User blog comment:Kogath/Monster Hunter: World Discussion/@comment-26421638-20191031102905/@comment-31029678-20191102110919

I'd say Scarred Garuga should be Gen5 monster, simply because it got officially recognized only in Iceborne, still we should add notes that it "unofficially" appeared in previous games as well.

Same thing of Gajau... it first appeared in Gen3 under the name catfish and member of the fish. But Gajau is Gen5 monster as it got its own classification and new name during that Gen.