Biologists now report being able to recreate viruses from only a complete sequence of the virus's DNA and a handful of proteins. This is worrisome and awesome at the same time. It's worrisome because some nutcase could recreate dread diseases of the past that are mostly extinct now (such as smallpox), but I'm going to explain the awesome part.
The awesome part is that we could also recreate plants and animals. Now, while we have the chance, we should sequence the genes of every endangered animal we can, and what's left of some extinct ones. (There are taxidermied examples of some extinct animals that may have usable DNA.) We should store these for later, with redundant copies.
Later, when we have the funding and environment, we would dig up the records, resequence them, and recreate the animals, gestating in a similar animal, injected in a similar egg, or having an artificial seed to plant.
Any sequenced animal would never truly go extinct, so long as we kept the records safe....