A family who went for a walk on the beach never expected the discovery they’d make—with the help of their dog.

Tamás, 18, who posts to Reddit under the username u/Serious_Comfortable3, took to the r/Fossils sub on March 10, where he shared a photo of what initially looked to be an enormous black tooth, as big as his hand.

He wrote: “Just found this on a Dutch beach. Looks like a teeth. Does [anybody] know what this is?”

Speaking to Newsweek, he explained he, his family and his dog were at Langevelderslag beach, about an hour outside of Amsterdam, to enjoy some good weather.

“At one point, I saw my dog running toward me with something in his mouth, and I thought it was just a stick. I even threw it away so he could play fetch with it,” he admitted.

But, when he looked closer, he realized “it really resembled a fossil—something like a tooth.

“So I decided to bring it home, and posted it on a forum.”

It had a big reaction on Reddit, racking up hundreds of upvotes and dozens of comments.

“People suggested all sorts of things: a sloth claw, a shark tooth and even a pterosaur toe,” he told Newsweek—but eventually he got an answer from a zooarchaeologist.

The expert told Tamás the discovery is likely a “fossilized inner horn, probably from a European bison that lived during the Last Glacial Maximum, between 100,000 and 25,000 years ago.”

The Last Glacial Maximum (LGM) saw eight percent of the planet’s surface covered in ice and sea levels around 410 feet lower than today.

It concluded around 19,000 years ago and then followed a warming and melting process lasting for about 8,000 years.

Tamás has also sent the photos to Naturalis Biodeversity Cennter, the largest natural history museum in the Netherlands, to confirm the find—and said if the center is interested, “it would be very awesome to have it displayed in the museum.

“Otherwise I think I will make a little stand from wood for it, and display it in my room.”

Reddit users were impressed by the find, as one user wrote: “Looks like a horn from a steppe bison. Bones from them were quite common finds from [trawlers] from Dogger Bank before the bottom dragging bans. But bones do wash up on beaches in northern Europe and the east of the UK.

“I’ve seen a lot of vertebra and leg bones. But only horns a couple of times. It’s a cool find.”

And as Tamás told Newsweek: “Huge props to my dog! Such a cool find!”

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