PTERODACTYLES (Gr. for wing-fingers), an extinct order of flying reptiles, variously known as Pterosauria (Gr. for wing-lizards) or Ornithosauria (Gr. for bird-lizards), whose remains occur in all Mesozoic formations from the Lower Lias to the Upper Cretaceous inclusive. Their bones are of very light, though strong construction, and hollow like those of flying birds, with well-fitting articulations, quite different from those of ordinary reptiles. The head is large and remarkably bird-like in shape, while it is fixed on the neck at the same angle as in birds. The brain is small, but resembles that of birds in its general conformation. The trunk is relatively small, with few slender ribs and a keeled breastbone (sternum). The forelimbs are always a pair of wings, the fifth digit or “little” finger being enormously elongated for the support of a smooth flying membrane (seen in specimens from the lithographic stone of Bavaria). The wings are thus constructed on the same plan as those of a bat, but instead of four fingers, only one is elongated to bear the membrane. The hind-limbs are comparatively feeble, and must have been of very little use for walking.
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Rhamphorhynchus phyllurus: restoration by O. C. Marsh, showing extent of flying membranes.—Upper Jurassic (Lithographic stone); Bavaria. |
The remains of pterodactyles are found chiefly in marine deposits, so that these reptiles must have frequented the coastlines. They probably fed partly on fish, partly on insects; but no traces of food have hitherto been observed within the fossil skeletons. The oldest satisfactorily known member of the group is Dimorphodon from the Lower Lias of Dorsetshire. The typical species has a skull about 20 centim. in length, with large teeth in front, smaller teeth behind; its tail is much elongated and slender. Equally fine skeletons of Campylognathus have been found in the Upper Lias of Württemberg. Other long-tailed pterodactyles occur well preserved in the Upper Jurassic (lithographic stone) of Bavaria and Württemberg, which is so fine-grained as to show impressions of the wing-membrane. In Rhamphorhynchus there is also a rhomboidal expansion of membrane at the end of the tail. The short-tailed Pterodactylus itself, sometimes no larger than a sparrow, is also found in the same formation. It was originally described by Collini in 1784 as an unknown sea-animal, and its “true nature was first determined by Cuvier in 1809, when he named it “Pterodactyle.” The Pterosaurians of the Cretaceous period, just before their extinction both in Europe and in North America, were of enormous size, and some became toothless. A pair of wings of the toothless Pteranodon from the Chalk of Kansas, now in the British Museum, measures about five and a half metres in span. Fragments of equally large pterodactyles with teeth are found in the English Chalk.
See H. G. Seeley, The Ornithosauria (Cambridge, 1870) and Dragons of the Air (London, 1901); S. W. Williston, paper in Kansas University Quarterly (1897), vi. 35; G. F. Eaton, papers in Amer. Journ. Science (1903-1904), 4th series, vols. xvi., xvii.