New analysis of the scales of African coelacanths—one of two known species—reveals their life span had been erroneously estimated at only 20 years.

Not only that, female coelacanths likely carry their young for five years, three years longer than thought—and don’t reach adulthood for 55 years, says study leader Kelig Mahe of IFREMER, France’s ocean research institute. (Read how the coelacanth evolved slowly over time.)

The coelacanth’s presumed short life span had never matched with its low reproductive rates, slow metabolism, and low oxygen absorption—all qualities of slow-maturing marine animals, such as deep-sea sharks. 

“It’s been an enigma this whole time,” says Selena Heppell, head of the Department of