In the first study of its kind, graduate student Alexandra Krak and Biological Sciences Professor Kenshu Shimada have used an innovative method to reconstruct the dentition of an extinct megamouth shark, known as Megachasma applegatei. The shark would have lived sometime in the late Oligocene and early Miocene periods in the western United States (about 23-38 million years ago). Only single teeth from the shark have been isolated, making reconstructive modeling helpful in learning about the animal's anatomy.
Krak used a novel method to model the shark's teeth.In their recently published study, Krak and Shimada used a technique known as geometric morphometrics to approximate the dental structure of the shark. To do this, variations of teeth in existing lamniform shark species were compared with over 200 isolated teeth from M. applegatei collected from the lower Miocene Jewett Sand region of southern California. Lamniform sharks include some of the world's most familiar species, such as the Great White. To determine whether M. applegatei had a typical lamnoid tooth pattern, its teeth were photographed, measured, and compared with two other species before generating scatter plot diagrams to map the distribution of tooth types/features. “We used Odontaspis ferox, the smalltooth sandtiger shark, since it possesses a good representation of the 'lamnoid tooth pattern' and Megachasma pelagios, the extant sister species of M. applegatei which is a planktivorous shark for comparison," explains Krak.
To get the closest approximation, three sets of upper and lower teeth were reconstructed featuring different tooth arrangements. The results of the research indicate that M. applegatei likely did have a lamnoid tooth pattern, with its characteristics falling somewhere between the two other species evaluated. The findings offer a crucial window into an otherwise inaccessible past and can serve as a definitive reference until an intact model of the shark's teeth is found. The full study was published in PaleoBios and can be found here.