On the Structure of the Skull of a Pliosaur

Abstract

In the present communication I propose to give a short account of the cranial structure of the Plesiosaurian reptile known as Pliosaurus ferox (Sauvage), a very fine skull of which has recently been acquired by the British Museum. Like so many other reptilian fossils from the Oxford Clay, this specimen was obtained in the neighbourhood of Peterborough by A. N. Leeds, Esq., F.G.S., who has expended much time, patience, and skill in fitting together the numerous fragments into which the bones were found broken. The result, however, is well worth the trouble taken, and the specimen is now perhaps the finest Pliosaur skull known. The extreme length from the occipital condyle to the anterior extremity is 112 cm., while the width at the quadrate region, perhaps somewhat exaggerated by crushing, is 50 cm. The desription of this skull is facilitated by the great similarity which exists between it and that of Peloneustes philarchus , of which an account has already appeared. This similarity is so striking that it seemed not impossible that the present specimen might be merely the skull of an old individual of Peloneustes : but there are a number of differences which tend to show that such is not the case. In the first place, the total number of teeth in the upper jaw of Peloneustes is greater, and there are six instead of five in the premaxilla; it is, however, possible that a premaxillary tooth might be lost in growth, since this actually occurs in Crocodilus porosus , so