No, it's not a new Pokémon, in fact, it's an Ancient form of the "Donphan," which was first introduced in the 2nd Gen of Pokémon "Gold, Silver & Crystal (Game)."
Great Tusk Is One Of The Paradox Pokémon In Scarlet/Violet. "Now First Thing To Know Is You Can Only Catch This Pokemon In Scarlet Version, As This Is An Exclusive Pokemon" Let's See How You Can Catch One For Yourself
Yes you can, you just have to defeat him first in the in Story and then we have two ways to catch this beast
After defeating it for the first time and getting that Titan Badge from Arven, You need to go to the "Desert in the Cascrrafa City."
Spend some time in the Desert, and you will find Great Tusk roaming around, but be careful not to knock him out, as this will be your only chance to find him here at this location.
For this method, you need to finish the game, head to "Area Zero" via the "Zero Gate," go inside and then go to "Research Station N. 4" through the Portal.
Here you can find the Great Tusk roaming around in the Dirt Portion of the cave; now, catch as many as you want.