Just when you thought it was safe to jump into your time machine, travel back 20 million years and go for a swim, researchers have discovered about a dozen 20-million-year-old fossilized teeth of a newly identified extinct shark that was a close cousin of Megalodon, the super-predator megatoothed shark that some estimate reached a length of 18 meters (59 ft) during its reign of underwater terror. Was Megalolamna paradoxodon another big-toothed terror? And what’s with the paradoxical name?
According to a new study in Historical Biology, 1.8-inch-long (4.5 cm) teeth were found in Peru, Japan and California and North Carolina in the U.S. The teeth matched each other but no other known shark species of the early Miocene epoch. They had some qualities of the megalodon family (Otodontidae) and some qualities (their big size) of the Lamna family of mackerel sharks which includes salmon sharks, mako sharks and the great white shark. As a result, Kenshu Shimada, a paleobiologist at DePaul University and author of the study, decided it was a new genus, Megalolamna.
The species name “paradoxodon” (meaning paradoxical teeth) comes from the fact that the shark appeared suddenly and there’s no indication when it split from the Otodus family of sharks with otodus (Greek for ear-shaped) teeth. Shimada says this also indicates that the megalodons (Carcharocles megalodon) properly belong in the Otodus group and as a result are not the direct ancestor of the great white shark (Carcharodon carcharias).
Confused? Let’s get back to the Megalolamna paradoxodon. While a cousin of the megalodon, Megalolamna was relatively smaller, reaching a maximum length of around 10 meters (33 ft). That’s not quite a bus but still bigger than today’s great whites at 4 meters (13 ft). They had grasping-type front teeth and cutting-type rear teeth to eat medium-sized fish.
While it seems to have reached extinction relatively quickly, Megalolamna paradoxodon still covered a lot of territory, most likely due to its size and lack of predators – Shimada doesn’t believe that megalodons ate megalolamnas. The extinction of both species was probably due to a combination of global cooling, declining fish supplies and the emergence of predators such as killer whales.
Fortunately, we still have great whites … for now.