A few years ago, a book came out by Jack Horner, entitled How to Build a Dinosaur.(http://search.barnesandnoble.com/How-to-Build-a-Dinosaur/Jack-Horner/e/9780452296015) In order to spare you a few dollars (although I would definitely still recommend it to any that haven't read it), I am going to quickly summarize the main points, and what they have to do with cephalopods. The statement "Ontogeny recapitulates phylogeny" is no longer accepted as true. The principle, though, is at least slightly valid. While not every stage in the evolution of an organism is displayed during development, many past traits are. When traits disappear or change, the genes coding for them usually aren't deleted, merely switched off by the creation of new genes. Every gene causes a cascade of effects, meaning that they each affect the expression of maybe (just throwing a random number out) a dozen other genes, which in turn affect a dozen more genes, and so on. This means that, to simplify it, newer DNA is built on top of older DNA. Often, newer genes are not switched on until partway through the development of an embryo. A man named Hans Larsson, at McGill University, is working on finding the point in the development of chicken embryos at which the formation of the characteristic therapod tail halts and instead leaves the chicken with a pygostyle (stumpy, non-muscular, chicken-style tail). Once that is done, he intends to determine what changes occur in the biochemistry of the embryo at that, and by reversing them, prevent the inhibition of development of a muscular tail. This process has already been done with teeth. Granted, the chickens didn't hatch, but they did develop teeth. Apparently, since the introduction of the genes involved in building a beak, so much has been built on top of them that switching them off prevents the development of a functional chicken. However, teeth did develop before the embryos died, and they were consistent with those of other archosaurs. Now, for the fun part. Given the obvious facts that cephalopods are not exactly the same through every stage in their development, and that their DNA builds on top of itself just like that of everything else, this process for recreation of archaic traits should be just as possible in cephs as in chickens. It would be theoretically possible to reconstruct archaic nautilus traits in modern nautilus. It would also be possible, theoretically, to simply monitor changes in various elements of the biochemistry in the organism throughout development, and select and reverse several of them, one at a time, and thereby prove that certain traits were posessed by the ancestors of the organism at some point. One would have to be careful in doing that, though, as it would be quite possible to generate something not within the evolutionary history of the organism, by having combinations of genes switched on at the same time that weren't prehistorically, thus producing unique traits that weren't present in the ancestors of the organism. However, it would be possible to work around this by simply using the fossil record for confirmation of being "on the right track". Given the considerable gaps in the fossil record, it would be wise to have a backup. Perhaps one could confirm that the traits produced were not affected by later genes by working backwards through the biochemical changes; starting with those latest in development and then working earlier from there. This would, of course, take quite a while to work back to a trait of any significant distance from the present era. Also, in order to ensure that the newer genes aren't affecting the development of older traits, they would have to be switched off independently for each test. Switching them off biochemically, without actual manipulation of genetic material, would be the only feasible method of achieving this, as adding new to genes to switch them off could affect the expression of the older genes, and removing the genes completely could be difficult. Therefore, unfortunately, the process of switching off genes manually would have to be repeated each time, and would greatly increase the farther back you went. It would, though, (looking on the bright side) be possible, and it wouldn't really be enormously surprising (if still very impressive) if someone on Tonmo managed it to a certain degree. Please, keep in mind that I am not an expert on genetics or cephalopods. If you find any errors, feel free to point them out.