Debunkers dot Org

The best dinosaur book I’ve ever read. (OK, I know very well pterosaurs aren’t dinosaurs, but close enough for most purposes; besides if I said it was the best diapsid clade book I’ve ever read nobody would pay attention).

I’m supposed to know something about vertebrate paleontology (not that much, my own field was invertebrate paleoecology) but at least more than average. The trouble is a variant of the Red Queen Hypothesis; you have to keep learning as fast as you can just to break even and if you want to get ahead you have to learn even faster. Thus a lot of my vertebrate paleontology knowledge comes from Romer’s Vertebrate Paleontology, and now everything I learned out of that book is wrong. It’s wonderful.

At any rate, the 40-year old view of pterosaurs is that they were clumsy fliers (sometimes it was doubted that they could fly at all, and were just gliders), and that they were absolutely helpless on the ground. Thanks to the discovery of exquisitely preserved fossils in Brazil, Kazakhstan, and China, it’s now know that pterosaur wings were vastly more sophisticated than simple flaps of skin. The mystery was how an animal that depended entirely on a single finger to support its wing could actually develop any flight power. The answer turns out that the wing was a lot stronger than thought because of internal stiffening fibers and muscles. The muscles within the wing were presumably able to change the shape of local areas on the wing, and casts of pterosaur brains support this – the muscle control area is much larger than in similar reptiles. It’s also know now that a mysterious bone (a modified wrist bone) controlled a flap of skin on the leading edge of the wing (the propatagium, if you’re in to that sort of thing), allowing it to act like leading-edge slats on high performance aircraft. Similarly, the tailed pterosaurs (rhamphorhynchoids) had a extensive “wing” connecting the hind legs but not attached to the tail. The tailless pterosaurs (pterodactyloids) did not have the trailing “wing”, but did have webbed hind feet that could aid in maneuver. Pterosaur fossils are found hundreds of miles from the nearest paleoland, showing an albatross-like capability for sustained ocean flight.

Pterosaurs also had “hair”. Hair is in quotes there because it’s definitely not mammalian hair; it grows from the epidermis instead of the dermis and individual hairs are not hollow like they are in mammals. They had extensively pneumatized bones, like birds, suggesting an efficient breathing system (I have one question about this; author David Unwin says pterosaurs could not have functioned with the lung-inflation system of lizards or crocodiles. This is certainly true for lizards, which use rib motion to breathe, but crocodiles have a hepatic piston which is as effective as the mammalian diaphragm and bats fly just fine). Finally, the pterodactyloid pterosaurs seem to have been able to walk just fine; they probably looked rather odd doing it, but the wing finger folded backwards to allow the “hand” to make contact with the ground. This is one of the cases where once you know what you’re looking for they’re all over the place; pterosaur tracks were first noticed in 1957 but nobody had any idea what they were until the last few years; now there are full fledged pterosaur trackways, not only foot and handprints but peck marks where wading pterosaurs probed for marine invertebrates. They seem to have been able to run – that’s how they took off, building up speed on four legs, switching to two while the wings unfolded, and jumping with the hind feet to get airborne.

The organization and content of the book strike a near-perfect balance between technical details and fine drawings and references, and pretty pictures, making it just as interesting to the six-year old dinosaur fanatic and those with more advanced interests. There a full and double-page color plates, and Unwin has a dry sense of humor – the illustration of a pterosaur on its way to being fossilized in Solnhofen lagoon is: “It’s not pining, it’s passed on. This Pterodactylus is no more. It has ceased to be. It’s expired and gone to meet its maker. This is a late Pterodactylus*. It’s a stiff. Bereft of life, it rests in peace. It’s rung down the curtain and joined the choir invisible. This is an ex-Pterodactylus”.

*Not true; it’s Jurassic. A late Pterodactylus would be Cretaceous.

"a near-perfect balance between technical details and fine drawings and references, and pretty pictures"

Have you seen the pictures in The Greatest Show on Earth by Richard Dawkins?

