New Jersey and ancient creatures sort of go hand in hand.

Haddonfield, New Jersey has a dinosaur named after it.

I thought that the hadrosaurus was the first complete dinosaur skeleton found in the world; while doing research on prehistoric animals that lived in New Jersey I learned that this was not true.

The Hadrosaurus was the first almost complete dinosaur skeleton found. It was the most complete for its time, but not fully complete.

Still, to have a dinosaur named after a New Jersey town is pretty cool.

After the dinosaurs went extinct, the large mammals took over.

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Honestly, large is an understatement. Mammals were enormous, gigantic, gargantuan...

Though, it is crazy to think that the blue whale is the largest mammal to have ever lived and still lives today.

NJ Parks posted a handy little map to show all of the different creatures that roamed New Jersey at one point as a way to highlight how great New Jersey is for fossil hunting.

New Jersey Prehistoric Animals Map

Seeing that we had mastodons, wooly mammoths, and plesiosaurs in New Jersey was pretty cool, but one animal in particular caught my eye.


I don't know why this surprised me considering the modern-day sloth is native to South and Central America, it would make sense that sloths could have lived in North America at some point in history.

NPS illustration by Benji Paysnoe

How big was the giant ground sloth?

The giant ground sloth or megalonyx could get up to 9.8 feet in length and could weigh up to over 2,200 pounds!

To put this into perspective, an American Bison can weigh over 2,000 pounds and a male bison can be 11 feet in length.

Can you imagine a sloth the size of a bison?

When did the giant ground sloth live?

These ginormous creatures lived during the Pleistocene epoch which lasted from 2.58 million years ago to 11,7000 years ago. If you ask me, it seems like they could've broken up that time period a bit more because it covers a crazy amount of time.

This time period also includes the last glacial period.

What did the giant ground sloth eat?

Luckily for all of the other prehistoric creatures running around New Jersey at this time, like its more modern relative, the giant ground sloth was an herbivore.

Fun facts about the giant ground sloth

Sid the Sloth from Ice Age was modeled after the giant ground sloth.

The actual species Megalonyx jeffersonii was named after Thomas Jefferson. The then Vice President Thomas Jefferson received a few fossilized megalonyx bones as a gift from Colonel John Stuart.

When Jefferson described the bones in a paper, he compared them to lion bones and assumed they belonged to a carnivorous big cat.

James Akin after a chalk drawing by W.S. Jacobs. Transactions of the American Philosophical Society, Vol. 4 (1799).
Library of Congress

Later, zoologist Baron Georges Cuvier described a different species of giant sloth found in Argentina, which led to Jefferson amending his previous description and comparing it to the giant sloth.

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