DECEMBER 2014 | TRILOBITE TALES 15 IMAGING TECHNIQUES FOR STUDIES OF MICROWEAR ON EDESTUS TEETH by Wayne M. Itano Introduction In 2013 I received a Karl Hirsch Memorial Grant of $500 from WIPS to support a project titled “Functional morphology of Edestus teeth, based on observations of microwear.” One of the conditions of accepting the award is to present results of the study to the WIPS membership, either as an oral presentation or an article in Trilobite Tales, within two years. This article is meant to fulfill that requirement. The research is still in progress. I expect to submit the significant results in the form of an article in a scientific journal, in which WIPS will be acknowledged. Unlike in a typical scientific report, I will give some detail as to how the $500 was used. WIPS does not ask for such an accounting, but I think it might be of some interest to WIPS members, including those considering applying for a grant. Research question: Edestus is a shark from the Pennsylvanian Period that has a unique dentition, consisting of two tooth whorls containing sharp, serrated teeth. It is generally thought that these tooth whorls acted like scissor blades to cut prey caught between them. The problem with this idea is that the tooth whorls are curved, so that only a few of the teeth can be brought together, and the outer ones don’t seem to be functional. One recent reconstruction is shown in Fig. 1. In this reconstruction, the shark cannot close its mouth, and most of the sharp teeth cannot be brought together. I have proposed a new reconstruction that allows Edestus to close its mouth, but leaves the tooth whorls extending outside the mouth. Rather than cutting prey between the two tooth whorls, I propose that Edestus slashed prey with an up-and- down motion of the entire head, with jaws fixed, as in Fig. 2. So, which reconstruction is closer to the truth? Did Edestus use its teeth like scissors or to slash? Figure 1 – A reconstruction of Edestus giganteus. From the 2013 book, “Requins: De la préhistoire à nos jours.” by G. Cuny and A. Bénéteau. Drawing used with permission. Figure 2 – New idea for the use of the tooth whorls. The head moves up and down, with jaws fixed, to slash prey. This drawing is for Edestus newtoni. Drawing by Gary Raham.