Just start to dig all around Coldfeet then after a little while you'll find it.It's name is Oonga Oonga.But you have to talk to Richmond first then he'll say that it's name is Oonga Oonga.Then he'll say he sent an Oonga Oonga mask to the mask salon.While your at the mask salon go to the shopkeeper then go today's special.It's snowberries they're 10,000 g,buy them.Go back to Coldfeet and start to dig again till you find Oonga Oonga[I forgot to mention the first time you see him he runs away.]this time he doesn't run away because you have snowberries,his favorite food.He takes them then runs away then go talk to Richmond again.Then whenever you want to get some fossils at Coldfeet you'll find Oonga Oonga underground with the fossils he'll give one fossil each time you see him!But you can only find him one time each time you go to Coldfeet!
Hope this helped a lot!
Hope this helped a lot!