2 



SIR R. OWEN ON THE. AFFINITIES OF THYLACOLEO CARNIFEX. 



The species of carnivorous Phalanger is not named. No evidence of such by fossil 

 specimens has reached me, nor have I found such exceptional habit of an existing 

 species of Phalangista elsewhere noted. 



As the palgeontogical survivors of Dr. Falconer and Mr. Krefft have not signified 

 any opinion of the fossil evidences, more or less fragmentary, of Thylacoleo discovered 

 subsequently to the papers above cited, I deem it due to them to make known the 

 most complete and instructive example of the mandibular and dental structures of the 

 mooted species which have yet reached me. 



The subject of the annexed drawings (Plate 1) is the right " ramus " of the lower 

 jaw, which was extricated in the present year (188G) from breccia of the Wellington 

 Valley cave. A careful cast of this specimen has been transmitted to me by 

 G. P. Ra^ibay, F.L.S., successor to Mr. Krepft, and present Keeper of the Australian 

 Museum of Natural History, Sydney, New South Wales, together with the three 

 di'awings of the original specimen, natural size, herewith annexed. 



The dentition of this specimen closely repeats the characters of the mandibular 

 teeth described and figured in fragmentary specimens.* The additional characters, 

 which I interpret as decisive of the carnassial nature of Thylacoleo, are those of the 

 hinder end of the lower jaw, including the articular process. This part is a "condyle" 

 transversely extended, antero-posteriorly convex, as in both Lion and Tiger. The 

 angle, a, of the ramus is bent inwards as in other Marsupials, including the smaller 

 existing pouched Carnivores. In Thylacoleo, to add to the force of the biting actions 

 of the mandible, a subsidiary ridge ending in the process, figs. 1 and 3, h, is developed 

 from the outer side of the broad angle of the jaw ; the homologue of this ridge and 

 process, wanting in placental Carnivora, is developed in the largest of the existing 

 marsupial ones, e.g., Thylacinus cynocephaliLS. The coronoid process of the mandible 

 in Thylacoleo (figs. 1-S, (/) rises high above the condyle, and broadens antero- 

 posteriorly as in the feline placental Carnivores. The entry of the dental canal is 

 shown at e, fig. 2 ; the exit at /, fig. 1. 



As the figures in Plate 1 are of the natural size, descriptive dimensions are omitted. 



What to me is of most interest in this decisively instructive fossil are the evidences 

 of carnivorous modifications superinduced upon the primitive, and at present prevailing, 

 diprotodont marsupial type. In the mandible of the vegetarian kangaroo [Macropus) 

 the incisive part of the dental series is represented, as in Thylacoleo, by a single pair 

 of large incisors ; but these, as in the allied genera Dendrolagus, Bettongia, Hypsi- 

 prymnus, are procumbent, depressed instead of compressed, having a smooth flattened 

 upper surface with lateral margins, instead of the sharp-pointeji and hinder trenchant 

 border of the corresponding tooth of Thylacoleo. 



The tooth answering to the trenchant carnassial premolar (figs. 1 and 2, p. 4) in 

 Thylacoleo has also tlie largest crown of the molar series in the aliove-cited gramini- 

 vorous Marsupials, but in them the margin of the crown is bi-okeu by notches in which 



* Hoc ' IMiil. TrajiH.,' 1871, p. 2:38, I'lato 13, fit,'. 1, and JMatc 14, 



