Last week, I posed a question: The Gemara in Chullin says that maulings (derusah) which are rated as causing fatal defects are only maulings inflicted with the claws, not with the teeth. This conflicts with contemporary observations of wolves, which reveal that wolves attack prey with their teeth rather than with their claws. It also seems to contradict the Gemara itself in Bava Metzia, which indicates that wolves kill with their teeth rather than with their claws.
I think that, with the aid of some comments that were submitted, I now have the solution. But first, another question: Why does the Gemara say that maulings inflicted with the teeth do not render the animal as a terefah? Surely Chazal were aware of the terrible damage that a lion can inflict with its terrible teeth and jaws!
The answer to all these questions is perhaps as follows. If an animal has been seriously mauled by a predator's teeth, it will very likely anyway suffer one of the wounds that are separately classified in the Mishnah as rendering it a terefah. If it doesn't suffer one of those injuries, then it is not classified as a terefah, because it stands a good chance of survival.
Clawing, on the other hand, renders the animal a terefah even if it does not cause any serious injury. The reason is that "venom has been injected" (a belief that developed based on bacterial infection, which can indeed be fatal). Such clawing can occasionally happen with wolves, especially since their first digit is not a blunt running claw, but a sharp claw that can be rotated and is occasionally used for gripping or ripping its prey.
So the Gemara in Chullin was aware that predators can inflict great damage with their teeth. And, as we see in Bava Metzia, Chazal knew that wolves inflict primary damage in that way. But such damage is not relevant to the category of derusah.
How does that sound? Of course, it doesn't solve all the problems with the Gemara's criteria for derusah. But it would seem to solve the basic problem regarding teeth and the mode of attack.