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 fore-limbs 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 . The remains of pterodactyles are found chiefly in marine deposits, so that these reptiles must have frequented the coast-lines . 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 .

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fine skeletons of Campylognaehus have been found in the Upper Lias of Wurttemberg . Other long-tailed pterodactyles occur well preserved in the Upper Jurassic (lithographic stone) of Bavaria and Wurttemberg, 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 deter-mined 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, 187o) and Dragons of the Air (London, 1901) ; S . W . Williston, paper in Kansas University Quarterly (1897), v1 .

35; G . F .

Eaton, papers in Amer . Journ . Science (1903-1904), 4th series, vols. xvi., xvii . (A . S .