Monstrous megalodon was a slow swimmer with big appetite, finds study

“Our big scientific findings come from ‘tiny evidence’ as small as grains of sand,” said Shimada in an official release.

Until now, the biology of these ancient sharks has been primarily deduced from their massive tooth and vertebral relics.

The lack of "narrowly-spaced ridges or keels" on the placoid scales led to the conclusion that they were not a fast swimmer. One of the characteristics of fast-swimming sharks is the presence of keels. 

“This led my research team to consider O. megalodon to be an ‘average swimmer’ with occasional bursts of faster swimming for prey capture,” added Shimada.

The species devoured large animals 

These new findings also create a new paradox. The species was thought to be partly warm-blooded or regionally endothermic. Recent investigations have also presented the same conclusion. 

The new research raises the question of how the species managed to expend the high metabolic heat associated with its warm-bloodedness without being a fast swimmer.

To find questions to this paradox, the team reviewed body physiology literature. It turns out that O. megalodon had a massive appetite. 

 “Otodus megalodon must have swallowed large pieces of food, so it is quite possible that the fossil shark achieved the gigantism to invest its endothermic metabolism to promote visceral food processing,” said Shimada. 

Simply put, despite being a slow swimmer, the monstrous creature used its warm-bloodedness to aid digestion and nutrition absorption. 

This vicious predator preyed on marine animals such as whales, seals, and huge fish. It might have reached a length of 65 feet (20 meters). 

Because of its iconic size, the species made its way to Hollywood, where it appeared in the sci-fi thriller "The Meg" and the upcoming "Meg 2." 

The details of this new study have been reported in the journal Historical Biology.

Study abstract:

The late Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), is mostly known for its gigantic teeth and vertebrae. Re-examination of the rock matrix surrounding a previously described associated tooth set of O. megalodon from the upper Miocene of Japan resulted in the observation of numerous fragments of tessellated calcified cartilage and placoid scales. The morphology of each tessera and the arrangement of overall tessellated calcified cartilage are practically identical to those of extant chondrichthyans. Many placoid scales possess pronounced, rather broadly-spaced keels. A quantitative relationship between interkeel distances of keeled scales and reported cruising speeds across extant pelagic lamniforms and carcharhiniforms suggests that O. megalodon with a representative interkeel distance of ca. 100 µm was not a fast swimmer. We propose that O. megalodon was generally a slow cruising shark with occasional burst swimming for prey capture, where much of its metabolic heat through regional endothermy was possibly used to facilitate the digestion of large pieces of ingested meat as well as absorbing and processing nutrients. If so, the relative importance of the functional roles of regional endothermy possibly shifted from maintaining high cruising speeds to visceral food processing through the evolution towards gigantism in otodontids.