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And now we come to the fourth and for now last coin featuring a prehistoric animal that many people think is a dinosaur but is not featuring Quetzalcoatlus northropi, one of the largest flying animals to ever live.
As is the case with many animals which a known only from fossils, we actually know very little about Quetzalcoatlus. We know that it could fly and that it had a wingspan from between 33 to 36 feet. We also know that it could move as a quadrupedally, as it is depicted on the coin. Aside from wingspan esitmates, other size estimates on Quetzalcoatlus are extremely difficult as there are no extant animals with a body plan similar to Quetzalcoatlus in any way. While some of its relatives had teeth, Quetzalcoatlus did not, instead having a long, spear-like toothless beak. This toothless beak initially led paleontologists to believe that Quetzalcoatlus was a predator of fish, but the knowledge that these animals were actually capable of walking has led to most researchers now considering Quetzalcoatlus as an apex predator in its ecosystem with hunting behaviors similar to large, predatory storks such as the Marabou Stork. Which makes this animal an absolute horror when you think about how Marabou Storks behave and you then scale them up to three times larger than they already are.
So, since this coin is in this part of the set, we’ve already established that Quetzalcoatlus is not a dinosaur. So, what is it then? Quetzalcoatlus is a Pterosaur, a type of flying reptile which existed alongside dinosaurs throughout the Mesozoic Era until their full extinction during the Cretaceous-Paleogene Extinction Event 66 million years ago. Pterosaurs are very interesting in that they are the earliest known flying vertebrates and that, unlike the other animals already discussed in this part of the set, they actually were relatively close relatives of dinosaurs though they were not dinosaurs themselves. Pterosaurs are not only reptiles, but they are also Archosaurs, making them close evolutionary cousins of both dinosaurs and crocodilians. Pterosaurs are also Avemetatarsalians, making them even more closely related to dinosaurs than crocodilians are, but in the great scheme of things that relationship is still somewhat distant.
Pterosaurs share some very interesting traits with dinosaurs. They had hollow bones, some of them were toothed while others were beaked and some of them also had a furry integument known as pycnofibers, which may have been homologous to feathers in theropods. The fact that pterosaurs completely died out in the Cretaceous-Paleogene Extinction also indicates that they were likely warm-blooded like dinosaurs are as well. However, the extinction of the pterosaurs is something of a mystery. It was initially thought that the end-Cretaceous Event took the pterosaurs because early birds and other flying non-avian theropods like enantiornitheans outcompeted the small-size pterosaurs, leaving only large bodied forms like Quetzalcoatlus by the Late Cretaceous.
As we already know, large bodied endotherms were the most vulnerable to the environmental stresses and food shortages during the Cretaceous-Paleogene Extinction and they were obliterated. However, recently discovered fossils indicate that there were small pterosaurs sharing the skies with flying theropods all the way to the very end of the Cretaceous, after which pterosaurs completely disappear from the fossil record. These discoveries make the extinction picture for pterosaurs much more complicated and mysterious as small pterosaurs would seem to have had many of the same advantages as smaller flying theropods in dealing with the conditions of the end-Cretaceous Event. However, none of them survived even though a few species of birds managed to make it through. The large pterosaurs, however, likely succumbed to the food shortages which took down other large endotherms, such as most of the dinosaurs and the aquatic mosasaurs.
While we’ll likely never know exactly why no small pterosaurs survived while a few of their flying theropod cousins managed to. It could be a question of geography. The fossil record seems to indicate that most of the dinosaurs that managed to survive the end-Cretaceous Event were located in the Southern Hemisphere, in what is now the continents of South America, Australia and Antarctica. South America, in particular, seems to have provided a refuge where a few communities of small, flying theropods could weather the storm. It’s possible that there were no small pterosaurs present in this refuge and that the areas where they did live were all heavily affected by the meteor impact, leading to their full extinction. It’s also possible that the few surviving birds had something about them which allowed them to outcompete any surviving small pterosaurs, leading to their demise. We already know that theropods are, as a general rule, very intelligent animals and that their advanced brains appeared early in their evolution. Pterosaur endocasts, which are rare but there are a few known, indicate that while pterosaur brains were complex (as would be required for a flying animal), they were not as complex as theropod brains. This makes losing the battle for scarce food resources in the earliest days of the Paleogene to surviving theropods a possible cause for the final extinction of pterosaurs. However, though there are many theories, we’ll likely never know why the small pterosaurs died out while a small number of small, flying dinosaurs survived to continue evolving throughout the Cenozoic.