The planktivorous sharks (Rhincodon typus, Cetorhinus maximus, and Megachasma pelagios) filter zooplankton using elaborate branchial filters. Each filter-feeding shark retains large numbers of highly curved teeth (ex. 300 rows in whale shark, 100-150 rows in basking shark, and 90 rows in megamouth). We ask, are these teeth vestigial structures or are they functioning in a similar manner as placoid scales. Our study used anatomical measurements of teeth from the three planktivorous sharks (height, width, spacing, and surface curvature) to build, 3-D physical and computational models. We found that tooth shapes and spacing are vastly different among species. The filter-feeding sharks’ teeth are convergent in form and greatly differ from their closest extant relatives. For example, Stegostoma fasciatum teeth are relatively straight and tricuspid, while the closely related whale sharks have a curved, singular cusp. Previous work on placoid scales (dermal denticles) showed that a ratio of height to spacing (H:S) of 0.5 and a ratio of thickness to spacing (T:S) of 0.03 produces maximum drag reduction. The higher H:S and T:S ratios in whale sharks and basking sharks should result in an increased drag (H:S = 1.75, T:S = 0.33 and H:S = 0.68, T:S = 0.86 respectively). Megamouth shark has a lower H:S ratio; however, the higher T:S ratio should also result in increased drag (H:S = 0.27, T:S = 1.79). Increased drag at the mouth opening may help to laminarize flow directed toward the anteriorly located filter elements. Laminarized flow across the filters promotes both cross-flow and ricochet filtration during feeding events.