Otodus megalodon, the largest shark that ever lived on Earth, most certainly reached at least 15 m (50 feet) in total length based on its gigantic teeth. Besides teeth, the species is also known from some isolated and associated vertebral specimens. It is entirely possible that the ancient shark could have indeed resembled the living great white shark (Carcharodon carcharias) or lamnid sharks. However, according to the new research by paleontologists from the University of California at Riverside, DePaul University, and the Fort Hays State University’s Sternberg Museum of Natural History, the body form of Otodus megalodon can only be speculated based on the present fossil record, where there are no scientific means to decisively support or refute the accuracy of any of the previously published body forms of the fossil species.
Otodus megalodon is an extinct species of mackerel shark that lived from the middle Miocene to the Pliocene, approximately 15 to 2.6 million years ago.
This prehistoric monster likely reached lengths of at least 15 m and possibly as much as 20 m (65 feet).
Otodus megalodon was a top-level predator that fed on whales and other marine mammals.
It had a cartilaginous skeleton and was therefore poorly preserved with exception of its teeth, but paleontologists believe that it looked a lot like the great white shark, only far larger.
“The great white shark belongs to the family Lamnidae (lamnids), also including the mako, porbeagle, and salmon sharks, and they are regionally endothermic (partially warm-blooded), allowing them to be active predators,” said Professor Kenshu Shimada, a paleobiologist in the Department of Environmental Science and Studies and the Department of Biological Sciences at DePaul University and the Sternberg Museum of Natural History.
“Otodus megalodon is not a lamnid shark, but it was previously inferred to also have been regionally endothermic.”
Based on the inference, yet another previous study used 2D geometric shape analyses on the body forms of modern lamnids to propose an inferred body form of Otodus megalodon.
Professor Shimada and colleagues examined whether such a two-dimensional approach can actually differentiate the body forms represented by modern endothermic (warm-blooded) species from those of modern ectothermic (cold-blooded) ones within the shark order called Lamniformes, which also includes Otodus megalodon.
The study strongly indicates that, two-dimensionally, there is no relationship between thermophysiology and body form in lamniforms.
“Although it is still possible that Otodus megalodon could have resembled the modern great white shark or lamnids, our results suggest that the two-dimensional approach does not necessarily decisively allow the body form reconstruction for Otodus megalodon,” said Jake Wood, a graduate student in the Department of Evolution, Ecology, and Organismal Biology at the University of California at Riverside.
“All previously proposed body forms of Otodus megalodon should be regarded as speculations from the scientific standpoint,” added Phillip Sternes, a Ph.D. candidate at the University of California at Riverside.
“Any meaningful discussion about the body form of Otodus megalodon would require the discovery of at least one complete, or nearly complete, skeleton of the species in the fossil record,” Wood noted.
“The fact that we still don’t know exactly how Otodus megalodon looked keeps our imagination going,” Professor Shimada said.
“This is exactly why the science of paleontology continues to be an exciting academic field. We’ll continue looking for more clues in the fossil record.”
The team’s paper appears in the journal Historical Biology.
Phillip C. Sterne et al. Body forms of extant lamniform sharks (Elasmobranchii: Lamniformes), and comments on the morphology of the extinct megatooth shark, Otodus megalodon, and the evolution of lamniform thermophysiology. Historical Biology, in press; doi: 10.1080/08912963.2021.2025228
Source link: https://www.sci.news/paleontology/megalodon-body-forms-10527.html