Research Shows that Sea Urchins, Sand Dollars Thrived with Time
A new study about echinoids—marine animals like sea urchins and sand dollars—gives scientists a reason to rethink a classical pattern of evolution. Fossil-based studies have traditionally indicated that groups of organisms diversify fastest early in their evolutionary history, followed by a steady decline through time. But the new work on Echinoidea, published this week in the Proceedings of the National Academy of Sciences, contradicts that expectation, showing that rates of evolution were actually lowest at the group’s onset and increased over time through episodic bursts associated with changes in the animals’ feeding strategies.