The giant Irish Elk went extinct at the end of the Ice Age. It's believed that the huge size of their antlers as well as climate change caused their extinction.
This animation by Brown Bag Films is sweet and sad. They also did the amazing Give Up Yer Aul Sins, which I watch every Christmas. And Ding Dong Denny O’Reilly's History of Ireland which had me rocking in my seat with laughter.