But, leaving aside Nyctodactylus, it is very much of a question whether the differences between Pterodactylus and Pteranodon are sufficient to locate them in different families, let alone different suborders.
The two genera have the following in common: Tail short. Skull with more or less elongated, pointed jaws, and very small upper and lower temporal fossae. Narial opening large, confluent with the pre-orbital foramen. Cervical vertebrae elongated, with rudimentary spinous processes. Fore and hind extremities, quite alike.
Pteranodon differs from Pterodactylus, so far as that genus is known, in the united coracoscapulae and pubes, both of which characters are found in Rhamphorhynchus.
The sole family characters remaining then, for Pteranodon, are, absence of teeth, a supra-occipital crest, and the articulation of the upper end of the scapula. Now it seems evident that to place the pteranodonts in a group equivalent to all the other pterosaurs is unwarranted, and any classification that will not show the more pronounced relationships with Pterodactylus is faulty. I would, therefore, propose the following:
- Order Pterosauria.
- Family Pterodactylidae,
- subfamilies Pteranodontinae, Pterodactylinae.
- Family Rhamphorhynchidae.
- Family Ornithocheiridae.
As regards the geographical distribution of the Pteranodonts, they have hitherto been recognized only from Kansas, but I am firmly of the opinion that they occur in Europe, and, if so, it is very probable that the name Pteranodon must be eventually given up. In fact, a toothless form of Pterodactyl was described by Seeley as long ago as 1871, under the name of Ornithostoma. I cannot refer to his description at present, and can, therefore, give no opinion as to their identity. It seems certain that the peculiar form of the scapulae and their vertebral articulation[3] occur among some of the European forms, which would strengthen the belief that Pteranodon is also an European genus.
In view of the above, the practice of the American text-books in Geology in introducing generic names of characteristic fossils as names of the geological horizons whence they come, is very reprehensible, in my opinion. Even the late edition of Leconte’s Elements contains a long list of such names, the greater portion of which have been relegated to the limbo of synonymy by paleontologists. It is greatly to be desired that the name “Pteranodon Beds” shall not become established, so long as there is the least doubt of the validity of the name itself.