Acrodus

Acrodus is an extinct genus of chondrichthyan, a group of cartilaginous fishes that includes sharks and rays. Fossils of Acrodus have been found in marine deposits dating back to the Triassic, Jurassic, and Cretaceous periods. This indicates that Acrodus was a successful and widespread fish group for a considerable span of geological time.

The genus Acrodus is characterized primarily by its teeth. These teeth are typically small, blunt, and rounded, often described as button-like or acorn-shaped. This morphology suggests that Acrodus was not an active predator of large, fast-moving prey. Instead, its dentition is indicative of a diet consisting of hard-shelled invertebrates, such as mollusks and crustaceans. Acrodus likely used its teeth to crush or grind these hard-shelled organisms.

Fossil remains of Acrodus are relatively common in certain formations, though they are often disarticulate, meaning individual teeth are found rather than complete skeletons. This is typical for many fossil sharks and rays, as their cartilaginous skeletons are less likely to preserve than calcified bones. The distribution of Acrodus fossils suggests it inhabited shallow marine environments. While its exact phylogenetic position within the chondrichthyans is debated, it is generally placed within the extinct order Hybodontiformes, a group of sharks that flourished during the Mesozoic Era.