Unfortunately there are too many books (or was it girls) and too little time.

Nope, haven't. Will check.



The book problem I've got. Not the other one.

I have a precocious 12-year-old he-sprog who sometimes thinks of being a paleontologist. Is this one likely to be too much for him?

I am wondering if it is not the albatross but the goose that the pterosaur resembles.

While watching some Canadian geese one day, it occurred to me that the goose's airframe is aerodynamically unstable. Because of its long neck, the center of pressure is ahead of the center of mass. This means that any little perturbation in its flight will cause the goose to veer off course.

This instability can be overcome by an active control system, as is done in some fighter planes. The problem is that an active control system requires more energy. Considering the distances that geese fly, this could be significant.

As it turns out, there is a good reason for the long neck. When flying in formation, having an instrument package out in front makes it easier to find the sweet spot in the airflow of the next ahead. The savings in energy probably more than compensate for the inefficient airframe.

I seem to remember pterdactyls (don't know if these are different from pterosaurs) having a long neck and no tail, just like a goose. They also had a crest on their head that would make them even more unstable. It would seem that, with a similar airframe, they would engage in formation flying as well. This might also mean that they were migratory, just like Canadian geese.

It's been a long time since I was 12 - but I think a precocious 12-year-old could probably handled it.

Hmmm. Interesting idea.

Pterosaurs are the overall winged reptile thingies, which divide into:

Rhamphorhychoids which show up first and have tails, and

Pterodactyloids which show up a little later and are tailless.

Funny thing about the necks. Studies on joint articulation suggest that all of the long-necked dinosaurs and dinosaur-like creatures that had long necks (sauropods, pleisiosaurs, pterosaurs) did not have to much neck flexibility. Older illustrations often use the bird analogy and show pterosaurs flying with a bend in the neck:



(that image also shows additional finger bones in the wings, which aren't there).

but it seems like like the neck had nowhere near enough flexibility to adopt a heron-like bend like that. What's more, what flexibility it did have was limited to the vertical plane; a pterosaur might ahve been able to bend the next enough to see backward between it's legs but couldn't do significant side to side movement.

Another interesting thing is that there are (apparently) no flightless pterosaurs, while there are flightless birds in abundance. There are also no small pterosaur species, although there are plenty of small individuals all the fossils thought to be small species now appear to be early growth stages of animals that would have had a minimum 1 meter and a maximum 10 meter wingspan as adults. The was a niche for small flying vertebrates but it was occupied by juvenile ptersaurs, not by small mature ones.

This seems consistent with aircraft design. The Wright brothers put vertical control surfaces at the front of their aircraft but kept the horizontal control surfaces at the back. Other aircraft designers have occasionally put vertical controls near the front of the aircraft but they have never put horizontal ones there.

Not being able to move its head or neck from side to side reduces the problem of maintaining course. Vertical motion would cause changes in elevation. These are probably not as critical since they would occur normally during flight anyway.

Saab Viggen
RAF Typhoon
Mirage
Kfir
Rafale
MacCready's man powered aircraft in the Seattle Museum of Flight

Those are just off the top of my head

You may want to review the Wright flyer again. I think your memory is reversed.

That picture also doesn't show the propatagium, which should cross the space between the hand and the neck where the wing is cranked backwards. Pterosaurs presumably did most of their maneuvering by changing the shape of the wings using the propatagium and interwing muscles.

Unwin argues that pterosaurs were the most successful flying vertebrates, having lasted much longer than bats and at least as long as birds (unless the Triassic Protoavis really is a bird). They certainly produced the largest flying organism (this is Quetzalcoatlus, there's reportedly an even larger pterosaur from Rumania. Aerodynamic studies suggest a 15-meter wingspan might be possible):



(Once again the neck is given too much flexibility and there's no way the animal could stand on its hind legs more than momentarily during take-off and landing. Also most of the reconstruction is speculative; IIRC only skeletal fragments are known).