Eventually, when I finish my current projects, I will get around to discussing conodonts, and their jaw-like … things. But for the moment, I’d like to call out to the various sources on the latest paper (not yet published in print in the journal Proceedings of the Royal Society, B: Biological Sciences, but available online, here) that has been receiving attention [Taylor Reint’s consideration, a Nature blog, and a Scientific American blog treatment] due to the results of finite element analysis (FEA) on one of the posterior P elements of conodonts. First, conodonts are jawless; like lampreys and hagfish, they lack an actual mandibular or even palatoquadrate-like structure. These did not develop until the younger lineages of the gnathostome variety, and even then were very different from what WE might term “jaws.” They possessed a muscularly-controlled oral aperture, but in many ways this was formed by an arrangement of lobes that were supported on the inside by jaw-like, stiffened or calcified objects, as in lampreys. These might be termed “teeth,” and they might also have “tongues” with more stiffened strictures embedded in them, but they possess numerous features that obscure their homology or in fact indicate they were not homologous at all to our “jaws” and “teeth”. Thus, to call them “jaws” and “teeth” seems misleading. The conodont apparatus is one of the most interesting, and fascinating structures in chordate evolution, given that it was essentially abandoned when these tiny creatures went extinct, and no further chordate lineage has developed something even remotely similar. Yes, osteichthyans like chondrichtyans and lungfish often have elaborate pharyngual bones and teeth, gill rakers that projected inward and operate in many ways similar to some conodont arrays, but the massive variety of structures do not actually possess homology with that of the conodonts, even if they were anaologous.
This is not a criticism of the paper in question, but in many ways of the news releases involved. I know that Dr. Philip Donoghue, who has spent a fair amount of time studying the conodont apparatus and in the last decade published several papers with Dr. Mark Purnell, attempted to emplace the various S, M, and P elements into their correct positions and to assess their function and available motions. These studies indicate that the conodont apparatus is so uniquely interesting that to use the terms “jaws” and “teeth” for these structures is to overly simplify and obscure the amazing apparatus and its evolution, otherwise relegated to obscure papers in micropaleo journals. These animals may be so fascinating, that “jaws” and “teeth” do not do them justice.
(Yes, I realize that “teeth” is often being applied as are the “teeth” of combs: the term “denticle” and “cusp”, however, are used extensively in the paper, as “correct” terms, and I understand to relate to the laity or unspecialized public, “tooth” is a useful analogy.)
This is just a gripe, and I mean nothing ill of the persons who have perpetrated this horrible miscarriage, this horrendous mockery, this — checking thesaurus — heinous mistake.
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License (the second figure, from David Lynch’s Dune(1984, Dino De Laurentiis Co., distributed by Universal Pictures) is certainly not the property or product of the author).