Everyone knows that animals come in all shapes and sizes, and millions of years ago, some of those animals were absolutely enormous.

Today, if you look across the land of North America, the biggest animal you are going to see is the bison. When you see it in person, you will likely be impressed at just how large it is, coming in at about 4 meters (13 feet) in length and weighing an average of 450-998 kg (1000-2200 lbs).

Long ago, however, an animal that utterly dwarfs the bison could be found in North America. The Alamosaurus is part of the group called titanosaurs, which are massive, long-necked sauropods.

In 1921, geologist John B Reeside, Jr came across a huge fossil near New Mexico’s Ojo Alamo Formation. That fossil belonged to an Alamosaurus (it was named after the location where it was found), and researchers estimate that it lived during the Late Cretaceous period, which was 65-70 million years ago.

It is believed that this animal, like so many others, went extinct after a massive asteroid hit the Earth, ending the dinosaurs.

So, just how big was this dinosaur? It is hard to say exactly just from fossils, but it is estimated to be around 21 meters (70 feet) long and likely weighed in at around 80 tons.

If you want a visual of just how big this is, check out this picture of a life-sized replica that was made for the State Fair of Texas:

For comparison, giraffes are around 4.3 to 5.7 meters (14-19 feet) tall and weigh up to 1930 kg (4250 pounds). Downright puny in contrast.

It is believed that this dinosaur migrated up from South America. South America is known for having a large number of fossils belonging to gigantic dinosaurs during that period.

What might have triggered the migration is not known. It could have been a changing climate, or simply animals naturally migrating to find food or avoid predators.

Whatever the case, knowing that there was once a group of almost impossibly large animals walking through North America is incredible to think about.

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