Characteristics and Behaviors of Pterosaurs
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Pterosaurs were not dinosaurs but were closely related, and existed for 150 million years beginning in the late Triassic period through the Jurassic and Cretaceous periods until eventually becoming extinct along with the rest of the earth’s population at what is now known as the KT boundary event. The KT boundary event was the mass extinction that occurred at some point in time between the Cretaceous (K) and the Tertiary (T). This is famous because it marks the end of the 160 million years of dinosaur life. The theory is that asteroid rock hit the earth and caused the mass extinction. 1
Pterosaurs are commonly thought to be ancestors of modern day birds, but this is not true, even though they resemble bird and even bats of today. Much has been debated over what kind of behaviors pterosaurs exhibited when they existed. Today, more is known of what they were like 150 million years ago. Pterosaurs existed as different kinds of flying creatures. Their sizes ranged from a wing span of 6 inches to 40 feet and had different shaped and sizes of skulls. The two major kinds of pterosaurs were rhamphorhynchoids and pterodactyls. 2 Rhamphorhynchoids were a smaller type of pterosaur and pterodactyls were larger and rarer in numbers.
Stereotypes and False Impressions
Many people once believed that pterosaurs were weak flyers, or at least the larger ones were. The idea was that they used their large wings to glide instead of flap like flying creatures. This is now known to be false. Pterosaurs were also thought to be dinosaurs with similar anatomical features. Studies have shown now though that since the pterosaurs were not flappers but active flyers, their hearts were similar to those of mammals with four chambers, needed for an active way of life, unlike reptiles. In the past century, pterosaurs fossils have been known to be found with fur, which leads scientists to believe that pterosaurs needed insulation to keep in heat which indicated pterosaurs were active like mammals and warm blooded. 1
Like many sea birds or birds who fish out of the water, it was thought that pterosaurs dove strait into the water to catch their meal. This is not the case. Because pterosaurs have been known to grow as large as 40 feet in length and it would be impossible for such a large creature with such frail frames to crash into the water and survive.
4 Lastly, pterosaurs are now thought to have walked with four legs instead of the originally thought two. The pterosaurs hind legs were not suited for bipedality, or movement using two limbs, instead the creatures were “plantigrade quadrupeds”, meaning they walked on all fours. 3
Main Physiological Focuses and Behaviors
Pterosaurs were commonly stereotyped as weak flyers as stated above. But recent studies have found they were flappers, not gliders. Pterosaurs wings were attached by an elongated digit on their claws. The flight membrane and muscle attachments connecting the digit to the arm, shoulder and chest bones can show that the wings were used for flapping. Wing spans of pterosaurs reached 40 feet, such as those on Hatzegopteryx, one of the largest pterosaur. 3 The wings of the pterosaur were also attached to its hind limbs so as to connect the arm to the legs. The bones of the pterosaurs were also hollow or “honeycombed” so to make them lighter and fly easier.1 This, in turn, makes it very rare to find well preserved pterosaur fossils due to their easily decomposable structure. The membranes of the pterosaurs wings were also very complex, even though they were very thin for flight purposes. The membranes consisted of blood vessels, fibrous tissue and small muscles. Because of this, the membrane is thought to have some sort of use regarding heat preservation within the body of the pterosaur.3
Legs and Claws
As stated before, the wings of pterosaurs connected the arms and the hind limbs of the creature. Contrary to original thought, pterosaurs did not walk on two legs, they walked on four. This caused the pterosaur to be constrained while on the ground, not able to move quickly with its limbs unless in the air. Studies show that pterosaurs did not evolve from biped dinosaurs or birds, but tree climbing reptiles that used four legs to move. The claws of the pterosaur are curled such as those of tree climbing creatures of the past and present.3 Claws of pterosaurs can be closely correlated to animals’ behaviors, such as a modern day bird like woodpeckers who have curved claws. This fact strengthens the argument that pterosaurs were climbing creatures as well as flying. The idea that the creatures lived in trees has been ruled out though. While studying the claws of pterosaurs, and comparing them to the claws of modern birds that walk upright and birds that cling, scientists have found that pterosaurs have a combination of both traits. The claws on the feet of the pterosaurs were similar to those of birds that walk on the ground where they are relatively flat. The claws of the hands of pterosaurs are similar to those of perching birds that cling to trees where they are relatively more curved.5 The curvature of the claws on the arms of pterosaurs is also an indication that they may have used their claws, not their beaks, to pull fish out of the water and hold on to, or kill, their prey.
The head of the pterosaur can inform scientists of many physiological and behavioral traits of the pterosaurs. The shape of the head can first explain how the pterosaurs caught its prey, if it didn’t use its claws. Some beaks of the pterosaur reached 2 feet long, with very sharp teeth aligning on the sides of the mouth with a “basket of teeth” at the end of the mouth which was used for catching fish right out of the water when flying parallel to the surface of the water.4 One genera of the pterosaurs was the Tapejara, which had no teeth but a very sharp pointed tip of its beak which may have been used for spearing fish in the water.3 Studying the skulls of pterosaurs, scientist have been able to hypothesize that the sight of pterosaurs was similar to that of binocular sight, where they could hone in on fish from far above the water. This is due to its downward sloping head and an enlarged neurological structure called floccolus, which is a lobe in the brain that has connections to eye and neck muscles. These connections work to stabilize and sharpen views of prey within the eyes.6 Head crest on certain kinds of pterosaurs also had effects on their behavior. The head crests could have been used to attract mates or repel rivals or attackers.7
Pterosaurs are very rare in full form or with quality bone structure due to their frail skeletons. Because of this, it is hard for researchers to find concrete information regarding the behavior and anatomy of these creatures. It is also hard to explain where they come from, or what they brought about in regards to evolution and ancestry. Fortunately, pterosaurs lived on almost every continent so their remains could technically be found almost anywhere in the world. Recent discoveries have been made in the past 20 years that continue to lead scientists in the right directions with regard to pterosaurs behaviors and anatomy, and with the increased knowledge that comes with every new find, pterosaurs might not be such a mystery of the past, in the near future.
1. Pterosaur website
2. World Book: Pterosaurs. World Book Inc. 2004
3. Martill, Dave M., Naish, Darren. Pterosaurs- a successful invasion of prehistoric skies. Biologist. Vol.50, Iss. 5, 2003.
4. Steiner, Chris. Original big bird, pterosaur makes debut at Garfield Park. Chicago Tribune. Dec. 19, 2003; pg4
5. Perkins, Sid. Curved claws hint at pterosaur habits. Science News. Oct. 26, 2002. Vol.162, Iss. 17; pg270
6. NSF Press Release 03-124. Not all aerial reptiles were level-headed. Oct. 29, 2003.
7. Viegas, Jen. Pterosaurs stranger than ever. Discovery News. Oct. 9, 2003.