Meet the first newly discovered mammalian species in 35 years, the olinguito, as presented by Rob Nelson from Untamed Science:
I think you mean first in the New World in 35 years. Several have been discovered recently in Viet Nam.
Yes, of course! I did not clarify that it was the first new species discovered in the New World. Thank you for catching that!
It's not the first new mammal discovered in the New World for 35 years either - not even the first in the last decade. You're thinking of the first New World Carnivoran described in 35 years. New species of opossums, bats, monkeys and sloths have all been described in the 21st century in the Americas; as have a few others whose specific status is controversial, like the Dwarf Manatee.