Complexity trends in the evolutionary history of dasycladalean algae

Dasycladalean algae are a group of marine algae that have an excellent fossil record extending back more than 500 million years. In our study, we investigated morphological complexity over the evolutionary history of this group. To determine complexity for each of more than 400 species, we assigned numerical values for six morphological features; the sum for each species forms a quantitative expression of complexity. We found that although maximum complexity increased over time, forms with minimum complexity persisted during most of the evolutionary history of the group