The family of mackerel sharks, from the modern mako to the prehistoric megalodon, can be traced back to a modest common ancestor, according to a new study by the University of Vienna, Austria.
The study, which was published in the recent journal Scientific Reports, looked at tooth samples from the great white and other members of the mackerel shark family. They found that a certain characteristic — osteodentine roots intruding into the crown of the tooth — was shared by ancestors dating back to the middle jurassic period some 165 million years ago.
By using this unique characteristic to establish an evolutionary map, the researchers were able to date the modern mackerel sharks ancestry all the way back to the fossil shark Palaeocarcharias stromeri, a relatively small, sluggish benthic shark similar to modern carpet sharks, that only grew to a length of about three feet.
According to the researchers, the shared tooth histology is a strong indicator that this small inconspicuous shark gave rise to one of the most iconic shark lineages that includes giants like the extinct Megalodon or the living great white shark.
“Orthodentine is known for almost all vertebrates—from fish to mammals, including all modern sharks, except for the mackerel sharks. The discovery of this unique tooth structure in the fossil shark Palaeocarcharias strongly indicates that we found the oldest known ancestor of the great white shark and shows that even this charismatic giant shark started on a shoestring,” says Patrick L. Jambura.