The proximal end of the tibia (Pl. III. fig. 8) possesses the great outwardly bent cnemial crest which is characteristic of that bone in the Dinosauria.
The ilia, femora, and tibiæ in the Bristol collection are all of one kind; and the question therefore arises, do they belong to Thecodontosaurus or to Palæosaurus? Considering that three sets of Thecodontosaurian teeth have been found for only a solitary Palæosaurian tooth, the probabilities would seem to be in favour of the bones belonging to Thecodontosaurus. But, on the other hand, the teeth of Thecodontosaurus are Scelidosaurian in character; and it seems to be hardly likely that these teeth should have accompanied hind limbs which are the reverse of Scelidosaurian, and exaggerate the peculiarities of those of Megalosaurus, when we have, in Palæosaurus, a tooth so like that of Megalosaurus that it is only distinguishable by critical examination. With the present materials I do not think any decision can be safely arrived at on this question, and I shall speak of the bones as those of Thecodontosaurians, without prejudice as to the particular genus to which they may belong.
I may observe, in conclusion, that the ilium is shorter in proportion to the femur in these Dinosauria than in any others with which I am acquainted, and that the cavities in the bones are so extraordinarily large and well defined that, if found alone, it would be hard to distinguish some of them from those of Pterosauria.
The Thecodontosaurians, then, are Dinosauria; but the question may be raised whether the conglomerate in which they are found is really Triassic, some geologists appearing to be inclined to think them of Rhætic age, while Von Meyer, as has been seen, looks upon them as transitional between Muschelkalk and Keuper[1]. It does not lie within my province to discuss this problem, the decision of which, either way, will not affect the occurrence of Dinosauria in the Trias; and I therefore pass on to examine into what evidence there may be of the existence of Dinosaurian reptiles in the Warwickshire sandstones, the Triassic age of which appears to be beyond question.
Many years ago certain teeth were discovered in these sandstones by Dr. Lloyd, and were placed by him in the hands of Professor Owen, who has thus described them in his 'Odontography,' which was published between the years 1841 and 1845:—
"In their compressed form, anterior and posterior serrated edges, sharp points, and microscopic structure, these teeth agree with those of the Saurian reptiles of the Bristol conglomerate. In their breadth, as compared with their length and thickness, they are intermediate between the Thecodontosaurus and the Palæosaurus platyodon. They are also larger and more recurved, and thus more nearly approach the form characteristic of the teeth of the Megalosaurus. From these teeth, however, they differ in their greater degree of compression and in a slight contraction of the base of the crown."
- ↑ On this question I refer the reader to a forthcoming paper by my colleague Mr. Etheridge.
