Given only a tiny fraction of all the species that have lived on Earth are still alive today, there have been a great many amazing creatures lost to the mists of time.

Anyone else have an interest in prehistoric animals, and which ones do you find most fascinating?

The Ground Sloth is the greatest creature

Carnotaurus

Entelodont 

Marsupial "Lion"

Some of my top picks:

Titanoboa, the biggest known snake to ever live

Giant Moa, which survived as recently as the 1500s

Thylacine/Tasmanian Tiger, survived until the 20th century

Woolly Rhinoceros, a resident of the more recent Ice Ages

Basilosaurus, a predatory whale 15-18 meters long

The first one: Glyptodon. It was basically a big armadillo, but the size of a tiny car. The cool thing is that it actually coexisted with humans, as it went extinct 4000 years ago. There's also fossil remains that show damage from man made spears.



Second one: Terror bird. This thing hunted horses. It went extinct around 2 million years ago. It couldn't compete with the sabred cats that migrated to its continent when north and south America joined.



Third: Elasmotherium. Look at that ridiculous giant horn. 



Extra: Paraceratherium. The largest land mammal that ever lived. This animal towered over elephants. It was actually part of the rhinoceros family.



There are so many cool extinct animals to talk about, like the megafauna of Australia (Andrewsarchus, Megalania). An interesting topic to talk about is why so much of the giant animals died out so fast.

Why are it's arms so small?

They should be bigger! 

With remains of that family of birds now found in Europe and Algeria, it's actually discussed that this kind of bird could have survived longer than that, as it has so many clear parallels with the Roc. On the other hand, the mainstream theory about the Roc goes more about travelers from Eurasia meeting ostriches, and not having seen flightless birds before, mistake the ostriches as the chicks of some gargantuan bird of prey.

Both those cases are not yet fully accepted as true phorusrhacid. It could be a possibility though.

Laganosuchus, or the pancake crocodile.

 

There are many weird and interesting extinct crocodilians. This is just an example of one croc with an interesting adaptation.