Quick summary: The rediscovery of a long-lost set of 10.8-million-year-old fossil vertebrae in Denmark has provided unprecedented insights into the biology of the prehistoric megatooth shark Otodus megalodon, establishing a new scientifically justifiable maximum length of 24.3 metres. High-resolution micro-CT imaging of the record-breaking specimen revealed that the individual lived for at least 64 years, while the presence of basking shark scales within the surrounding rock matrix offers the first historical evidence of the predator’s actual stomach contents. For public education and scientific well-being, these findings fundamentally reshape our understanding of marine evolution and ecological balance, demonstrating how ancient environmental shifts towards cooler climates directly influenced the body mass and geographic distribution of the planet’s largest apex carnivores.
A set of enormous fossil vertebrae from the prehistoric megatooth shark Otodus megalodon, missing since the 1980s, has been rediscovered in museum collections in Denmark, providing fresh insights into the biology and maximum possible size of one of the largest predators to have ever lived.
The 10.8-million-year-old vertebral specimen was originally excavated from a large commercially dug clay pit in Gram, Denmark, in the late 1970s. It was scientifically described in the early 1980s and housed at the Geological Museum of Copenhagen, now part of the Natural History Museum of Denmark. After its initial publication, the specimen was moved from the research laboratory and subsequently misplaced, surviving only as photographic records in the scientific literature.
In the late 2010s, an observant member of staff at the Museum of Southern Jutland came across mysterious fossil-filled boxes in storage and identified them as the long-lost Megalodon vertebrae. Two Museum staff members, Mette Elstrup and Trine Sørensen, together with Henrik Lauridsen of Aarhus University, collaborated with Kenshu Shimada of DePaul University in the US and Mikael Siversson of the Western Australian Museum in Australia. Their renewed study of the specimen has now been published in the international journal Palaeontologia Electronica.
Record-breaking dimensions
Otodus megalodon is widely known from popular culture, including the 2018 film The Meg, as a gigantic shark. The most recent estimated maximum size for the species is 24.3 metres in length, with a possible weight of about 94 tons.
“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 lead author Shimada, a paleobiology professor at DePaul University in Chicago. “The specimen not only represents the largest shark vertebrae known to date but also the largest fish vertebrae ever recorded to our knowledge.”
No complete skeletons of Megalodon exist. The 24.3-metre estimate derives from comparing the vertebral diameter of the Danish specimen with the maximum vertebral diameter of 15.5 cm from a reasonably complete string of trunk vertebrae from Belgium, where that individual is thought to have measured about 16.4 metres in length.
Preservation and site significance
Sørensen, a Natural History Conservator at the Museum of Southern Jutland who prepared the vertebral specimen, noted the rarity of such a find. “The shark’s cartilaginous skeletons make their preservation potential generally very low except for their highly mineralised teeth. The Gram Formation exposed in the clay pit is special in that we have multiple examples of well-preserved fossilised shark vertebrae in addition to teeth from many shark species, although one known gigantic Megalodon tooth and the specimen in our study remain the only Megalodon remains from the site.”
Elstrup, 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 clay pit 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.”
Age and growth findings
The team examined incremental growth bands, thought to form annually like tree rings, using micro-CT imaging. This non-destructive X-ray technique showed the individual was at least 64 years old at death, with a possible theoretical longevity of up to 96 years based on the growth model developed.
Lauridsen, who performed the micro-CT scanning at Aarhus University, 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.”
Stomach contents identified
A further discovery came from the surrounding rock matrix, which contained fragmentary gill-associated structures and tiny scales of a basking shark. While basking sharks can reach substantial sizes, the researchers ruled them out as the source of the large vertebrae because basking shark vertebrae are proportionally much longer than wide compared with those of Megalodon, and have also been found at 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 in the Megalodon fossil record,” stated co-author Siversson.
Understanding the body size of large extinct carnivores such as Megalodon, which would have exerted a major influence on marine ecosystems, holds significance for studies in ecology and evolution.
“Although our growth model suggests that Megalodon could have theoretically grown even slightly larger, the length of 24.3 metres is currently the largest possible scientifically justifiable estimate for O. megalodon,” said Shimada.
The full paper, titled 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, is authored by Shimada, Elstrup, Lauridsen, Sørensen, and Siversson, and appears in the forthcoming issue of Palaeontologia Electronica.