The conodont animal is thus named because of its conodont 'teeth'. Having a vertebrate body plan and tissues derived from neural crest cells, this conodont animal is an early link between nonvertebrates and vertebrates. Though the above find may support the 'New Head Theory', other recent finds tend to support the 'Modification Theory'. Particular gene expression patterns have been found in similar head regions of vertebrate and nonvertebrate embryos. This finding favors the 'Modification Theory,' as it would be almost inconceivable for the same gene to evolve and express itself in similar regions of two different organisms.
Debate continues, however, regarding the actual mechanism for the evolution of the vertebrate head.
Genetic analysis may be the only way in which to end this debate. For example, the discovery of a gene that expresses itself in similar head regions of both Amphioxus and hagfish would highly support the 'Modification Theory'. Of course, finding and studying this gene is easier said than done. Nevertheless, this project is currently being undertaken here at the University of Oregon. Whatever the current research determines, and which ever mechanism prevails, we will still be left marveling at the structure called the vertebrate head.