On Aristosuchus pusillus (Owen), being Further Notes on the Fossils described by Sir R. Owen as Poikilopleuron pusillus , Owen

Abstract

The Palæontographical Society in 1876 published a memoir upon a Wealden fossil, which Sir Richard Owen described as <i>Poikilopleuron pusillus</i>. These bones were then in the collection of the Rev. W. Darwin Fox, and, with the exception of the figured dorsal and caudal vertebræ, subsequently passed into the British Museum, with the Fox Collection. By the kindness of Dr. Henry Woodward, F.R.S., Keeper of the Geological Department, I have been able to examine these remains, and I would express my indebtedness for the facilities given me in making the study of which the results follow. A question necessarily arises as to the grounds on which the animal is referred to the genus <i>Poikilopleuron</i> (recte <i>Pœeilpleurum</i>), because these are stated to be “the shape and texture of the vertebræ, and especially the latter.’ This statement implies that when a dorsal vertebra was divided vertically and longitudinally, it was found to have a medullary cavity, comparable to that seen in the vertebræ of <i>Poikilopleuron</i>. In the caudal vertebra the cavity is larger. Dr. Leidy, who has recorded a vertebra of the <i>Poikilopleuron</i>-type in the Cretaceous rocks of Colorado, remarks that an internal cavity of like character was only known to him in the caudal vertebræ of the Ox ; but it is probably not rare among Dinosaurian reptiles. Mr. Hulke has shown that the character is also found in <i>Megalosaurus</i>, and other genera with hollow vertebæ have been described by Profs. Marsh and Cope. Whatever the value of this character may be,