On Aristosuchus pusillus (Owen), being further notes on the fossils described by Sir R. Owen as Poikilopleuron pusillus, Owen / by H.G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: On Aristosuchus pusillus (Owen), being further notes on the fossils described by Sir R. Owen as Poikilopleuron pusillus, Owen / by H.G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    [From the Quarterly Journal of the Geologtcal Society for May 1887.] On Aristosuchus pusillus (Oiuen), being Further Notes on the Fossils described by Sir R. Owen as Poikilopleuron pusillus, Owen. By H. G. Seeley, F.R.S., F.G.S., Professor of Geo- graphy in King’s College, London. [Plate XII.] The Palieontographical Society in 1876 published a memoir upon a Wealden fossil, which Sir Richard Owen described as Poikilopleuron pusillus. These bones were then in the collection of the Rev. W. Darwin Fox, and, with the exception of the figured dorsal and caudal vertebrae, 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 Poikilopleuron (recte Poecilopleurum), because these are stated to be “ the shape and texture of the vertebrae, and especially the latter.” This statement implies that when a dorsal ver- tebra was divided vertically and longitudinally, it was found to have a medullary cavity, comparable to that seen in the vertebrae of Poikilo- pleuron. In the caudal vertebra the cavity is larger. Dr. Leidy, who has recorded a vertebra of the Poikilopleuron-type in the Cretaceous rocks of Colorado, remarks that an internal cavity of like character was only known to him in the caudal vertebrae of the Ox ; but it is probably not rare among Dinosaurian reptiles. Mr. Hulke has shown that the character is also found in Megalosaurus, and other genera with hollow vertebrae have been described by Profs. Marsh and Cope. Whatever the value of this character may be, I submit that it is not generic, while there is no evidence which would associate any group of osteological characters with chambered vertebras of this type. Mr. Hulke has advanced some evidence to show that Poikilo- pleuron is Megalosaurus, and it will be admitted that the corre- spondence in form and character of the caudal vertebras, and in the distal end of the tibia in these Oolitic Dinosaurs, if insufficient to establish absolute identity, at least proves a close affinity between them. And therefore the conclusion is legitimate that the re- semblances found in the tail extend substantially to the sacrum, and that the same type of sacrum is found in Poikilopleuron as in Mega- losaurus. When examining the validity of the genus Poikilopleuron Mr. Hulke did not discuss the sacrum, which constitutes the chief part of the evidence for the species Poikilopleuron pusillus. If Sir Richard Owen is correct in his description of the sacrum of that fossil in referring only two vertebrae to the sacral region, and u the sacrum of Megalosaurus consists of five anchyloscd vertebrae,