How long do crinoids live?

For the first time, the lifespan of deep-sea stalked crinoids was determined using the bomb radiocarbon method, which relies on the ¹⁴C signal produced by atmospheric nuclear weapons testing in the 1960s. The results showed that the largest examined specimen of the genus Democrinus was approximately 18 years old and its stalk grew at a rate of about 1.6 cm per year. These findings challenge the long-held assumption that deep-sea fauna are exceptionally long-lived and demonstrate that, in contrast to trees, growth rings cannot be used to reliably estimate the age of these animals.