SUMNER, Iowa (KWWL) -- Four children in Sumner, Iowa were exploring a creek when they decided to build a dam out of twigs.
"We were going to build a dam to hold back all the water and we wanted to clear out the rocks so it wouldn't be all rocky so we wouldn't get cuts on our feet," said 12-year-old Brylie Volker.
All plans came to a halt when they stumbled upon something large hooked into a twig.
The friends thought it was a dinosaur tooth, and it turns out they were close.
Professors at Upper Iowa University believe that the tooth belonged to a mastodon more than 20,000 years ago.