Females don't hit sexual maturity until their late 50s, the study said, while male coelacanths are sexually mature at 40 to 69 years.

But by applying a standard technique for dating commercial fish, French scientists calculated they actually live close to a century, according to a study in Thursday's Current Biology.

But the French scientists found they were missing smaller lines that could only be seen using polarized light — the technique used to figure out the age of commercial fish.

Using the technique, the scientists figured pregnancy lasts at least five years in coelacanths, which have live births, Ernande said.