Heather Salt, an amateur fossil hunter from Solihull near Birmingham, said she travelled down to Lyme Regis in hopes of finding something for her own collection.
“I really just wanted to find a little ammonite,” she said.
“It was by where there’s an old dump eroding onto the beach, and there’s lots of bits of metal, so I looked down and thought it was nails stuck into something.”
But when she picked it up and realised it was stone, she started to become suspicious.
“I went and showed it to Casey [the guide] and he got so excited and he just said – ‘are you kidding me!’ and he was calling everyone over to have a look.”
“After, I said to Casey: ‘Well, I just wanted to find a little ammonite.”
“He said: ‘I would trade you my entire collection of ammonites for that.'”
Before leaving, she was found by the museum’s geology curator, Dr Paul Davis.
“He came rushing over and he got so excited and he said, ‘that’s croc!'”
She said after she learned how important the find was, she was happy to donate it to the museum.
“I did find my own little ammonite in the end which was what I really wanted.”