Thylacinus cynocephalus – the last known member of this species (‘Benjamin’), a.k.a. Tasmanian tiger, died of exposure in the Hobart Zoo in 1936. There are ongoing attempts to bring it back to life by cloning its DNA; especially commendable are the efforts led by Don Colgan.
The thylacine’s retractile jaw (very impressive) and odd striped fur made it a very unique mammal… you can see its last appearances in rare film (now preserved in Youtube).
On the Aussie website ‘A day in the life sciences in Australia’, do not miss ‘Reviving the Lost Tigers’ by Peter Ridgeway and Michelle Brown. Well done work, it highlights the DNA work and progress of Dr. Colgan at the Museum; it includes some pictures of the data. Another excellent piece on the subject can be found at “Attempting to make a genomic library of an extinct animal: Australian Museum online”, although the best video (a must-see) on the Thylacine DNA & genome is possibly this one, “Return of the Tasmanian Tiger”.