Does any mammal have exposed teeth at birth? It seems like a newborn having teeth would not make nursing easier.
Does any mammal never form teeth?
While I don’t know if *all *mammals are toothless at birth, although this site suggests they are, I can tell you that human babies with teeth nurse just fine. They bite occasionally, which usually makes Mama yelp, but it doesn’t hinder nutrition at all.
As for the second question, see here:
There are human babies born with teeth.
Yes, but it’s hardly a regular deviation within the species. I wouldn’t use a three-legged goat as an example of triped mammals.
Echidna has no teeth, right?
Piglets are born with canine teeth, and I think I remember some other species (some cervids, ruminants, etc.) being born with them. Or if not born with them, they erupt in the first few hours/days of life.
In the case of piglets, the teeth are usually taken out in the first couple of days because they can irritate the sow (and in production, you don’t want that).
That’s part of why I stopped nursing when the kidlets got to be about six months old…those things are sharp! Owie!
I don’t know how Mommy cats and dogs do it.
Calves (baby cows for the more urban people 
) have teeth. I’ve had them cut my finger whilst trying to teach them to suck rubber teats. :eek: Those cuts hurt!
On reflection, I would think all grazing animals would have teeth at birth, as it’s common to see calves, lambs and kids nibbling grass within a few days of birth. They won’t survive with out their mothers milk for a few months, but they need to develop their rumen.
A strong tendency to bite while nursing is probably not an adaptive advantage, so even infants with teeth rarely use them on mama.