Characters & Anatomy

Pteranodon skeletal plaque

Natural History Museum, London, UK

Like many flying animals, pterosaurs were very morphologically complex. The information below focuses on some of the most significant and unique aspects of pterosaur anatomy and physiology.

Wings & Flight * Skull & Diet * Legs & Terrestrial Locomotion * Hair & Endothermy


 

Flight in Pteranodon, from Hankin & Watson 1914

From The Pterosaur Database; used with permission.

Wings & Flight

Perhaps the most distinguishing feature of pterosaurs was the presence of wings. Pterosaur wings consisted of a membrane attached to the body and stretched along the length of the arm and a highly elongated fourth finger. The wing membrane itself was supported by protein fibres known as aktinofibrils. The exact structure of these fibres is unknown, but they appear to have had both a support and an aerodynamic function.

The vertebrae and long bones of some pterosaurs were hollow. This would have made the animals considerably lighter and therefore more effective flyers. Even with this reduction in weight, some of the larger pterosaurs may have had difficulties taking off from the ground. It has been suggested that large taxa may have leapt off of trees or cliffs to take off, but some aerodynamic studies suggest that even the largest species could have taken off from a running or flapping start (though see below for a discussion of running abilities in pterosaurs).

Like modern birds, pterosaurs had an enlarged sternum for the attachment of flight muscles. Many pterosaurs were probably strong flyers, but questions remain regarding giant taxa, such as Pteranodon and Quetzalcoatlus. Some research suggests that large pterosaurs were obligate gliders, while some suggest that they were capable of powered flight.

 

Pterodaustro

From The Pterosaur Database; used with permission

 Skull & Diet

Pterosaur skulls were generally long and narrow. Many taxa had sharp teeth, though some later pterosaurs were toothless (e.g. Pteranodon and Quetzalcoatlus). Long jaws and sharp teeth are characteristic of piscivorous animals, and it seems likely that most pterosaurs were fish-eaters. Some taxa appear to have evolved filter-feeding habits, most spectacularly the Cretaceous genus Pterodaustro: its long, curved jaw was lined with hundreds of bristle-like teeth that were probably used to strain microorganisms out of the water in a manner similar to modern flamingos. Other pterosaurs, such as Dimorphodon, appear to have eaten insects, shellfish, or other invertebrates. The diet of some of the giant toothless azhdarchids such as Quetzalcoatlus is still unknown, though it has been proposed that they were primarily scavengers.

Many pterosaur skulls supported large crests. Numerous theories have been proposed for these structures. Crests at the front of the jaw may have functioned as hydrofoils, helping reduce resistance and increase stabilisation as the jaws passed through the water to catch fish. It has been suggested that crests on the back of the head could have been used as rudders, stabilisers, or counterweights to long jaws. However, these structures are often highly sexually dimorphic, which strongly suggests that they were used as display structures.

 

Dimorphodon shown (probably incorrectly) in a bipedal pose

Bristol City Museum, Bristol, UK

 Legs & Terrestrial Locomotion

Unlike those of birds, the legs of pterosaurs were very short relative to their arms. As such, they were probably far less adept at terrestrial locomotion. It has been argued that pterosaurs were capable bipeds, but a suite of skeletal features suggests that this is not the case, and that pterosaurs were obligate quadrupeds. This interpretation has been supported by evidence from trackways.

It has also been suggested that at least some pterosaurs were able to swim, much in the manner of many living shorebirds. The recent discovery of unusual tracks in the Southwest United States lends some credence to this theory, as they seem to show scrape marks made by a pterosaur paddling in shallow water. There is, however, no evidence for diving behaviour in pterosaurs.

 

Sordes

From The Pterosaur Database; used with permission

 Hair & Endothermy

Pterosaurs were first described in the 19th Century, and even at that time many researchers considered them to be endothermic, or "warm-blooded," just as modern birds and bats are. Several bits of circumstantial evidence supported this theory, perhaps most importantly the evidence of rapid growth in pterosaur bones. More convincing proof of the endothermy hypothesis emerged in 1971, when the Russian paleontologist A.G. Sharov described a species he named Sordes pilosus - "Hairy Devil" - so named because the specimen was covered in a thick layer of a hair-like substance. Only animals that are capable of generating their own body heat have any use for hair, the function of which is to trap warmth escaping from the body. Due to this evidence, it is now widely accepted that pterosaurs were active, endothermic animals.



Author: John D. Orcutt

Last Updated: 11/2005

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