Cooler waters created super-sized Megalodon
Megalodon expert leads the discovery of an intriguing pattern of the prehistoric shark

Date:
March 7, 2022
Source:
Taylor & Francis Group
Summary:
A new study reveals that the iconic extinct Megalodon or megatooth
shark grew to larger sizes in cooler environments than in warmer
areas.



FULL STORY ==========================================================================
A new study reveals that the iconic extinct Megalodon or megatooth shark
grew to larger sizes in cooler environments than in warmer areas.


========================================================================== DePaul University paleobiology professor Kenshu Shimada and coauthors
take a renewed look through time and space at the body size patterns of
Otodus megalodon, the fossil shark that lived nearly worldwide roughly
15 to 3.6 million years ago. The new study appears in the international
journal Historical Biology.

Otodus megalodon is commonly portrayed as a gigantic, monstrous shark
in novels and films, such as the 2018 sci-fi thriller "The Meg." In
reality, this species is only known from teeth and vertebrae in the
fossil record, although it is generally accepted scientifically that
the species was indeed quite gigantic, growing to at least 50 feet
(15 meters) and possibly as much as 65 feet (20 meters). The new study re-examined published records of geographic occurrences of Megalodon
teeth along with their estimated total body lengths.

"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," said Shimada.

Introduced by a German biologist Carl Bergmann in the mid-1800s,
Bergmann's rule is a broad generalization explaining that larger animals
thrive in cooler climates because their size helps them retain heat
more efficiently compared to animals with smaller bodies. "Scientists constantly search for rules of life that help us predict natural patterns,
and it seems that Bergmann's rule applied to Otodus megalodon," noted
coauthor Victor Perez, a paleontologist at the Calvert Marine Museum
in Maryland.

Some Megalodon sites were previously identified as possible nursery
areas of the fossil shark because 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. "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,"
said coauthor Harry Maisch, a faculty member at Bergen Community College
and Fairleigh Dickinson University in New Jersey.

"The idea of this new study originated from 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?" said coauthor Martin Becker, a professor of environmental
science at William Paterson University in New Jersey. Despite being
initiated by this simple question, "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," noted coauthor Michael Griffiths and
another professor of environmental science at William Paterson University.

"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," said Shimada.

========================================================================== Story Source: Materials provided by Taylor_&_Francis_Group. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Kenshu Shimada, Harry M. Maisch, Victor J. Perez, Martin A. Becker,
Michael L. Griffiths. 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.

Historical Biology, 2022; 1 DOI: 10.1080/08912963.2022.2032024 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220307082337.htm

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