Four-year-old Lily Wilder was walking on the beach with her dad when she spotted a well preserved dinosaur footprint.
The 220 million-year-old footprint had been preserved in mud.
Speaking to BBC News, Lily’s dad Richard said they had been looking for shells on Bendricks Bay, Barry, in the Vale of Glamorgan.
The family couldn’t believe it was real – and said even experts thought it was “wind-up” at first.
Read more: Girl, four, discovers dinosaur footprint on beach