They thought it was a nice rock for the garden. It turned out to be a dinosaur bone

Imagine you're on a walk home and you pass a construction site where you spy some very cool rocks. You think they'd look just perfect in your garden, so you ask if you can take some with you. You get the okay, and away you go.

You bring the rocks home and all seems normal until you give one of those rocks a closer look.

It turns out, it's actually a dinosaur bone.

That's exactly what happened to Mark McMenamin and his wife just a few months ago on the University of Massachusetts Amherst campus. He's a paleontologist and a professor of geology at Mount Holyoke College, so he had a pretty good idea of what he was seeing once he gave it a closer look.

Professor McMenamin joins us to talk about the finding and where it might eventually find a permanent home.

On the history of dinosaurs in the New England area:

Professor Mark McMenamin: "[Dinosaurs in the area] was indeed really a thing. And we've known since 1802 that there were dinosaurs in this area. In 1802, Pliny Moody of South Hadley discovered the first dinosaur track in our area. And it, a few years later, became quite the item locally. A lot of interest in this. The third president of Amherst College became an expert in these things. And they really represent the start of dinosaur science in America."

On finding the dinosaur bone: 

McMenamin: "It was quite an interesting day. I was out splitting wood in the backyard from a 110- year-old sugar maple tree that we had to take down because it was threatening the house. And then, with one blow of the ax, vibration seemed to have caused a rock roll off of the pile and at my feet. I looked down in the in the fading evening light and noticed a strange, porous texture that was unlike that of the other rocks. So I picked it up, took it into the house, put it in with the kitchen light and said, 'Hmm ,this really looks like fossil bone. I'm going to have to test this.'"

On what kind of dinosaur the bone could have come from:

McMenamin: "It is a very fortunate piece of fossil bone because it preserves the the outer end of the humerus bone, which is your upper arm bone. And this particular end of the humerus of this dinosaur has all the characteristics that we would expect for an early Jurassic dinosaur. The only thing that makes this one different is its size. It's huge compared to the bones of the similar part of the body known on Dilophosaurus and Cryolophosaurus."

"I think that this one was the first dinosaur, the first predatory dinosaur, to reach the 30 feet length size. And that's a first for Earth history ... [Thirty feet] would be two school buses end-to-end."

"The bone does seem to suggest that it was an animal that spent time in the water."