I've found that many paleontologists have been loose and fancy-free with batoid teeth. The paleontological genera "Raja", "Dasyatis" and particularly "Myliobatis" are catch-all buckets. The only author (available to me) that appeared to make an attempt, to seriously differentiate these teeth, was Henri Cappetta (1987). Identifying Miocene batoid teeth from Lee Creek was a challenge.
Using Cappetta as a guide, attention was directed to teeth of living batoids. Most ichthyologists studying extant batoids pay/paid little attention to the odontological design of the teeth -- Herman, et al, (1986-present), Notarbartolo di Sciara (1987) are exceptions, Other than functional studies or cursory descriptions of the dentitions (i.e. Bigelow & Schroeder, 1953) there is a distinct void in the information available on the teeth of extant batoids.
With little background material available on the subject, I started looking at batoid dentitions, taking notes and making sketches. This early research first appeared in a series of articles in the NJPS Paleontograph. Subsequent research has become more detailed. The accompanying webpages track this evolution of this research and may prove useful to others following a similar tact.