Gram, Denmark — An associated set of gigantic vertebrae belonging to the iconic extinct Megalodon or megatooth shark that had been missing in action since the 1980s was discovered, providing new information about the shark's lifestyle. Two Museum of Southern Jutland staff, Mette Elstrup and Trine Sørensen, and a researcher at Aarhus University, Henrik Lauridsen, teamed up with a scientist in the United States and another in Australia and took a renewed look at a once-lost vertebral specimen of Otodus megalodon, the fossil shark that lived nearly worldwide about 15 to 3.6 million years ago. The new study appears in the international journal Palaeontologia Electronica.
The rediscovered 10.8-million-year-old vertebral specimen was originally discovered from a large commercially-dug clay pit in Gram, Denmark, in the late 1970s and was scientifically introduced in the early 1980s. The specimen was housed in the Geological Museum of Copenhagen (now part of the Natural History Museum of Denmark), but when the specimen was moved out of the original research laboratory after it was published, it became misplaced, leaving behind only photographic evidence in the scientific literature. The situation changed in the late 2010s when an observant museum staff member fortuitously encountered some mysterious fossil-filled boxes that were tucked in the collection and realized they were the missing Megalodon vertebrae.
Otodus megalodon is commonly portrayed as a gigantic shark in novels and films, such as the 2018 sci-fi thriller "The Meg." In fact, the most recent estimated maximum size of the fossil species is 24.3 meters in length, which possibly weighed about 94 tons. Although most of the vertebrae have deteriorated, their rediscovery is critical because it is the very specimen that was the basis of the maximum size and weight estimates.
"The rediscovery of the vertebrae was a true delight because they empirically confirm the maximum vertebral diameter of 23 cm reported in the literature," said the lead author of the new study, Kenshu Shimada, who is a paleobiology professor at DePaul University in Chicago. In fact, "the specimen not only represents the largest shark vertebrae known to date but also the largest fish vertebrae ever recorded to our knowledge," Shimada added.
Although no complete skeletons of Megalodon exist, the 24.3-meter estimate comes from its vertebral diameter compared with the maximum vertebral diameter (15.5 cm) measured from a reasonably complete string of trunk vertebrae known from Belgium, which is thought to have come from a 16.4-meter-long individual.
Sørensen, a Natural History Conservator at the Museum of Southern Jutland, who prepared the vertebral specimen, stated, "The sharks' cartilaginous skeletons make their preservation potential generally very low except for their highly mineralized teeth. The Gram Formation exposed in the claypit is special in that we have multiple examples of well-preserved fossilized shark vertebrae in addition to teeth from many shark species, although one known gigantic Megalodon tooth and the specimen in our study remain to be the only Megalodon vertebrae from the site."
Elstrup, the Head of the Natural History section of the museum, added, "The giant Megalodon vertebrae are of great importance because size matters when it comes to understanding the biology, ecological impact, and geographic distribution pattern of this extinct giant predator." "The Gram claypit site also represents the scientifically verifiable latitudinally highest Megalodon locality in the world, which does not contradict the previous observation that larger Megalodon remains are more common in 'cooler' regions relative to 'warmer' regions," Elstrup continued.
The research team took the study one step further by analyzing incremental 'growth bands' putatively formed annually (analogous to tree rings) in the Megalodon vertebrae using micro-CT imaging, a non-destructive X-ray-based technique. The micro-CT images revealed that the Megalodon individual was at least 64 years old when it died, with a possible theoretical longevity of 96 years old based on a growth model the team attained for that shark.
Lauridsen, an associate professor at Aarhus University, who performed the micro-CT scanning, noted, "Scanning the large, low-contrast vertebrae fossils surrounded by clay at ultra-high resolution was a real technical challenge, which resulted in generating more than 100 GB worth of images."
The team also made a surprising discovery. Upon closer inspection, the rocks surrounding the Megalodon vertebrae were found to contain many fragmentary gill-associated structures and tiny scales of another shark, the basking shark. Although the basking shark can grow to substantial sizes, the researchers ruled out the possibility that the vertebrae belong to the basking shark, because basking shark vertebrae are proportionally much longer than wider relative to Megalodon vertebrae and have been found in the same quarry.
"This led us to interpret the basking shark elements to represent the stomach contents of the Megalodon, which is the first documentation for the Megalodon fossil record," stated another coauthor, Mikael Siversson, who is a paleontologist at Western Australian Museum in Welshpool.
Deciphering the body size of large extinct carnivores like Megalodon, that must have had a significant impact on its ecosystem, is important in the context of ecology and evolution.
"Although our growth model suggests that Megalodon could have theoretically grown even slightly larger, the length of 24.3 meters is currently the largest possible scientifically justifiable estimate for O. megalodon," said Shimada.
This new study, "Rediscovery of the associated gigantic vertebrae of the extinct megatooth shark, Otodus megalodon, from the Upper Miocene Gram Formation in Denmark, and comments on its paleobiological significance and the maximum possible size of the species" authored by Shimada, Elstrup, Lauridsen, Sørensen, and Siversson will appear in the forthcoming issue of Palaeontologia Electronica and will be available online 12:01AM GMT on Monday, June 29, 2026 (= 8:01PM EST on Sunday, June 28).
