According to foreign media reports, the extinct giant toothed shark is the largest predatory shark in history, and the great white shark is currently the largest predatory shark. It turns out that the ancestors of both sharks may have been a small, flat shark.
Other sharks, such as giant toothed sharks and great white sharks, are members of mackerel sharks, also known as Lamniformes. One of the reasons why these sharks are different is their teeth.
Shark teeth consist of hard mineralized cystic shells surrounding the dentin core. Conversely, dentin is usually composed of two types - the orthodontic dentin confined to the crown, and more bone teeth, which exist in the root and sometimes in the crown. It is used to support orthodontic dentin when there is additional bone in the crown.
However, in a recent international study led by Patrick L. Jambura of the University of Vienna, CT scans of mackerel shark teeth showed that in their case, bone teeth extended from root to crown, completely replacing orthodontics as the only dentin type in teeth. Looking back at the fossil record, the only one showing this tooth is a shark called Palaeocarchariasstromeri (shown below).
The shark is no longer than a meter (3.3 feet) long and may have hunted small fish in shallow water 165 million years ago. It is flat, similar to modern whisker sharks living in shallow water. Although it has little in common with mackerel sharks, it is now considered to be their distant ancestors.
Orthodontics are present in almost all vertebrates, from fish to mammals, including all modern sharks, except mackerel sharks, Jambura said. The discovery of this unique dental structure in Palaeocarcharias shark fossils strongly suggests that we have discovered the oldest known ancestor of the great white shark, and that even this giant shark with extraordinary charm is the same.
Scientists recently published a paper on the study in the Journal Science Report.