Macroevolution of Crinoids

The main point of this paper is that sea urchin predation caused macroevolutionary changes in crinoids. 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. Data collected by the authors show 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. The authors of the study hypothesize that crinoids evolved motility as a response against sea urchin predation during the Triassic. This conclusion seems plausible because motile crinoids have become 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.