There are many languages that were extinct and have been studied and spread again. Most of these languages were once common in their native areas, due to marginilization of local language, low social status and poverty, the native speakers fail to pass these languages to next generation.
Some of them are: Chochenyo, Ainu, Cornish, Dalmatian, Barngarla, Kaurna, Hebrew, Latin, Wampanoag,Sanskrit, Palawa kani, Mutsun, Occitan Gascon, Leonese, Lazuri, Livonian and many more.