Prehistoric animals as fantasy monsters

[Yora]

Every boy above the age of 8 knows about dinosaurs which may partly be the cause they often don't seem to fit in with fantasy wildlife. But there's also a lot of almost unknown prehistoric mamals and other ancient reptilians which would be really cool monsters but unknown enough to stick out as out of place.

Now I pretty much don't know anything about these animals except for cave bears, which are just really big bears, and sabre toothed lions, which are big lions with huge teeth. (And how come those get dinosaur-crazy kids cheering as the only mammal?)
So, and suggestions for cool prehistoric animals that make good fantasy monsters?

[erikun]

Megatherium ("Megasloth") was a 20' tall and weighed 4 tons, and as a big shambling herbivore the size of an elephant, probably had no problem fighting off or killing predators.

Microraptor was a small winged dinosaur perhaps best noted for having four wings (one on each limb) with clawed fingers.

Andrewsarchus is most noteworthy for its size and jaws, thought to be strong enough to bite through turtle shells and bone. It is also thought to be hooved, with its closest relative being sheep - think about that one for awhile.

Phorusrhacidae, or "Terror Birds", were large flightless birds larger than an ostrich, which hunted down and ate meat like a raptor.

[awa]

terror birds
short faced bear
ground sloth http://en.wikipedia.org/wiki/Megatherium

[TheThan]

The BBC series “Walking with prehistoric beasts” is a good place to get inspiration for what you’re talking about. Here’s a good place to look into the subject: http://en.wikipedia.org/wiki/Pleistocene_megafauna

Another good place to start is with Dire animals. You can easily use them as relics of another time, older, meaner cousins of more modern animals. You can also use both the dire animals and the prehistoric ones as exotic versions of regular animals. you can also use some classic mythological creatures, such as the Roc, hydras etc as rare but powerful creatures.

I have always felt that it’s a bit awkward to throw in such animals. That’s mostly because of the strong medieval flair of a lot of RPGs. Using prehistoric animals is not as difficult as magical beasts (many of which are sentient but probably shouldn’t be), but they do posses the challenge of fitting them into an ecology that makes a certain amount of sense.

I’ve always wanted to run a “caveman” game. Where the players are all part of a tribe of humans trying to survive during the ice age, they have to compete with other tribes, hunt and gather food, deal with dangers such as the environment and other predators.

[Eldan]

I always wanted to include Placodermi in an aquatic game. I mean, just look at Dunkleostus.

[Yora]

You need something to compare them with.

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Though this one looks more like 6m rather than the maximum size of 11m.

Edit: This is more like it.

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[Thane of Fife]

Another good place to start is with Dire animals. You can easily use them as relics of another time, older, meaner cousins of more modern animals. You can also use both the dire animals and the prehistoric ones as exotic versions of regular animals. you can also use some classic mythological creatures, such as the Roc, hydras etc as rare but powerful creatures.

In fact, dire wolves are prehistoric animals. See the wikipedia entry. Pre-3e, cave bears, megalodons, and smilodons (sabre-toothed tigers) were all in the Monster Manual. In 3e, though, they were all simply given the "Dire" title, as if somebody didn't know that dire wolves were actually a real animal.

What I'm trying to say is, this is probably very much the right way to aim.

[awa]

dire wolves may share the name of a real world animal but real world dire wolves were big shure but still well under 200 pounds nowhere near the 800 pound dnd monster.

the dire shark is half the size of the maglodon (by length)

the dire bear is more carniverous and about 8 times heavier then a cave bear
a dire tigre is 6 times bigger then a smilodon (by weight)
(also dire animals have spikes on them)

[Serpentine]

Australia has some awesome megafauna. A short list of examples:

Sheep-sized echidnas
Hippo-sized wombats
Marsupial tapir
Kangaroos probably taller than you
The demon duck of doom
A monitor lizard that would come up to your hip on all fours.
A large crocodile... that would chase you across the plains
An enormous turtle which would also chase you across the plains (except it's a turtle)
Extra-large Tasmanian devils (which are already pretty fricken scary)
And then there's the marsupial lion and Tasmanian tiger...

Also, my personal favourite real-world dragon: Quetzalcoatlus.