86 DR. R. BROOM ON THE SKULLS OF DICYNODONTS. [June 3, 



2. Remarks on certain Differences in the Sknlls o£ ,Dicjno- 

 donts, apparently due to Sex. By R. Broom, M.D., 

 B.Sc, C.M.Z.S. 



[Received April 11, 1902.] 

 (Text-figure 16.) 



In classifying the Dicynodont skulls from the Karroo deposits 

 of S. Africa, one is at once met by the difficulty that scarcely two 

 of them seem to agree in all respects. Even in a series of skulls 

 from one stratum and one locality, and where the presumption is that 

 a number at least must belong to the same species, the differences 

 are such that one might readily incline to make each skull the 

 type of a distinct species. Owen, in his ' Catalogue of S. African 

 Reptiles,' describes 36 specimens of Dicpiodont skulls, and these, 

 he believes, represent 32 difierent species. Lydekker, in his 

 British Museum Catalogue, x-ecognizes among Owen's specimens 

 only 18 good species and 4 which are doubtful. 



Though the difficulty in classifying Dicynodont skulls is to some 

 extent due to the different ways in which specimens are crushed 

 and to the impei'fection of the specimens, it is mainly owing to 

 our ignorance of the changes which may be produced by age and 

 to the differences due to sex. Small Dicynodont skulls are found 

 not more than 3 inches in length with weU- developed tusks and 

 well-ossified bones, which m their genei-al characters resemble 

 some of the largest skulls that have been discovered. Until a 

 miTch greater number of specimens has been found, it will be 

 impossible to decide definitely whether many of the small skulls 

 are those of small species or of the young of the larger kinds. 

 "With regard to the diflerences due to sex, I have come across a 

 few sku.lls which seem to give us some help. 



In Port Elizabeth there is a Dicynodont skull in the collection 

 of the Eastern Province Naturalists' Society, which differs very 

 markedly from any previously described; and this I have de- 

 scribed ^ as the type of a new species, D. latifrons. In the Gill 

 CoUege, Somerset East, is a large skull which I believe belongs to 

 the same species, but which differs very strikingly from the Port 

 Elizabeth specimen in the structure of the maxillaries and tusks. 

 Both the skulls are from Burghersdorp, and agree in the follow- 

 ing features -.^The nasal region is very greatly developed and has 

 a prominent median ridge ; the frontal i^egion is flat and exceed- 

 ingly broad, causing the orbits to look directly outwards ; the 

 parietal crest rises sharply up from the frontal plane, making an 

 angle of about 120° with it. In the Port Elizabeth specimen the 

 tusk is feeble and is directed forwards almost in a line with the 

 malar arch. Along the lower margin of the maxillary there 

 passes backwards from near the root of the tusk a well-marked 



1 R. Broom, " Ou two new Species of Dicynodouts," Ann. S. Afr. Mus. vol. i. 

 pt. 3, 1899, p. 452. 



