Wednesday, May 18, 2022

Megalodon shark grew to larger sizes due to cooler environments

It seems that Bergmann's rule applied to Otodus megalodon.

Megalodon shark is one of the largest predators to have ever lived. It is known mainly for its gigantic teeth and possibly reached 18–20 m in total length (TL).

This late Neogene megatooth shark, Otodus megalodon, lived nearly worldwide roughly 15 to 3.6 million years ago. Now, scientists in a new study took a renewed look through time and space at the body size patterns of Otodus megalodon. They reexamined published records of geographic occurrences of Megalodon teeth along with their estimated total body lengths.

The study suggests that the iconic extinct Megalodon or megatooth shark grew larger in cooler environments than in warmer areas.

DePaul University paleobiology professor Kenshu Shimada said, “Our findings suggest a previously unrecognized body size pattern for the fossil shark, notably following a geography-driven ecological pattern known as Bergmann’s rule.”

According to Bergmann’s rule, larger animals thrive in cooler climates because their size helps them retain heat more efficiently than animals with smaller bodies.

Coauthor Victor Perez, a paleontologist at the Calvert Marine Museum in Maryland, said, “Scientists constantly search for rules of life that help us predict natural patterns, and it seems that Bergmann’s rule applied to Otodus megalodon.”

Scientists have previously identified possible nursery areas of the fossil shark. Those sites yield smaller Megalodon teeth on average relative to other Megalodon localities.

However, the new study found that the previously identified nursery areas for Megalodon are located near the equator, where water is warmer.

Harry Maisch, a faculty member at Bergen Community College and Fairleigh Dickinson University in New Jersey, said, “It is still possible that O. megalodon could have utilized nursery areas to raise young sharks. But our study shows that fossil localities consisting of smaller Megalodon teeth may instead be a product of individual sharks attaining smaller overall body sizes simply as a result of warmer water.”

Martin Becker, a professor of environmental science at William Paterson University in New Jersey, said, “The idea of this new study originated from a casual conversation that took place during a recent fishing trip to the Florida Keys by the lead author, his family, and me, stemming from a basic question: where do large fish live?”

Michael Griffiths and another professor of environmental science at William Paterson University said“The results of this study have important implications for understanding how modern climate change is rapidly accelerating marine habitat shifts to more polar latitudes in apex predators such as sharks.”

DePaul University paleobiology professor Kenshu Shimada said, “The main conclusion of this study is that not all geographically different Megalodon individuals grew to gigantic sizes equally. The common notion that the species reached 18–20 m TL should be applied primarily to populations that inhabited cooler environments.”

Journal Reference:

  1. Kenshu Shimada et al. Revisiting body size trends and nursery areas of the Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), reveals Bergmann’s rule possibly enhanced its gigantism in cooler waters. DOI: 10.1080/08912963.2022.2032024

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