, shape of the fifth toes and foot, tail length, skull elongation, neck elongation etc. etc.), this is pretty reasonable.
Tail vanes do turn up quite often in Rhamphorhynchus at least, and appear in cases where the wings are not preserved or not so well preserved which rather implies that they were fairly tough structures. Certainly they are more common and by inference, more robust than wing membranes or foot webbing at any rate (this also feeds back to the point about their absence in pterodactyloids – these should preserve if present). Structurally, all vanes have transverse banding across them which is presumably some form of reinforcement, though where the vanes are composed entirely of skin and interstitial tissues or have perhaps cartilage or anything else involved in their composition is not known.
But what shape were these vanes? If I had more time, that information would be appearing here, but I don’t so it won’t – more tomorrow.