I have now fully read this new Jan 2024 study, and find it interesting and thought-provoking, but also believe that significant additional research is needed. And, I find it remarkable that the authors failed to even mention the far larger Megalodon vertebral centra that have been found of a large but not maximum size Megalodon (the Denmark specimen) with a max vertebrate diameter of 23 cm. (Additional evidence such as the Honninger/Peru skeleton also potentially suggests that centra diameter could be substantially larger than 23 cm. I will discuss in further posts). Instead the authors' analysis exclusively relies upon the incomplete and smaller vertebral centra in the approximately 140 vertebrates found in the Belgium specimen with a maximum diameter of about 15.5 cm. In the upcoming days, I will have additional and more detailed comments, praise, and criticism of this study in further posts.
But first I wanted to post some interesting and pointed criticisms/reactions of the study by Jack Cooper (and others), who of course this current study is trying to rebut. Certainly there is polite but very sharp scientific disagreement going on here.
www.washingtonpost.com/science/2024/01/21/megalodon-slender-great-white-shark/
But both teams have pointed critiques of each others’ studies, a normal — if sometimes uncomfortable — part of how science moves forward.
Jack Cooper, a graduate student and shark paleontologist at Swansea University in Wales who led the study that is under attack, said that his team’s work has been criticized because of its overreliance on the great white shark as an analog to megalodon. But the new interpretation originates from an analysis that also relies on comparison to a great white.
He also disagreed that a thin backbone would necessarily be too narrow to support a bulky animal,
pointing out that the extinct shark cretoxyrhina also had a slender vertebral column but a bulky body form. (emphasis added)
Outside experts said both papers still use speculation to arrive at their different interpretations.
“At the end of the day, I don’t think it brings us that much closer to knowing what megalodon really looks like,” said Robert Boessenecker, a coastal paleontologist at the nonprofit Charleston Center for Paleontology who was not involved in the new study.
Dana Ehret, curator of natural history at the New Jersey State Museum, said that it was good to see biologists who study modern shark biology join the discussion of ancient sharks, and, for him, the interesting thing is that both papers suggest that the megalodon was probably longer than scientists once thought.
Jack Cooper says the new publication doesn't supply sufficient evidence to support a more svelte Megalodon. He's a graduate student in paleobiology at Swansea University in the UK. He's part of that other group that measured the spine and came up with the longer estimate of Megalodon's length.
Cooper says the new publication presents an argument his group already considered. "It does reaffirm that we would need to find a complete skeleton to know for sure what Megalodon looks like," he says. "But if you're going to present an alternative hypothesis, you should use a lot of statistical work to try to make your case."
Cooper agrees this is an important riddle to solve, once more fossil evidence becomes available. That's because Megalodon likely kept its most essential organs warmer than the surrounding seawater, which would have allowed it to swim further and faster.
Knowing its size and body shape tells us how much it likely had to eat to maintain such a lifestyle. "And that can tell us quite a lot about what made it vulnerable to extinction about 3 million years ago," says Cooper.
At the end of Megalodon's reign, sea levels were changing, ruining coastal habitats. This would have meant less food, possibly contributing to the giant shark's extinction. Cooper says the reasons behind Megalodon's vanishing could help us respond to the plight of today's sharks, many of which are endangered on a planet again in flux.
www.npr.org/2024/01/26/1226649080/that-giant-extinct-shark-megalodon-maybe-it-wasnt-so-mega
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The authors of the previous study are not convinced by the new findings, however. Lead author Jack Cooper, a researcher at Swansea University in the U.K., along with his colleagues Catalina Pimiento, also at Swansea University, and John Hutchinson, at the Royal Veterinary College, say the new study is more of an alternative hypothesis that suffers from "circular logic" — where an argument assumes its conclusion is correct, and uses the conclusion to support the argument
"Moreover, they don't actually provide a new length estimation in their work," they told Live Science in an email. The new study, they added, ignores the fact that the previous analysis considered multiple living examples of sharks alive today, and that one of their models also showed an elongated body when based on great white sharks alone.
"Importantly, the 'elongated body' interpretation is based on a single observation, a comparison with a single analogue, and lacks any statistical tests to support its hypothesis," they said. "More critically, several aspects of the study are impossible for future researchers to verify or replicate as the authors do not provide the raw data."
www.livescience.com/animals/extinct-species/controversial-study-claims-megalodon-didnt-look-like-a-50-foot-giant-great-white-shark
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But the researchers behind the 2022 research are not convinced by the new hypothesis. “While alternative hypotheses should be and are welcomed in science, this particular proposal suffers from a circular logic,” says paleontologist Jack Cooper of Swansea University in Wales, who was not involved in the new study.
The new study says that the great white shark is an inappropriate analogue for O. megalodon, Cooper notes, but the new research also uses the great white shark for its comparisons of body form to the exclusion of other sharks. The 2022 study, by comparison, considered other lamniform sharks in addition to the great white and created a three-dimensional model. The 2022 study also produced an elongated O. megalodon model as one of its possible outcomes, as well, but researchers ruled it out based on data from a broader array of lamniform sharks.
Lacking a complete O. megalodon skeleton, such disagreements may seem difficult to resolve. “However,” Cooper says, “sharks have generally remained geometrically similar throughout their long evolutionary history, which means living sharks can be informative in reconstructing extinct ones.” Even when the shark’s record is mostly teeth and isolated vertebrae, scientists can still generate a rough idea of the megatooth’s shape based on physiology, what it likely fed on and other details gleaned from the fossil record.
Working out the shark’s form is critical to understanding how the megatoothed shark lived during its long tenure in Earth’s seas. “The body plan of megalodon is a key part of understanding its wider ecology, such as how fast it swam and what it needed to eat,” Cooper says. A longer shark would swim differently, for example, or have organs like the liver and spiral intestine related to the shark’s feeding and digestion. O. megalodon thrived for about 20 million years before vanishing, even as its preferred prey survived. Understanding the shark’s form can help experts uncover the carnivore’s evolution and extinction.
For the moment, however, Cooper and colleagues are not swayed by the new reconstruction. All researchers are agreed that O. megalodon was not simply a supersized great white, but what kind of shape the enormous shark took as it slid through ancient waters is only just beginning to come into focus.
www.smithsonianmag.com/science-nature/was-megalodon-slimmer-than-previously-thought-180983628/