Evolution and Phylogeny of Pancrustacea

Book excerpt: "As a young and impetuous gradate student, I thought that sorting out the phylogeny of crustaceans would simply take but a little time and concerted effort to eventually reveal the truth. Everyone could then agree and further research would proceed apace. How naïve I was. First of all, I had never heard of Kurt Gödel's incompleteness theorems and hence the impossibility of achieving such an end. But even so, what progress we might have made turned out to take longer than anyone could have imagined, and the effort would be immense involving many people and a number of laboratories-and that task still continues. What no one could foresee in the 1960s was that the focus of everyone's attentions would completely transform. Traditional pure anatomy would be augmented with more sophisticated developmental genetic work. Concurrent with that effort molecular sequencing would become a remarkably effective tool. And with these new sources of data, the concept of "crustaceans" would yield to a new construct-Pancrustacea-within which the arthropods that we referred to by the name of "Crustacea" became a series of monophyletic smaller groups that mark a paraphyletic transition from a mandibulate ancestor all the way up to a crown group that few in the 1960s expected-Hexapoda emerged within the pancrustaceans"--