Dinosaurs and Birds...

[Touring Mars]

And what is the difference between a flying dinosaur and a pterosaur?

Pterosaurs and avian dinosaurs are two distinct groups that evolved separately, albeit ultimately from the same starting point. But the point in time where pterosaurs and (all) dinosaurs diverged was much further back in time than when the first avian dinosaurs appeared.

The fact that both pterosaurs and avian dinosaurs can fly doesn't mean that they are closely related, or that one is a consequence of the other... both acquired the power of flight completely independently, just like dolphins and sharks have very different evolutionary pasts but share many common characteristics.

The question of why no pterosaurs survived but some avian dinosaurs/birds did is a fascinating one, but viewed from the perspective that they were very, very different, it is perhaps not all that surprising.

 

[Dotini]

Pterosaur flight was probably far less efficient than bird flight, as the membranes could be damaged easily, particularly among trees, and their great size meant the largest ones were probably pretty damn heavy. They were also probably very slow-moving on the ground, as they would have to crawl on all fours with their wings folded round their backs, putting them at the mercy of predators.

There are some paradoxes and problems with your statement.
1) If pterosaurs were less efficient than birds, how could they have achieved much higher wing loadings, and flown more weight per wingspan than birds? See post #5 above.
2) If they were at the mercy of predators, how could they have flourished for ~160 million years?? See post #5 above.

 

[PeterJB]

There are some paradoxes and problems with your statement.
1) If pterosaurs were less efficient than birds, how could they have achieved much higher wing loadings, and flown more weight per wingspan than birds? See post #5 above.
2) If they were at the mercy of predators, how could they have flourished for ~160 million years?? See post #5 above.

1) I was pointing out that the design doesn't work as well as a birds because a large and very thin sheet of skin can get damaged a lot easier than a plumage of individual feathers. If the membrane is torn, that renders them incapable of sustained flight. As it stands we're still not sure about their weight. The largest could have weighed anywhere from 70 to 250 kilograms. I imagine getting something of that weight to fly for sustained periods would have been very difficult.

2) They were only at risk when on the ground, and since they would have spent virtually their entire lives in the air, they wouldn't have encountered this problem very often.

 

[Dotini]

1) I was pointing out that the design doesn't work as well as a birds because a large and very thin sheet of skin can get damaged a lot easier than a plumage of individual feathers. If the membrane is torn, that renders them incapable of sustained flight. As it stands we're still not sure about their weight. The largest could have weighed anywhere from 70 to 250 kilograms. I imagine getting something of that weight to fly for sustained periods would have been very difficult.

2) They were only at risk when on the ground, and since they would have spent virtually their entire lives in the air, they wouldn't have encountered this problem very often.

Dear Peter,
You say getting a pterosaur to fly for extended periods would be very difficult. Yet in the next breath you say they spent virtually their entire lives in the air.

I'm not sure about pterosaurs, but I don't think birds eat, sleep, or mate in the air. Neither do they lay, tend or hatch their eggs in the air.

 

[MrSulu]

It's a long way from a sauropod to a bird. Were they like any kind of bird with feathers? Perhaps these were the original dragons?

It's a long way, but they had a long time. 👍

Bronze/Iron age man could well assume it's a dragon.

Similar to the origin of Cyclops in Greek mythology could be from the unearthing of Mastodon and Mammoth skulls.

 

[CodeRedR51]

This was just posted on facebook, thought it should be posted in here.

http://www.iflscience.com/plants-an...d-tail-chickens-understand-dinosaur-movements

 

[PeterJB]

Dear Peter,
You say getting a pterosaur to fly for extended periods would be very difficult. Yet in the next breath you say they spent virtually their entire lives in the air.

I'm not sure about pterosaurs, but I don't think birds eat, sleep, or mate in the air. Neither do they lay, tend or hatch their eggs in the air.

Obviously then don't sleep or mate mid-flight. Feeding could be done mid-flight as they could grab fish from the water's edge for example. But when up and active I imagine they spent very little time on the ground, their bodies are designed almost entirely for flying.

The largest ones such as Quetzalcoatlus would have had difficulties that smaller ones would not have had due to their size and weight. They would have been a lot more cumbersome on the ground, and would have taken more effort to get themselves into the air in the first place.

 

[Grayfox]

The largest ones such as Quetzalcoatlus would have had difficulties that smaller ones would not have had due to their size and weight. They would have been a lot more cumbersome on the ground, and would have taken more effort to get themselves into the air in the first place.

They would have had to live on cliffs, some some birds these days or on the very top of cliffs

 

[Grand Prix]

While historically thought of as simple, leathery structures composed of skin, research has since shown that the wing membranes of pterosaurs were actually highly complex and dynamic structures suited to an active style of flight. The outer wings (from the tip to the elbow) were strengthened by closely spaced fibers called actinofibrils.[13] The actinofibrils themselves consisted of three distinct layers in the wing, forming a crisscross pattern when superimposed on one another. The actual function of the actinofibrils is unknown, as is the exact material from which they were made. Depending on their exact composition (keratin, muscle, elastic structures, etc.), they may have been stiffening or strengthening agents in the outer part of the wing.[14] The wing membranes also contained a thin layer of muscle, fibrous tissue, and a unique, complex circulatory system of looping blood vessels.[15]

As evidenced by hollow cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs (see Paleobiology section below) into the wing membrane itself.[16]

Which makes sense really, if pterosaurs were to achieve powered flight. I do not think the large specimens were necessarily cumbersome on the ground ether...

Pterosaurs' hip sockets are oriented facing slightly upwards, and the head of the femur (thigh bone) is only moderately inward facing, suggesting that pterosaurs had a semi-erect stance. It would have been possible to lift the thigh into a horizontal position during flight, as gliding lizards do.

There was considerable debate whether pterosaurs ambulated as quadrupeds or as bipeds. In the 1980s, paleontologist Kevin Padian suggested that smaller pterosaurs with longer hindlimbs, such as Dimorphodon, might have walked or even run bipedally, in addition to flying, like road runners.[41] However, a large number of pterosaur trackways were later found with a distinctive four-toed hind foot and three-toed front foot; these are the unmistakable prints of pterosaurs walking on all fours.[42][43]

Unlike most vertebrates, which walk on their toes with ankles held off the ground (digitigrade), fossil footprints show that pterosaurs stood with the entire foot in contact with the ground (plantigrade), in a manner similar to humans and bears. Footprints from azhdarchids show that at least some pterosaurs walked with an erect posture with their four limbs held almost vertically beneath the body, an energy-efficient stance used by most modern birds and mammals, rather than the sprawled limbs of modern reptiles.[25] [39]

For whatever reason though, they died out along with the dinosaurs and the marine reptiles. Perhaps birds were just better at adapting to the changing conditions during the mass extinction event?

It is probably very likely that the skeletons of dinosaurs and pterosaurs were indeed conceptualized as dragons by earlier civilizations. With different species found in different regions, and the nature of most fossilized specimens which tend to be incomplete, it would also explain why there were many types of dragons in ancient folkore, with most of them having a blend of traits associated with both dinosaurs and pterosaurs.

The fire-breathing part is likely a purely human-created fantasy.