A quick look at the fossil record shows that no species lasts forever. On average, most species exist for around a million years, although some species persist for much longer. A new study shows that young species can take advantage of new opportunities more easily than older species, a hint that perhaps older species are bound to an established way of life. For the study, the research team's best choice for tracking the change was a peculiar family of marine animals known as the cupuladriid bryozoans. These relatively small animals consist of unusual, free-living, disc-shaped colonies of individuals called zooids. The research team collected and identified more than 90,000 cupuladriid colonies from 200 fossil samples and 90 more recent samples collected by dredging the sea floor. The samples contained mud, sand, coral remains and other indicators of the kind of habitats where the bryozoans had lived. Shown here: Stiff setae extend away from the edge of cupuladriid bryozoan colonies and work in synchrony to allow the colony to "walk" over the seafloor.
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