5 Foremorly Feroucious Fuckups

1) Enteledont.

Sometimes referred to as "Devil Pigs," Entelodont was the first ascendant of the pig family, found in North America, Europe, and Asia, this bad boy went extinct about 20.9 million years ago. Entelodont could easily reach over 900 pounds and get over 7 feet tall at the shoulder! Apart from being massive and scary looking, they were omnivores which meant they eat meat and plants. Enteledont would travel in packs, so if you fought one Enteledont, you fought the herd... But why is it number one? Entelodont would often have to fight over its food with other predators so as a matter of security it would take a giant steamy shit on its meal just in case an unwanted visitor came over for dinner. YUCK!!!

Now-a-days:
 Now the living descendant of Enteledon is the mere pig... instead of traveling in packs, fending off predators, and looking badass, they have been reduced to this...I think they still shit where they eat though.

But why did it happen!?
They all died off because they were not getting enough food for the herd, less fighters in the herd equals less power for stealing a kill, no food means more die, and so on and so forth. 

2) Andrewsarchus(Andrew)

 Andrewsarchus Mongolianis is the kind of thing kids have nightmares about. Being twice as big as a Grizzly bear, Andrew was the definition of "Killing Machine" back in the day, it was almost 15 feet long, and about 4 feet of that was just teeth! It also had a very sophisticated brain for its time. It was the biggest mammalian terrestrial carnivore in the history of earth!

 Now-a-days:

 That "killing Machine" that was what you had nightmares about, is now something people count on to FALL ASLEEP! That's right, its closest living relative is anything from a sheep to a goat...
But why did it happen!?
There's no way to jazz it up, the ice age wiped them out, now we live with the warm and cuddly versions of them!

3) Megatherium

Megatherium was the size of an African Elephant and, while a herbivore, still was able to fend off attacks from almost anything in the ancient world, including an entire pack of those sabre-toothed tigers. It had eight-inch claws on its foot for the dual purposes of defense and, we can only assume, bloody murder.
It often stood on its hind legs, rendering it twice as tall as the African Bull elephant. The folks at Wikipedia describe its skeleton as "Robust." We here at Cracked prefer the phrase "holy shit gigantic." Recent research suggests that Megatherium may have used its powerful claws to actually fight Smilodon for their kills when simple trees were not enough to sustain its monstrous appetite and apparent occasional craving for mammalian flesh.

Now-a-days:

Now it is just a sloth... They are about as threatening as France. Evolution has not been kind to these creatures, you know you have reached an all time low when you are world renowned for being slow. They even have a deadly sin named after them, really, they suck so much even god hates them!

But why did it happen!?

Uhhhhhhh, we take the blaim for this one, as soon as homo sapians appeared, we sluaghtered them all.

4) Hyaenodon gigas

This horse sized mamal weighed a quarter ton and had jaws longer and more powerful than the modern aligator! They had a very good sense of smell and traveled in packs, and while in these packs they could take down literally anything in their time.

 Now-a-days:

From ferocious predator to cute and cuddly racoons. Now instead of chasing down an animal larger than itself and traveling in packs, these little guys hunt for that last bit of dust at the bottom of a cheetos bag.

But why did it happen!? 

They were overtaken by bigger animals with more muscles and more teeth, the little ones and smart ones ran and hid, and they evolved into cute little guys with poeple-hands. How cute!

5) Gastornis 

This fucking enormous bird which stood up to 7 feet tall went extinct around 45 million years ago. Its motto was take no prisoners, this thing ate everything, even us! Its beak could break bones like they were pretzels.

Now-a-days:

The once menacing bird has evolved into what is now known as the Rhea, want to know what they are known for most? Constantly running into walls! Moreover, these poor little guys are on the endangered list because of people building in their environment.

But why did it happen!? 

Pretty much what happened was they just could not breed fast enough or often enough to keep up with other animals, and on top of that the ice age wiped this feathered creature out while other warmer furrier mammals lasted.