Rhamphorynchoids

The rhamphorynchoids were the earliest and most primitive of the pterosaurs. Yet these had become already advanced fliers by Upper Triassic times (ca. 228 mya). Eudimorphodon (Figs. 45,56; Sect. 6.1) is a well-known example. Its long tail would have been held out rigidly during flight, counterbalancing the

Peteinosaurus
■ Fig. 56. Left Peteinosaurus (Rhamphorhynchoidea; Upper Triassic; wingspan ca. 60 cm). Right Eudimorphodon (Rhamphorhynchoidea; Upper Triassic; wingspan ca. 1 m)

comparatively heavy head and neck. The vertical diamond-shaped flap at the end probably served as a rudder for steering as the animal flew low over the sea searching for the fishes on which it preyed. The jaws were fairly short and the teeth were of two kinds. Those in front were long and peg-like, while the back teeth were short and broad. In Peteinosaurus (Fig. 56), which existed roughly contemporaneously but was rather smaller, a large number of small teeth were set behind a few big ones in front. Peteinosaurus was even more primitive than Eudimorphodon and probably insectivorous. Its wings were short - only twice as long as the hind legs. In other pterosaurs they were nearly three times longer. Its successor, Dimorphodon (Fig. 57) from the Lower Jurassic of Europe, had a disproportionately large head, as was typical of the rhamphorhynchoids. The skull was uniquely shaped, like that of a puffin, and was about a quarter as long as the body. The short, sharp teeth may have been an adaptation to a piscivorous diet; while the deep, narrow head could possibly have been used in territorial and courtship display.

Rhamphorhynchus (Fig. 58), from the Late Jurassic of Europe and Africa, has yielded some exceptionally well-preserved fossils of several species in the fine-grained limestone strata of Solnhofen in southern Germany. Microscope study of the wings reveals that thin fibres ran between the fronts and the backs of the wings and strengthened them as do the radiating fingers that support the wings of bats. (These fibres were already mentioned in Sect. 6.3.) The jaws of Rhamphorhynchus were long and narrow, and its sharp teeth pointed outwards like the barbs of a fishing spear. Their function is confirmed by the pres-

Lizard Mesozoic
■ Fig. 57. Dimorphodon (Rhamphorhynchoidea; Lower Jurassic; wingspan ca.1.2 m). (After Augusta 1961)

ence of fish remains in the crop and stomach of some fossil specimens. Rhamphorhynchus probably skimmed over the water mopping up fishes, whilst its long tail was held out for stability (Palmer 1999). It would also have poked its elongated snout into the burrows of polychaete worms to extract their occupants (Bakker 1987).

Also from the Late Jurassic of Europe was Scaphognathus. Although similar in size to Rhamphorhynchus, this genus had a shorter head and long teeth, while the tips of its jaws were blunted. The skull of one specimen has been sufficiently well preserved for the brain cavity to be studied. This was found to be proportionately much larger than that of most other reptiles of similar size -almost as large as that of a modern bird. The cerebellum and associated lobes of the brain were very well developed, which indicates that the animal would have been extremely agile. It apparently had excellent eyesight but a poor sense of smell (Langston 1981). Scaphognathus (Fig. 59) was a close relation of Sordes (Fig. 52, Sect. 6.3). Anurognathus (Fig. 59) differed from other known rhamphorhynchoids in having a relatively short tail. In this it foreshadowed the Pterodactyloidea, although in other respects its body proportions were

Rhamphorhynchoidea

■ Fig. 59. Left Anurognathus (Rhamphorhynchoidea; Upper Jurassic; wingspan ca. 30 cm). Right Scaphognathus (Rhamphorhynchoidea; Upper Jurassic; wingspan ca. 1 m). (After Wellnhofer 1991)

