24rt ^JI■:^[OIL•S of the QFICEySLAXD MUSEUM. 



AN ICHTHYOSAURIAN SKULL FROM 

 QUEENSLAND. 



By Heber a. Longman. F.L.S., Director. Queensland Museum. 



(Plate.? XV and XVI and Text-figures 1 and 2.") 



The remains which are the subject of this paper were found at Galah Creek, 

 about twelve miles from Hughenden, in the Rolling Downs formation (Lower 

 Cretaceous) of Western Queensland, and were collected, forwarded, and kindly 

 donated to the Queensland Museum by Mr. S. Dunn and Mr. WilHam Elliott in 

 ilay, 1914. It is my pleasant duty heartily to thank these gentlemen for their 

 enthusiastic work in securing this large and valuable specimen for our collections. 



Material. — As will be seen from the profile view, illustrated in Plate XV., 

 this large .skull is in six pieces. The extreme end of the rostrum is missing, but, 

 judging from the structure of the anterior part preserved, only a small portion 

 would be needed to complete the skull. Gilmore^ has pointed out how frequently 

 the extreme anterior segment is missing in Ichthyosaurs, and how fractures are 

 caused by the cracking of specimens when enclosed in an elongate concretionarj^ 

 mass. 



The skull is massive, with a maximum length (mandibular) of 1,026 mm., 

 and a maximum width (articular area of mandible) of 395 mm. It is evident that 

 great changes have taken place since it came to rest. As a result of tremendous 

 vertical pressure, the whole of the teeth, with the exception of broken roots, have 

 l)een forced from the continuous dental grooves, characteristic of Ichthyosaurus, 

 and the premaxillary and mandibular rami are now in juxtapo.sition. Fortunately, 

 many of the teeth have been preserved, mostly as fragments, on the lateral and 

 lower surfaces of the jaw. In the posterior part of the skull there are still greater 

 evidences of changes under intense pressure. On the left-hand side the orbit has 

 been crushed down and its original contours are not distinguishable. As a result 

 of this lateral torsion, the mandible has been somewhat displaced to the right. The 

 supratemporal fossae are preserved in fairly symmetrical condition. Great difficulty 

 has been experienced in studying some of the component parts. The distortion of the 

 skull is accompanied by a very close investiture of the remains by a fine hard lime- 

 stone matrix, which in places is almost indistinguishable from the actual fossil. 

 The matrix involving Cratochelone berneyi,^ described by the author in 1915 from 

 the same district, was very similar in texture. This investing material evidently 

 jienetrated the skull after the decay of cartilage, cementing the disrupted elements 

 together. 



^ C. W. Gilmore, Mem. Carnegie Mus., Pitts., II, 1905, p. 80. 

 2 H. A. Longman, Mem. Qld. Mvis., Ill, 1915, p. 25. 



