Everyone loves animals, and almost all of the animals you realize are vertebrates. Hannibal and Patel make the excellent point that there is no merit in talking about segmentation without being specific about what is being mentioned. It is extra correct and useful to debate how somites form, how rhombomeres emerge and the way pharyngeal arches are generated. The second problem is the relative paucity of segmentation within the bilateria and its implications. As Hannibal and Patel level out, if segmentation is difficult to evolve, this may suggest that it had a single origin however that it was subsequently lost by the nice majority of animal phyla and solely retained in a couple of .
One conclusion following from this hypothesis would be that segmentation is readily dispensable within the era of a useful body plan. By contrast, if segmentation is relatively simple to evolve then one would anticipate to … Read MoreRead More »