macroevolution

The paper focuses on the macroevolution of crinoids in response to sea urchin predation. Although sea urchins are more commonly known as grazers and predators that feed on coral, evidence of sea urchin bite marks on crinoids suggests a predator-prey relationship between the two. The data collected by the authors shows that bite mark frequencies increased with sea urchin diversity. It also showed that frequencies of bite marks on sessile crinoids was higher than those of motile crinoids. This result suggests that crinoids evolved to become motile as an evolutionary response against sea urchin predation during the Triassic. It also provides an explanation for why motile crinoids are more abundant than sessile crinoids in recent history. Overall, sea urchin predation on crinoids was measured by bite-mark frequencies, and the predator-prey interaction led to macroevolutionary changes in crinoids.