Mary the turtle is going through some life changes.

It turns out that the tortoise, who has lived in a Cleveland zoo for 55 years, has been mistakenly classified as female all that time. He will now be known as Terry, said Cleveland Metroparks Zoo spokesman Tom O'Konowitz.

"This is definitely a first for us," he told the Ohio paper The Chronicle-Telegram. The discovery was made after a routine physical exam. The sexual organs of a turtle are typically not visible during the exams, but Terry's case, his organs "became visible to the staff," O'Konowitz said.

Terry was assumed to be female because of his smaller body size and shape.

"It came as something of a surprise to finally figure out Mary's true identity," O'Konowitz said. "It took us 55 years to finally say she's a boy." The tortoise is probably between 75 and 100 years old, and was acquired by the zoo in 1955.