"The deal is as dead as a dodo."
Dodo is the other most famous and documented species that has extincted besides dynasours.
If something is said to be as dead a dodo, it is not working, obsolete, or unavailable. It refers to the flightless and now extinct bird that was taken by sailors to their ship and kept alive for fresh meat. The Portuguese named the birds doudo, meaning stupid. Dodos were caught and eaten into extinction during the 17th Century. Thereafter, the phrase passed into the English language.
Dodo got it's fame largely due to the sorry told by 'Alice in the Wonderland".