April, 1904..] 



KNOWLEDGE & SCIENTIFIC NEWS. 



fir 



The Ancestry of the 

 CaLrnivoraL. 



By K. LvnrKKKK. 



CoMTAKi;!! with the more advanced types of ungulate, or 

 hoofed, mammals, such as the horse, the camel, and the 

 true ruminants, all the Camivora are in many respects 

 much less specialised animals, more especially as regards 

 the structure of their limbs. By this I mean that 

 although all of them are thoroughly adapted to their own 

 special mode of life, while in many instances they are 

 some of the most active, most highly organised, and 

 most intelligent of all animals, yet they depart much less 

 widely from the primitive type of mammals in general 

 than is the case with the more specialised ungulates, or 

 indeed, than ungulates collectively. In none of them 

 for instance, docs the number of toes on each foot ever 

 fall below four, while in some cases the typical five digits 

 are retained in at least one pair of feet. Then again, 

 although in the members of the cat tribe specialisation is 

 displayed by the development of sheaths for tlie protec- 

 tion of the sharp and sickle like claws, the terminal joints 

 of the toes are always of the primitixe claw-like type 

 the unguiculate form, as it is termed by naturalists, and 

 never make any approacli to either nails or hoofs. More- 

 over, all the Carni\ora are characterised by the absence 

 of that tendency to a reduction of the number of the 

 bones in the limbs by the fusion of two together and the 

 disappearance of others, which, as we ha\e seen, form 

 sucli striking features in the evolution of the more 

 specialised t)pes of hoofed animals. .Such consolidations 

 and reductions in the bony framework are indeed striitly 

 correlated with and necessary to the develipment of a 

 small number of hoofs on each foot, and are, therefore, 

 from the very nature of the case, conspicuous by their 

 absence in the Carnivora. Indeed, if we except the 

 frequent disappearance of the collar-bones, or clavicles, 

 the skeleton shows none of that anialf;atnation or loss 

 of some of its elenients, coupled with the e.\cessi\e 

 development of others, which are such noticeable features 

 in the more specialised ungulates. 



Then, again, the teeth of the Carnivora, though ad- 

 mirably adapted to the special needs of their owners, are 

 much less widely removed in structure from the primitive, 

 or generalised, mammalian than are those of the higher 

 hoofed mammals. The cheek-teeth, for instance, never 

 display that heightening or broadening of the crown, 

 coupled with those deep infoldings of the grinding surface, 

 seen in the molars of the horse and the ox. Moreover, 

 unlike what so frequently takes place in the ungulates, 

 the front teeth are always well developed, and rarely fall 

 below the typical mammalian number of three pairs of 

 incisors and one of canines, or tusks, in each jaw. In- 

 deed, when a reduction in the number of the teeth does 

 take place, as in the cats, whose short jaws do not leave 

 room for the full complement, such reduction takes place 

 at the hind end of the series. 



Among living Carnivora the group which is in the 

 whole the most generalised and the least widely removed 

 from the primitive ancestral type is that of the dogs — 

 including under this name not only the animals properly 

 so called, but likewise wolves, jackals, foxes, etc. To 

 enter into a consideration of the structure of the skeleton 

 would obviously be an impossibiliiy on this occasion, and 

 it must accordingly suffice to mention that while thetypical 

 number of five toes are retained in the fore-foot of nearly 

 all members of the group, in the hind foot there are only 



four ; and that although collar-bones arc developed, yet 

 they are reduced to mere rudiments. One other impor- 

 tant circumstance in coniU'Vj^u-^wilii i'kirJi^rt'-^^ iiiusl, 

 however, be noticed. If tno ikjVu"^ (TT Uu; wnsfTor car- 

 pus, of a dog be compared wYl'l^'^Wifr? ^ mau or of 



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elements. This is due to tTie fusion of iwi of the bones, 

 the scaphoid and lunar ; dKP tAiki)iHid£)^clI^Jhtliteristic 

 of all modern Carnivora, in which the coni])nund bone is 

 known as the scapho-lunar. 



One other feature — and this connected with the denti- 

 tion — is very characteristic of modern land Carnivora. 

 In the skull of a cat, dog, or wolf (fig. 1 ) it is well known 

 that one pair of teeth in the side of ea( ii jaw dilier 

 markedly in size and structure from all the rest, the upper 

 biting upon the lower pair with a more or less scissor- 

 like action. It is with this pair of specialised teeth that 

 a tiger or a lion cuts up the masses of flesh torn from its 

 prey into convenient lengths for swallowing ; and these 

 formidable weapons are consequently known as the car- 

 nassial, or flesh, teeth. Curiously enough, these teeth 

 do not serially correspond with one another. It will be 

 seen, for instance, both in fitfure i ;in(l fi<rure 2, that while 



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Fig. 



-5ide view o( skull of Wolfto show the carnassial teelh. 



the upper carnassial is the fourth from the tusk, the cor- 

 responding lower tooth is the fifth from the latter; liotli 

 the species in the two illustrations referred to ha\-ing the 

 full typical series of anterior cheek-teeth. Nor ir, this all, 

 for whereas the upper carnassial has no deciduous pre- 

 decessor (" baby-tooth "), the corresponding lower tooth 

 succeeds a deciduous baby- tooth. Conscrjuently, the 

 upper carnassial — to employ technical language- belongs 

 to the premolar series, while the lower carnassial is one 

 of the true molars. 



Now, when we find two organs which do not serially 

 correspond with one anotlier, modified for some particular 

 function, it may be at once taken for granted that this is 

 a highly specialised condition which did not obtain in 

 the beginning ; and this we shall find to hold good in the 

 case of the (Carnivora. 



hVom the general presence of this peculiar type of den- 

 tition, all the modern Carnivora, together with many of 

 their extinct relatives, are collectively known as theCar- 

 nassidentia. Not that it must be assumed that this 

 feature is common to them all. In the bears, for in- 

 stance, the carnassials, although still displaying traces of 

 the characteristic structure, have become comparatively 

 small and weak teeth, much smaller than the grinding 

 molars behind. And this degeneration (for by means of 

 fossil forms the feeble carnassials of the bears can be traced 



