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Terça-feira, Maio 17, 2022

Ninguém sabe realmente como era o tubarão gigante

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Ilustração do Megalodonte

Ilustração do artista do Megalodon. No entanto, novas pesquisas científicas mostram que ninguém sabe como o Megalodon realmente se parecia.

O estudo mais recente revela que ninguém ainda sabe como o Megalodon realmente se parecia. Pesquisadores de tubarões da Universidade DePaul dizem que o mistério torna a paleontologia um campo científico empolgante.

Um novo estudo científico mostra que todas as formas corporais propostas anteriormente do gigantesco Megalodon, ou tubarão megadente, que viveu quase em todo o mundo cerca de 15 a 3,6 milhões de anos atrás, permanecem no reino das especulações.

“O estudo pode parecer um retrocesso na ciência, mas o mistério contínuo torna a paleontologia, o estudo da vida pré-histórica, um campo científico fascinante e emocionante”, disse Kenshu Shimada, professor de paleobiologia da Universidade DePaul e coautor do estudo. Esta última pesquisa lança luz sobre a realidade sobre a compreensão atual da forma do corpo do Megalodon (formalmente chamado de Otodus megalodon) aparece na revista internacional Biologia Histórica.

Otodus megalodon é tipicamente retratado como um tubarão gigante e monstruoso em romances e filmes como o filme de ficção científica de 2018 “The Meg”. Estudos anteriores sugerem que o tubarão provavelmente atingiu comprimentos de pelo menos 15 metros (50 pés) e possivelmente até 20 metros (65 pés).

“Este novo estudo mostra que atualmente não existem meios científicos para apoiar ou refutar a[{” attribute=””>accuracy of any of the previously published body forms of O. megalodon,” noted lead author Phillip Sternes, who graduated from DePaul in 2019 and is currently a Ph.D. candidate at the University of California, Riverside. Shimada mentored Sternes in his DePaul lab in Chicago, and the new study additionally includes Shimada’s current graduate student, Jake Wood, as coauthor.

Kenshu Shimada Megalodon Shark Tooth

Paleobiologist Kenshu Shimada (DePaul University, Chicago) holds a tooth of an extinct shark Otodus megalodon, or the so-called “Meg” or megatooth shark. (DePaul University/Jeff Carrion). Credit: DePaul University/Jeff Carrion

Otodus megalodon is known only from its teeth and vertebrae in the fossil record, and traditionally the modern great white shark (Carcharodon carcharias) was used as a model for the body form of O. megalodonCarcharodon carcharias belongs to the shark family Lamnidae, or lamnids, also including the mako, porbeagle, and salmon sharks, and they are regionally endothermic (partially warm-blooded), allowing them to be active predators. 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 two-dimensional geometric shape analyses on the body forms of modern lamnids to propose an inferred body form of O. megalodon.

The new study by Sternes, Wood and Shimada 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 O. 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 O. megalodon,” Wood said.

“All previously proposed body forms of Otodus megalodon should be regarded as speculations from the scientific standpoint,” Sternes said. “Any meaningful discussion about the body form of O. megalodon would require the discovery of at least one complete, or nearly complete, skeleton of the species in the fossil record,” added Wood. “The fact that we still don’t know exactly how O. megalodon looked keeps our imagination going,” 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.”

Reference: “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” 6 February 2022, Historical Biology.
DOI: 10.1080/08912963.2021.2025228





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