In the late 1700s, a most unusual fossil found its way to the Naturalienkabinett – more commonly known as a “cabinet of curiosities” – located inside the German palace of Charles Theodore. Uncovered at the Solnhofen limestone bed in Bavaria, this strange creature with long, flexible forearms baffled the Naturalienkabinett’s curator Cosimo Collini, who speculated that it may have been an amphibian since nothing like it had ever been seen on land.
By 1809, other scientists who had studied the fossil concluded that instead of coming from the sea it was native to the sky. French scientist Georges Cuvier went even further, declaring the species to be a flying reptile and named it Ptéro-Dactyl, which translates into “wing finger.”
Slightly over 200 years later, the American Museum of Natural History in New York City launched Pterosaurs: Flight in the Age of Dinosaurs, a traveling exhibit that premiered at the AMNH in April 2014 before embarking on a cross-country tour of the United States that included stops at the Carnegie Museum of Natural History in Pittsburgh and the Natural History Museum of Los Angeles.
“Despite persistently captivating our popular imagination, pterosaurs are among the least well-understood large animals from the age of dinosaurs,” Ellen Futter, American Museum president, explained when the exhibit made its New York debut. “In the past decade, however, there has been an explosion of pterosaur research and new fossil discoveries, including by scientists at the AMNH and the exhibition’s curatorial team. Showcasing scientifically accurate information, this exhibition presents these fascinating winged reptiles, compares them to both dinosaurs of yesteryear and modern-day birds and bats, and explores the biomechanics of pterosaur flight.”
The reasons that so little has been known about pterosaurs – the overall taxonomic order that includes pterodactyls – are many. First of all, pterosaurs were not dinosaurs as these winged reptiles evolved differently than the T. Rex and Brachiosaurus that roamed the land. Because they had developed the ability to fly, meanwhile, the bones of pterosaurs were hollow with paper-thin walls as opposed to the sturdier equivalents of dinosaurs. This means that far fewer pterosaurs were preserved as fossils as their bones were more delicate and unable to withstand the fossilization process.
While one might suspect that modern-day birds were descendants of pterosaurs, birds actually evolved from the few remaining dinosaurs that survived extinction. Pterosaurs were not as fortunate as the entire species was wiped out when a giant meteor hit the Yucatán Peninsula in the Gulf of Mexico, leading to the loss of three-quarters of life on Earth. Thus while paleontologists can study birds to help better understand dinosaurs, no correlating relatives exist today when it comes to pterosaurs.
Despite such restraints, the discovery of pterosaur fossils has steadily increased since that initial finding in the late 1700s. Mary Anning – who lived in the Dorset region of Southwest England during the early 1800s – was one of the most prolific fossil hunters of any era. Fossil beds within the cliffs along the English Channel provided a rich resource for Anning, and her discoveries included the first pterosaur found outside of Germany.
The resulting Dimorphodon macronyx was named by the controversial paleontologist Richard Owen to distinguish it from a Pterodactylus, which had a smaller skull and larger wings. As more fossils were found, meanwhile, a better understanding of pterosaur evolution developed as well. The earliest pterosaurs first appeared during the Triassic Period, for instance, and were relatively small with long tails and short necks.
By the time of the Jurassic Period, the opposite was true as pterosaurs had developed shorter tails and longer necks. The trend continued into the Cretaceous Period with the further addition of long, slender skulls and very long necks. Pterosaurs also evolved in size during this era, from that of a small bird that could fit into a human hand during the Triassic Period to the Quetzalcoatlus northropi of the Cretaceous, which reached sixteen feet in height when resting on all four limbs and had a wingspan similar to those of a small airplane.
While pterosaurs are one of only three vertebrates that developed the ability to fly, their evolution differed vastly from the other two. Modern day bats have long hand bones and fingers that support a thin, flexible membrane wing surface, while birds have smaller finger bones and a wing surface comprised of feathers.
Pterosaur hand bones were long like a bat but only the fourth finger stretched longer. The wing surface was likewise a membrane – just like a bat – but was stiff as opposed to flexible due to several layers of internal fibers not found in bats or birds.
Although paleontologists have uncovered a multitude of information about pterosaurs – including the fact that they hatched with fully developed wings and walked on all four limbs as opposed to their hind legs – there are still aspects of pterosaurs that are left to conjecture. How pterosaurs evolved into flying reptiles is one such question whose answer still eludes scientists, with three theories having been developed in recent years.
The first postulates that pterosaurs evolved from reptiles that ran on their hind legs and could generate lift by flapping their arms. Another hypothesizes suggests that tree-dwelling reptiles were pterosaur ancestors who developed the ability to fly by jumping to the ground in order catch prey or flee predators. The last theory likewise involves tree-dwellers but instead of jumping to the ground, these reptiles learned to leap from tree-to-tree.
Paleontologists are also uncertain about why so many pterosaurs had head crests in such a wide variety of shapes and sizes. The three dominant theories suggest that the crests might have been a way for pterosaurs to recognize members of their own individual species; as a way to attract sexual mates; and as a means to cool their bodies during the physical exertion required to fly. A fourth theory suggests that head crests were used for steering during flight but recent tests have found that such head movements would have created too much wind drag for the method to be effective.
Sixty-six million years ago, dinosaurs may have ruled the Earth but it was pterosaurs that claimed the sky as their domain. The Pterosaurs: Flight in the Age of Dinosaurs exhibit that the American Museum of Natural History launched in 2014 provided an overview of this dominance that not only explored pterosaurs themselves but the findings of paleontologists across the globe. Thanks to those efforts we now have a better understanding of these flying reptiles – extinct creatures from the past that continue to fascinate over 200 years since there existence was first discovered.
Anthony Letizia