My take on it: First (and this is all based on whether they were actually found. Based on the Noah's Ark reference in the same post, I'm skeptical) , it would not be the first time we have found animals thought to be extinct. I fail to see how it means anything that we thought an organism was extinct, but they turned out to still be around. Secondly, why would they remain unchanged? Probably beacuse their environment, the inside of a volcano, can be a relatively unchanging environment. Some volcanos go dormant. But if a volcano remains active, it will be pretty much the same environment after 1,000 years, 1,000,000 years or even 1,000,000,000 years.