1879.] Origin of the Specialized Teeth of the Carnivora. 171 
THE ORIGIN OF THE SPECIALIZED TEETH OF THE 
CARNIVORA. 
BY E D COPE. 
HE specially developed teeth of the Carnivora are the canines 
and sectorials. The former are large in many orders of Mam- 
malia, and their origin is probably to be sought among the Thero- 
-morphous reptilia as Clepsydrops and Deuterosaurus, if not in 
still lower types. The successive modifications of form which 
have resulted in the existing specialized single sectorial tooth of 
the Felide have been already pointed out.? They were shown to 
consist in the gradual obliteration of the internal and posterior 
tubercles and the enlargement of the external anterior tubercle in 
connection with an additional anterior tubercle. The modifica- 
tion in the character of the dentition taken as a whole, was shown 
to consist in the reduction in the number of teeth, including the 
sectorials, until in Fets, etc., we have almost thc entire function 
of the molar series confined to a single large sectorial in each jaw. 
Observation on the movements of the jaws of Carnivora shows 
that they produce a shearing motion of the inferior on the su- 
perior teeth. This is quite distinct from the sub-horizontal move- 
ment of Ruminants, or the vertical motion of hogs and mon- 
keys. Examination of the crowns of the sectorials shows that 
the inner side of the superior, and the external side of the in- 
ferior, are worn in the process of mastication. The attempt to 
cut the tough and stringy substances found in animal bodies, 
is best accomplished by the shearing of the outer edge of the 
lower molar on the inner edge of the external tubercles of the 
superior molar in an animal with simple tubercular teeth. The 
width of the mandible is too great to allow the inferior teeth to 
shear on the inner edge of the inner tubercles of the superior 
Series. The cusps of both superior and inferior teeth engaged in 
this process, have developed in elevation, at the expense of those 
_ not engaged in it, viz: the internal cusps of the same teeth. The 
_ atrophy of the latter cannot have been due to friction, since the in- 
ternal cusps of the inferior series which have not been subjected to 
it, are reduced like those of the superior sectorial, which have. In- 
deed, it is possible that some of the Creodonta, the carnivores of 
1 American Naturalist 1878 p. 829. 
* Cope, Proceedings Academy Philada., 1865, p. 22. 
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