http://www.sciencemag.org/news/2021/06/living-fossil-could-reach-100-years-old

Few animals live as long as humans do. The West Indian Ocean coelacanth (Latimeria chalumnae), an endangered species of fish that can grow to 2 meters long and weigh about 100 kilograms, might be a rare exception. A new study finds the underwater giant may live to be 100 years old.

To arrive at that figure, researchers counted tiny, ringlike calcium structures on the scales of coelacanths preserved in a French museum. They discovered that, like tree rings, a new calcium ring forms every year. By counting the rings, the team found the oldest specimen was 84 years old. But the researchers believe some individuals could live as long as 100 years.