Rhamphorhynchoidea

The earliest-known pterosaurs were already advanced flyers by the Late Triassic period, some 190 million years ago. They flourished worldwide until the end of the Jurassic, when they became extinct.

name: Eudimorphodon time: Late Triassic locality: Europe (Italy) size: 2 ft 5 in/75 cm wingspan

Eudimorphodon is well known from remains preserved in marine rocks of northern Italy. It was a typical rham-phorhynch, with a short neck and a bony tail, which made up about half the animal's length of 2ft 4in/70cm. The head was large but lightweight, owing to the 2 pairs of openings in its diapsid skull (see p. 61).

The membranous flaps of skin that made up Eudimorphodon's wings were attached to the enormously elongated fourth finger of each hand. This finger was composed of 4 extra-long finger bones (phalanges), and was attached to the wrist by an elongated hand bone (metacarpal). The wings joined the body on each side at the thighs. Another small flying membrane ran from the bones of each wrist to the base of the neck.

Eudimorphodon was evidently an active flyer, capable of flapping its wings like a modern bird. The sternum, or breastbone, was developed into a broad, flattened plate, to which the powerful flight muscles attached, although the keel was low in comparison to the great keel of modern flying birds.

The long tail would have been held out rigidly during flight, its vertebrae lashed together by bony tendons into an inflexible rod, which counterbalanced the animal's comparatively heavy fore-quarters. As in many other rhamphorhynchs, there was a vertical, diamond-shaped flap at the tip of the tail, which most probably functioned as a rudder during flight.

The short jaws of Eudimorphodon were armed with 2 kinds of teeth. There were long, peglike teeth at the front of the mouth, and short, broad teeth at the back. This pterosaur probably flew low over the sea, its large eyes trained on the surface to spot its fish prey.

name: Dimorphodon time: Early Jurassic locality: Europe (England) size: 4 ft/1.2 m wingspan

Dimorphodon had the disproportionately large head typical of the rhamphorhynchs. It measured about 8in/20cm long, about a quarter of the total body length. But it had a remarkable puffinlike shape, deep and narrow, unlike that of its relatives. There seems to be no structural reason for this, since the teeth show that the jaws were simple. Perhaps the shape of the head represents some type of display structure for territorial or courtship behavior, like the showy heads of modern hornbills or toucans.

The walking method of pterosaurs has long been debated. Based on studies of Dimorphodon's hips and legs, some paleontologists believe that they had an erect, birdlike stance, with the legs set directly under the body, so that they could run on their toes quite quickly.

But finds of other types of pterosaur in 1986 indicate that perhaps Dimorphodon was an exception. These recent finds show that the upper leg bones were splayed out sideways from the hips, which could only have resulted in a clumsy, sprawling, batlike gait. It is suggested that pterosaurs spent much of their time hanging from cliffs and branches, using their clawed fingers and toes to reach these vantage points, from which they could then launch themselves.

name: Rhamphorhynchus time: Late Jurassic locality: Europe (Germany) and

Africa (Tanzania) size: 3 ft 3 in/1 m wingspan This pterosaur is particularly well known because it was preserved in the fine-grained limestones of Solnhofen in southern Germany. These limestones also yielded specimens of the earliest-

name: Scaphognathus time: Late Jurassic locality: Europe (England) size: 3 ft 3 in/1 m wingspan

One specimen of this typical rhampho-rhynch was preserved in such a way that its brain cavity could be studied. The size of this cavity revealed that Scaphognathus had a much larger brain relative to that of other similar-sized reptiles. It was almost as large as that of a modern bird.

Paleontologists have studied the relative sizes of the areas of the brain that controlled various senses. They conclude that Scaphognathus, and presumably all its relatives, had excellent eyesight, but a poor sense of smell. The cerebellum and associated lobes in the brain were highly developed, indicating agility of movement, which supports the theory that small pterosaurs were active flappers, like small modern birds.

rhamphorhymj

Scaphognathus

scaphognathus dimorphodon known bird, Archaeopteryx, complete with impressions of its feathers stamped into the rocks (see p. 176).

Similarly, the fine structure of Rhamphorhynchus' wings, made of membranous skin, has been preserved in these limestones. Microscopic study reveals that thin fibers ran from the front to the back of the wings, strengthening them — comparable to the radiating fingers that support the wings of a modern bat.

Rhamphorhynchus had long, narrow jaws filled with sharp teeth that pointed outward, like the barbs on a fishing spear. Fish remains have been found in the crop and stomach of some specimens; its habit was probably to skim over the water, its long tail held out for stability, snapping up fish in its jaws.

scaphognathus dimorphodon rhamphorhymj

Dimorphodon

pterodaustro quetzalcoatlus pteranodon cearadactylus dsungaripterus pterodactylus name: Sordes time: Late Jurassic locality: Asia (Kazakhstan SSR) size: 1 ft 6 in/50 cm wingspan

For a long time, paleontologists have argued about whether carnivorous dinosaurs and pterosaurs were endo-thermic or warm-blooded. The active, predatory life of both these types of ruling reptile would suggest that they had a high metabolic rate, and could control their body temperature.

To support this theory, some paleontologists have suggested that both dinosaurs and pterosaurs were covered in an insulating layer of down or hair, as an aid to regulating their body temperature. In the case of dinosaurs, no such evidence has ever been found. But a find in 1971 seemed to confirm the theory for pterosaurs. A specimen of Sordes pilosus was discovered, southeast of the Urals. Its body appeared, from the impressions in the fine-grained deposits, to be covered in a pelt of dense fur. The tail and wings were naked.

Some paleontologists, however, have questioned this find, pointing out that the fine-grained limestones of southern Germany have yielded the best-preserved pterosaurs, and that no impressions of fur have ever been found in any of these specimens.

name: Anurognathus time: Late Jurassic locality: Europe (Germany) size: 1 ft/30 cm wingspan

This comparatively small rhampho-rhynch had a deep, narrow head with short jaws, which were filled with strong, peglike teeth. This could suggest that it lived on a diet of insects. Unlike other rhamphorhynchs, it had a short tail, and this feature, combined with the small body size, would have made it highly maneuverable in flight after its fast-moving prey.

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