I wanted to continue this discussion without completely hijacking Jon's thread... The next question I have is whether the genetic analysis might be able to indicate when this egg-laying habit was lost (or gained) and how that timing related to the development of a bottom-dwelling life (or do I have that backwards too?) and the loss of a shell. Seems like you might not need to lay as many batches of eggs when you have the ability to crawl into well-hidden, easily defendable spaces. Maybe?