Set up like a traditional funeral, with a grave, a coffin, eulogies and large photos of the animal in various stages of its life cycle. The speakers could be biologists who give mini-lectures about the animal and its evolutionary history and climate experts who can explain why they died out. The gravestones could be giant stone sculptures of the animal, with the lifespan of its species’ existence written in place of the “Born - Died” years, maybe with lots of other info carved into it for posterity, like its home regions, mating and familial behaviours, etc. Maybe local politicians could [be shamed to] attend. Maybe even celebrities who could come and sing or whatever.