New research bites holes into theories about Megalodons
Extinct shark's shape swims back out of focus

Date:
February 7, 2022
Source:
University of California - Riverside
Summary:
A new study leaves large tooth marks in previous conclusions about
the body shape of the Megalodon, one of the largest sharks that
ever lived.



FULL STORY ==========================================================================
A new study leaves large tooth marks in previous conclusions about the
body shape of the Megalodon, one of the largest sharks that ever lived.


==========================================================================
The study, which makes use of a pioneering technique for analyzing sharks,
has now been published in the international journal Historical Biology.

Megalodons swam the Earth roughly 15 to 3.6-million years ago, and are
often portrayed as super-sized monsters in films such as 2018's "The
Meg." While there is no dispute that they existed or that they were
gigantic, Otodus megalodon are known only from their fossilized teeth
and vertebrae. Based on this evidence, studies suggest they reached
lengths of up to 65 feet.

Unfortunately, additional fossil evidence from which to draw conclusions
about their bodies, such as a complete skeleton, has not yet been
discovered.

"The cartilage in shark bodies doesn't preserve well, so there are
currently no scientific means to support or refute previous studies
on O. megalodon body forms," said Phillip Sternes, a UCR organismal
biologist and lead author on the study.

Traditionally, researchers have modeled Megalodon bodies on those of
modern great white sharks. Great whites are partially warm blooded and
belong to the lamniform shark order. Megalodons also belong to this
order, and it is believed they shared this partial warm bloodedness with
great whites.



==========================================================================
It was previously thought having some warm blood is an advantage that
could expand sharks' swimming range, unlike other fish dependent on
water temperature. However, it is now believed to increase swimming speed.

"Great whites are among the fastest swimming sharks, so Megalodons were
likely also big, fast sharks you would not want to run into in the open
ocean," said Sternes.

There are eight families of Lamniformes, and 15 species. Previous research
took five species of warm-blooded Lamniformes, averaged their fin and
body shapes and proposed a general model for Megalodons.

Sternes and his colleagues wanted to understand whether the five species
used to determine Megalodon's shape differed somehow from the rest of
the order, which includes some sharks that are cold blooded.

The researchers compared the five species to each other, and to the
rest of the lamniform order. Using detailed field guide drawings,
they performed quantitative comparisons of the sharks' fin, head and
body shapes.



==========================================================================
They found no general patterns that would allow them to tease out body
shape differences.

"Warm bloodedness does not make you a differently shaped shark,"
Sternes said.

"I encourage others to explore ideas about its body shape, and to search
for the ultimate treasure of a preserved Megalodon fossil. Meanwhile,
this result clears up some confusion about previous findings and opens
the door to other ideas once again." While others typically use actual organisms or photos of organisms for such comparisons, Sternes pioneered
the use of this two-dimensional drawing technique on sharks.

"The purpose of field guides is to identify a species, so the drawings
must be accurate representations," he said. "It's a technique widely used
in biology and works well for sharks since some specimens exist only in
remote places." Sternes hopes that others use the technique to study
snakes, birds and other animals with specimens that may be difficult
to collect. He also hopes others will continue to search for a better understanding of the Megalodon.

"This study may appear to be a step backward in science," said
Kenshu Shimada, study co-author and DePaul University paleobiology
professor. "But the continued mystery makes paleontology, the study
of prehistoric life, a fascinating and exciting scientific field." ========================================================================== Story Source: Materials provided by
University_of_California_-_Riverside. Original written by Jules
Bernstein. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Phillip C. Sternes, Jake J. Wood, Kenshu Shimada. 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,
2022; 1 DOI: 10.1080/08912963.2021.2025228 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220207083443.htm

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