Physogaleus

Physogaleus is an extinct genus of small requiem shark that lived from the Late Paleocene to Miocene epochs.

Description
Physogaleus is only known from fossil teeth and isolated vertebra. The teeth similar to those of the modern Tiger shark, but are smaller, with a more central cusp that projects farther from the base of the tooth. The species of Physogaleus were originally described as belonging to the same genus as the modern Tiger shark, Galeocerdo. Recognition of numerous differences in dental anatomy of each these species compared other species of Galeocerdo lead researchers to erect the genus Physogaleus to include taxa that were more morphologically similar to one another than they were to Galeocerdo.

Physogaleus teeth reach a maximum size that is smaller than that of true tiger sharks, and they lack the heavy serrations typical of Galeocerdo. They are also are more slender and the central cusp can be somewhat twisted toward the crown. This indicates individuals of Physogaleus probably had a diet of bony fish, similar to the living sand-tiger shark.