Preondactylus

■ Fig. 60a-i. Heads of rhamphorhynchoid pterosaurs (not to scale). a Eudimorphodon (Upper Triassic), b Preondactylus (Upper Triassic), c Peteinosaurus (Upper Triassic), d Dimorphodon (Lower Jurassic), e Dorygnathus (Lower Jurassic), f Campylognathoides (Lower Jurassic), g Rham-phorhynchus (Upper Jurassic), h Scaphognathus (Upper Jurassic), i Anurognathus (Upper Jurassic). (Mostly after Wellnhofer 1991)

■ Fig. 60a-i. Heads of rhamphorhynchoid pterosaurs (not to scale). a Eudimorphodon (Upper Triassic), b Preondactylus (Upper Triassic), c Peteinosaurus (Upper Triassic), d Dimorphodon (Lower Jurassic), e Dorygnathus (Lower Jurassic), f Campylognathoides (Lower Jurassic), g Rham-phorhynchus (Upper Jurassic), h Scaphognathus (Upper Jurassic), i Anurognathus (Upper Jurassic). (Mostly after Wellnhofer 1991)

similar to those of the Rhamphorynchoidea; and it was contemporary with Scaphognathus. Anurognathus was a very small, slender pterosaur with unusually long wings and a short, deep head. Its teeth were peg-like and it was almost certainly insectivorous. Having dispensed with a long tail, it would have been extremely manoeuverable, snapping up flying insects on the wing.

Much can be learned about the animals that possess them by the study of skulls and teeth. In Fig. 60, reconstructions are shown of the heads of several rhamphorhynchoid pterosaurs. Eudimorphodon (Fig. 60a) was a fish-eater as we have seen. Preondactylus (Fig. 60b), among the earliest rhamphorhyn-choids in the fossil record, may have been ancestral to Dorygnathus (Fig. 60e). It is not clear whether it fed on insects or on small fishes. A fossilised gastric pellet of its accumulated bones is interpreted as having been spewed up by a large predatory fish. This could have caught the pterosaur as it was skimming over the surface of the water or, alternatively, the animal might already have drowned.

Peteinosaurus (Fig. 60c) was smaller than Eudimorphodon. Its dentition consisted of large anterior fangs followed by a series of smaller tusks. It might have caught insects while on the wing, as bats do. Dimorphodon (Fig. 60d) had long, sharp, curving front teeth. These pointed directly upward from the lower jaw and forwards from the upper. The animal's strong bite must have been delivered by a rapid snap of the jaws as it skimmed over the water, snatching fishes from the surface. In addition, however, the neck of Dimorphodon, unlike that of many other rhamphorhynchoids, was constructed in such a way that this pterosaur could deliver rapid lunges to grab at prey. Extra large fishes and squids could have been swallowed because, at the midpoint of the lower jaws, there was a zone of weakness. This might have allowed the jaws to bow outwards so that the meal could slip down the throat of the animal (Bakker 1987).

Campylognathoides (Fig. 60f) had the teeth of a piscivore, whilst its unusually large eyes suggest that it might have been adapted for nocturnal hunting. Rhamphorhynchus (Fig. 60g) was also a fish-eater, as mentioned earlier. Fossils of several species in this genus, displaying a range of sizes, have been discovered. Fish and squid can detect the dive of a pelican or a puffin just before the bird strikes the water and, consequently, scatter in all directions at the last moment. The hunting methods of the pterosaurs evolved to maximise the rapidity of their strike. Some responded like Dimorphodon. In Rhamphorhynchus, the S-shape of the neck was accentuated so that the head could be coiled tightly against the shoulders and then shot forward to capture prey. As already mentioned, the jaws and teeth were shaped like fishing spears; even the tips of the jaws were tapered to sharp points which could be used to impale the prey, whose struggles served only to drive the barb-like teeth into its body (Bakker 1987).

Finally, Scaphognathus (Fig. 60h) had strong piscivorous fangs, somewhat similar to those of Dorygnathus (Fig. 60e), while Anurognathus (Fig. 60i) had rounded jaws studded with peg-like teeth. Like Peteinosaurus, it must have caught insects on the wing. (The dentition and food of the pterodactyloids is discussed in Sect. 6.6.)

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