The largest fishy predator ever to prowl the world's oceans may have been even more gargantuan than past estimates suggested. The finding, published in Palaeontologia Electronica, is an unexpected outcome of a program to get high school students interested in science, and the dedication of a post-graduate student intrigued by their contradictory findings.
Entire specimens of extinct animals are seldom found, so paleontologists have developed formulas for estimating size based on single bones or, in extreme cases, teeth. Megalodon's name literally means “big tooth” because, a few vertebrae aside, that is all we have left of them. Sharks' cartilage, which replaces most of the bones in other vertebrates' bodies, rarely fossilizes. In 2002, equations were published for calculating the sizes of giant extinct sharks from their teeth, including megalodons, which dominated the oceans for 20 million years, and others larger than any survivors.
While doing his PhD at the Florida Museum of Natural History Dr Victor Perez realized these calculations could be turned into a particularly interesting science project. Perez collaborated with middle-school teacher Megan Hendrickson to have her students 3D print replicas of real megalodon teeth, measure them, and use the formulas to calculate the size of the giant they came from.
When Perez looked at their results, however, he found the students were getting wildly different answers that couldn't be attributed to measurement errors. Some thought the shark was 12 meters (40 feet) long, which would be immense enough, but others produced an estimate of 45 meters (148 feet). The latter figure would have made it almost one and a half times the length of the longest blue whale.
Perez started with the obvious explanations. "I was going around, checking, like, did you use the wrong equation? Did you forget to convert your units?” he said in a statement. "But it very quickly became clear that it was not the students that had made the error. It was simply that the equations were not as accurate as we had predicted."
Faced with a nearly complete set of teeth, the students had made choices as to which they should use for their calculations. Although in theory the formulas allowed for varying size by tooth location, Perez found the further back in the jaw a tooth was, the larger the size calculated for the fish it came from.
Others might have ignored the issue, but Perez reported the outcome in a newsletter read by fossil researchers and amateurs. Amateur paleontologist Teddy Badaut read the account and suggested tooth width might provide a more accurate estimate of shark size than length. After all, the combined width of all the teeth provides an approximation of jaw size.
Perez and colleagues worked on finding equations relating the width of teeth from living sharks to their size and extrapolating to their extinct relatives. In the study, they report these produce much more consistent estimates for shark body length.
Width may matter more than length, but Perez acknowledges; “We haven't really settled the question of how big megalodon was.”
Nevertheless, the range has been narrowed, suggesting the largest teeth found came from creatures 17–24 meters (55–75 feet) long. Although this overlaps with previous estimates, it is larger than most (those made by Hendrickson's students working on back teeth aside), confirming these giants were two to three times the length of the largest living white sharks.
Sequels to The Meg should call Perez as a consultant in the unlikely event the makers care about scientific accuracy.