The size and shape of Megalodon's body reveal why some aquatic creatures are capable of gigantism.
The biology of the megalodon (megatooth shark), a prehistoric giant shark
that roamed almost everywhere between 15 and 3.6 million years ago,
is revealed in a new study. Along with 28 other experts from across the world in shark, fossil,
and vertebrate anatomy, the study was directed by Kenshu Shimada,
a professor of paleobiology at DePaul University. The study's results have been published in the Palaeontologia Electronica
journal.
Formally named as Otodus megalodon, it has no complete skeletons
known to science and is mostly identified by its scales, vertebrae,
and serrated teeth in the fossil record. Despite being significantly smaller, the great white shark of today
Because (Carcharodon carcharias) also possessed serrated teeth,
it has long been believed that the prehistoric shark superficially resembled
a giant great white shark in both earlier research and science fiction
movies like "The Meg."
However, a virtually entire fossilized spinal column (the trunk section)
of O. megalodon, which was approximately 11 meters (36 feet) long,
has been thoroughly studied in Belgium. The straightforward issue posed by the new study was: How long were
the portions that were absent from the vertebral column
specimen—specifically, the lengths
of the O. megalodon individual's head and tail?
The team of researchers, who came from Australia, Austria, Brazil, France,
Italy, Japan, Mexico, the U.K., and the U.S., examined the proportions
of the head, trunk, and tail in relation to the overall body length of 145 living
shark species and 20 extinct ones in order to answer the issue. The scientists concluded that O. megalodon's head and tail lengths might
have made up roughly 16.6% and 32.6% of its overall body length, respectively,
assuming that it had a body plan similar to that of the great majority of sharks.
Given that the Belgian trunk vertebral specimen is 11 meters long,
the estimated length of the individual O. megalodon is 16.4 meters (54 feet),
with the head and tail measuring around 1.8 meters (6 feet) and 3.6 meters
(12 feet), respectively.
Although putative O. megalodon vertebrae from Denmark have been reported
to have a diameter of up to 23 centimeters (9 inches), the largest vertebra
of the Belgian species is 15.5 centimeters (6 inches). That person might have been around 24.3 meters (80 feet) long if the Danish
vertebrae are the largest in the body.
Shimada, a member of the Department of Environmental Science and Studies
and Department of Biological Sciences at DePaul University, stated that
the length of 24.3 meters is currently the largest reasonable estimate
for O. megalodon that can be justified based on science and
the current fossil record.
Shimada and his colleagues' investigation went farther. They concluded that the body form of O. megalodon probably superficially
resembled the present lemon shark (Negaprion brevirostris),
which has a more slender body than the modern great white shark,
based on comparisons of the proportions of their body parts. The team also observed that many of the giant aquatic vertebrates,
including whales (Cetacea), have slender bodies because large stocky
bodies are hydrodynamically inefficient for swimming.
Examples of these sharks are the basking shark (Cetorhinus maximus)
and the whale shark (Rhincodon typus).
On the other hand, due to hydrodynamic limitations, the great white shark,
which has a stocky body that gets more stockier as it grows, can be massive
but cannot be enormous (no more than 7 meters or 23 ft). The implications are significant since the team has finally solved
the puzzle of why some aquatic animals may grow to enormous
sizes while others cannot.
Phillip Sternes and Jake Wood, two of Shimada's former DePaul University
master's students, were also on the research team.
Sternes, who is currently an educator at SeaWorld San Diego, stated,
"Our new study has confirmed the view that O. megalodon was not only
a huge version of the modern-day great white shark, validating our prior work."
"The utilization of a completely unique approach that does not simply
rely on the modern great white shark is what sets our work apart from
all previous articles on body size and form estimations of O. megalodon,"
continued Wood, who is currently pursuing a doctorate
at Florida Atlantic University in Boca Raton, Florida.
Other biological elements were also reevaluated in the new study.
A 24.3-meter-long O. megalodon, for instance,
would have weighed around 94 tons and traveled at a cruising speed
of 2.1 to 3.5 kilometers (1.3 to 2.2 miles) per hour, which is no quicker
than the great white shark of today. This estimate was based
on scale morphology. According to the growth patterns found in the Belgian vertebral
specimen, O. megalodon gave birth to living offspring that were
between 3.6 and 3.9 meters (12 and 13 feet) long, and the embryos
fed themselves by eating eggs.
Together with the known fossil record of O. megalodon and the white shark
lineage, additional recently inferred growth patterns provide credence
to the theory that competition from the great white shark's emergence
about 5 million years ago contributed to O. megalodon's eventual mortality.
In the hopes that a complete skeleton will one day be found so that
the interpretations can be tested, Shimada stated, "Many of the conclusions
we made are still questionable, but they are data-driven and will serve
as reasonable reference points for future studies on the biology
of O. megalodon."
Source phys.org
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