The species shown in the photo was named Alopias palatasi in 2018 by David Ward and myself in an addendum to my chapter on the fossil cartilaginous fishes of Calvert Cliffs published in Smithsonian Contributions to Paleobiology. The entire volume is available online (https://opensi.si.edu/index.php/smithsonian/catalog/book/107).

It certainly looks like a serrated thresher to me, as the serrations are too large for megalodon. The mesial cutting edge is broadly convex; in megalodon from similar tooth positions it would be more sigmoidal. Also, although the shape of the root lobes is typical of the giant threshers. The one odd feature is that the neck appears wide on the…[Read more]