Here is a selection of images of the remains of remarkable animals long extinct, from the American Museum of Natural History. This is another place that takes more than a day to peruse.
Stependemys geographicus (side necked turtle), 5 million years ago
Glyptotherium texanum, 2.5 million years ago, North America, this one probably killed by a large jaguar-sized pussycat, leaving two puncture marks on the top of the skull
Megaloceros giganteus (Irish Elk), 11 thousand years ago, regrew antlers each year.
Mammut americanum (mastadon) 11 thousand years ago. This specimen was found intact, standing upright, inside a peat bog
Mammuthus primigenius (wooly mammoth), 21,000 years ago
Brontosaurussy thing (but not called that anymore)
Not a T Rex (without Marc Bolan) but probably an Allosaurus