The ribs have capitula and tubercula, and sternal and abdominal ribs occur. The sternum has a well-developed keel, and the scapula and coracoid are large and bird-like. There are no clavicles or interclavicle.
The anterior limbs are modified to form wings by the great elongation of the fifth digit, to which a membrane was attached. The second, third and fourth digits are clawed and are not elongated in the way that they are in bats. The pollex, if present at all, is quite vestigial.
The pelvis is weak and small, and though the ilia are produced both in front of and behind the acetabula, in other features the pelvis is not bird-like. The ischia are short and wide, and the pubes are represented only by the pre-pubes. The posterior limbs are small and the fibula is much reduced. The pes is quite reptilian in type, and has five separate slender metatarsals. The two best known genera are _Pterodactylus_, in which the tail is short, and _Rhamphorhynchus_, in which it is long. The Pterosauria are found throughout the Jurassic and Cretaceous formations in both Europe and North America.
[65] According to Baur a distinct epi-otic is not recognisable in the reptilian skull.
[66] H. Gadow, _Phil. Trans._, vol. 179, 1888.
[67] See G. Baur, _J. Morph._, vol. I., 1887. R. Lydekker, _Catalogue of the Fossil Reptilia and Amphibia in the British Museum_, Parts I. & II. C.K. Hoffmann, _Reptilien_, in Bronn's _Classen und Ordnungen des Thierreichs_, Bd. VI., 3 abth. 1879-90.
[68] T.H. Huxley, _Quart. J. Geol. Soc._, vol. XV. p. 649, 1859. R. Owen, _Catalogue of Fossil Reptiles of S. Africa in the British Museum_, London, 1876. H.G. Seeley, various papers published in the _P.R. Soc. London_, and _Phil. Trans._
[70] An ent-epicondylar foramen is one piercing the humerus on its inner side just above the condyle.
[71] According to Hulke they should be regarded as the omosternum,--the clavicles and interclavicle being wanting.
[73] R. Lydekker, _Nat. Sci._ vol. I. p. 514, 1892. Further references are there given.
[74] The exact position of the suture between the prefrontal and postfrontal is not known.
[75] A. Günther, On the Anatomy of Hatteria, _Phil. Trans_, vol. 157, 1867, p. 595.
[76] =Zygosphenes= are extra articulating surfaces borne upon the anterior face of the neural arch; they fit into corresponding structures, the =zygantra=, which are borne on the posterior surface of the neural arch of the preceding vertebra. Ordinary zygapophyses always accompany them.