For 40 million years, fern - like organisms called rangeomorphs ruled the world, because their branching bodies made them perfect diffusion feeders (newscientist.com)
This means that the sudden appearance of rangeomorphs at large size could have been a direct result of major changes in climate and ocean chemistry. (sciencedaily.com)
Since rangeomorphs don't resemble any modern organism, it's difficult to understand how they fed, grew or reproduced, let alone how they might link with any modern group. (sciencedaily.com)